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Introduction to Digital Computers

1. 4 8 4 9 The first computers were designed to manipulate numbers to solve arithmetic problems True 2 False What is data to be represented called Numeric data 2 Alphanumeric data 3 Information data 4 Source data Raw data is typically written on some type of paper document referred to as what type of document End document 2 Source document 3 Classified document 4 Unclassified document Numeric alphabetic and special characters are represented in a computer s internal storage and on magnetic media through the use of what kind of system 1 Coding 2 Reading 3 Writing 4 Labeling It is possible to represent a maximum of 256 different characters or bit combinations by using which of the following codes 1 8 bit 2 16 bit 3 32 bit 4 64 bit In addition to four numeric bits there are four other bit positions used in an a bit code what are they called 1 Area bits 2 Zone bits 3 Region bits 4 District bits 4 11 Which of the following numbering systems has a base of 16 1 Octal 2 Binary 3 Decimal 4 Hexadecimal 4 12 Representing two numeric characters in one byte eight bits is referred to as what 1 Packing 2 Stacking 3 Doubling 4 Crowding 4 13 By packing data within an 8 bit code which of the following results are achieved 1 Storage space required increases and processing speed increases 2 Storage space required increases an
2. Control instructions are used to send commands to devices not under direct command of the control section such as input output units or devices ARITHMETIC LOGIC SECTION The arithmetic logic section performs all arithmetic operations adding subtracting multiplying and dividing Through its logic capability it tests various conditions encountered during processing and takes action based on the result As indicated by the solid arrows in figure 2 1 data flows between the arithmetic logic section and the internal storage section during processing Specifically data is transferred as needed from the internal storage section to the arithmetic logic section processed and returned to the internal storage section At no time does processing take place in the storage section Data may be transferred back and forth between these two sections several times before processing is completed The results are then transferred from internal storage to an output unit as indicated by the solid arrow fig 2 1 2 3 MEMORY INTERNAL STORAGE SECTION All memory internal storage sections must contain facilities to store computer data or instructions that are intelligible to the computer until these instructions or data are needed in the performance of the computer calculations Before the stored program computer can begin to process input data it is first necessary to store in its memory a sequence of instructions and tables of constants and other dat
3. A low level machine oriented programming language in which each instruction written as a mnemonic translates into a single machine language computer instruction AUTOMATIC DATA PROCESSING ADP A general term used to define a system for automatically performing a series of data processing functions by means of machines using mechanical electromechanical and electronic circuitry AUXILIARY EQUIPMENT The peripheral equipment or devices that may or may not be in direct communication with the central processing unit of a computer AUXILIARY STORAGE See storage secondary BACKUP FILE A copy of a program or data file to be used in the event something happens to the original BASIC Beginners All Purpose Symbolic Instruction Code A high level general purpose programming language primarily used on microcomputers See NAVEDTRA 10079 Introduction to Programming in BASIC BAUD A unit for measuring data transmission speed For practical purposes it is now used interchangeably with bits per second as the unit of measure of data flow AI 1 BINARY Two values 0 or 1 or states ON or OFF the number system used in computers BIT An abbreviation for binary digit the smallest unit of data either a O or 1 BLOCKED RECORDS One or more logical records grouped and treated as a unit physical record or block for input output processing BLOCKING FACTOR The number of records stored in a record block BOOT OR BOOT
4. Spelling checkers mailing list programs document compilation programs and communications programs Data management They are tables of rows and columns of numbers No 3 29 CHAPTER 4 DATA REPRESENTATION AND COMMUNICATIONS LEARNING OBJECTIVES Upon completion of this chapter you will be able to do the following 1 Explain data and how it is represented 2 Explain computer coding systems 3 Define a parity bit and what it is used for 4 Explain data storage concepts 5 Describe three storage access methods 6 Describe networks and data communications INTRODUCTION One of the major problems we face in using a digital computer is communicating with it We must have one or more ways of getting data into the computer to be processed You learned in chapter 2 that there are several types of input devices that read data into a computer But how does one prepare the data to be used as input How do we convert human readable documents into a computer readable form and what type of input media do we use If the data is to be used by another computer some distance away how do we transmit it Well as you probably suspect there are several ways to perform this conversion and transmission process and that is the chapter of our discussion DATA Data is a general term used to describe raw facts To put it simply data is nothing more than a collection of related elements or items that when properly coded into some type of input
5. 2 1426 2 Electrical 3 1462 3 Analog 4 1642 4 Electromechanical What year did electronics enter the 1 7 What determines the size of an analog computer scene computer 1 1918 1 Where it will be installed 2 1919 2 Number of operators using it 3 1920 3 Cost 4 1921 4 Number of functions it has to perform In modern digital computers circuits that store information perform arithmetic 1 8 What is the primary use of analog operations and control the timing computers in the Navy sequences are known as what 1 Gun fire control 1 Flip flops 2 Data processing 2 Amplifiers 3 Ships steering 3 Oscillators 4 Missile fire control 4 Multipliers 1 9 Compared to mechanical computers When was the UNIVAC I developed electromechanical computers are different in which of the following ways 1 1944 2 1946 1 They cost more 3 1950 2 They are bigger 4 1951 3 They are less accurate 4 They use electrical components to The field of research that is developing perform some of the calculations and computer systems which mimic human to increase the accuracy thought in a specific area and improve performance with experience and 1 10 In early electronic computers what was operation is what field of research the weak link in electrical computations 1 Human intelligence 1 Transistors 2 Artificial intelligence 2 Resistors 3 Animal intelligence 3 Vacuum tubes 4 Computer intelligence 4 Capacitors 1 11 A c
6. Figure 2 10B Physical organization of data on a disk SECTOR METHOD 2 12 MAGNETIC TAPE Another type of storage device is magnetic tape which is similar to the tape used with commercial tape recorders It is used mainly for secondary storage It differs from commercial tape in that it is usually wider ranging from one half inch to an inch and it is manufactured to more rigid quality specifications It is made ofa MYLAR base coated with a magnetic oxide that can be magnetized to store data Magnetic tape comes in a variety of lengths from 600 to 3 000 feet and is packaged in one of three ways open reel cartridge or cassette as shown in figure 2 11 Large computers use standard open reels 1 2 inch wide tape 2 400 feet in length Magnetic tape units are categorized by the type of packaging used for the tape The tape unit or drive shown in figure 2 12 uses open reels while cartridge tape units use tape cartridges and cassette units use tape cassettes Cartridge tape units are often used on personal computers to provide backup for hard disk CASSETTE Figure 2 11 Various types of magnetic tape storage 2 13 Figure 2 12 Mounting a magnetic tape A standard 1 2 inch tape may have either seven fig 2 13 view A or nine tracks fig 2 13 view B of data stored on it depending upon the particular read write heads installed in the tape unit Read write heads are usually designed to read or write data in the fo
7. 1 document identification 2 stock number 3 unit of issue 4 quantity and so on You ll notice we need more than numbers and that is where coding systems come into play L iex VLLL ACTIN Y i E Lum j USS JORN PAUL JONES DDC 3 d A a Do TT QR oe denas e op D CTE ST S 00 161 6219 SPONCE 26 2 60 ENOL l 100 205 0510 MANIFOLD CREEN 12 20 ENOL 100 205 0512 MANIFOLD WHITE 12 20 ENOL Figure 4 2 SERVMART shopping list source document Q 1 What is a general term used to describe raw facts Q 2 How is data represented Q 3 What were the first computers designed to manipulate in order to solve arithmetic problems Q 4 By what two means can the data contained on a source document be converted into a machine readable form for processing Q 5 What are some of the types of input media on which data may be indirectly entered COMPUTER CODING SYSTEMS To represent numeric alphabetic and special characters in a computer s internal storage and on magnetic media we must use some sort of coding system In computers the code 1s made up of fixed size groups of binary positions Each binary position in a group is assigned a specific value for example 8 4 2 or 1 In this way every character can be represented by a combination of bits that is different from any other combination In this section you will learn how the selected coding systems are use
8. 3 26 TOTAL Cost 5 1231 50 3150 00 70 00 T4 00 148 00 4535 50 B BAR CHART Figure 3 11B Graphics examples BAR CHART You cannot use all printers for graphics output They must be capable of producing graphics and also be compatible with the software Some character printers can be used for limited graphics Dot matrix printers and plotters work well for graphics output Laser and ink jet printers are also good for both text and graphics Q 29 What is packaged software Q 30 What are some of the other features and software available with a word processing sofiware package Q 31 What software allows you to enter data and then retrieve it in a variety of ways Q 32 What are spreadsheets Q 33 Are all printers capable of handling graphics output SUMMARY Congratulations you have just finished chapter 3 By now you should be convinced that anyone with a little study can understand digital computers You probably thought when you first started this NEETS MODULE that it would get more difficult as your studies progressed Our objective was to show you that the more you learn the easier the material is to understand OPERATING SYSTEMS are a collection of many programs used by the computer to manage its own resources and operations and to perform commonly used functions like copy print and so on UTILITY PROGRAMS perform such tasks as sorting merging and transferring copying data from one input output dev
9. First generation computers were characterized by what technology Transistors Resistors Vacuum tubes Printed circuits Tour What type of computer language was used with first generation computers 1 Machine 2 COBOL 3 BASIC 4 Fortran Computers of the second generation were characterized by what technology 1 Vacuum tubes 2 Capacitors 3 Transistors 4 Resistors 1 22 The small long lasting transistors used in 1 23 1 24 1 25 1 26 second generation computers had which of the following effects 1 They increased processing speeds and reliability 2 They decreased processing speeds and increased reliability 3 They increased processing speeds and decreased reliability 4 They decreased processing speeds and reliability Internal processing speeds of second generation computers were measured at what speed Hundredths of a second Thousandths of a second Millionths of a second Billionths of a second Third generation computers characterized by what technology 1 Capacitors 2 Transistors 3 Resistors 4 Miniaturized circuits A circuit and its components can be etched onto which of the following materials 1 Plastic 2 Silicon 3 Gold 4 Pressed fiber The internal processing speeds of third generation computers are measured at what speed Hundredths of a second Thousandths of a second Millionths of a second Billionths of a second Pe
10. How many systems dealing with accounting applications have been widely accepted Q 44 What does the acronym S N A P stand for Q 45 For what purposes is the SNAP II system designed Q 46 What does user friendly mean in computer terms Q 47 What does a password prevent Q 46 In the SNAP Il system how are the different levels of entry defined Q 49 The work center supervisor can update what items from a user terminal Q 50 At present what type of classified use is allowed for SNAP II USING A DESKTOP COMPUTER To use a desktop personal computer effectively you ll need to learn about the hardware the equipment and the software the programs You will also need to know how to handle disks and how to back up programs and data files So let s assume you have a desktop computer system to use Its hardware consists of a display screen a keyboard a computer two floppy disk drives A amp B and a printer Look at the example in figure 1 12 You need software computer programs to make the computer operate The first program you need is the operating system The operating system manages the computer and allows you to run application programs like word processing or recordkeeping programs So let s begin with the operating system Figure 1 12 Typical microcomputer system with display keyboard floppy disk drives and printer OPERATING SYSTEM An operating system is simply a set of programs and routines that lets you and ot
11. These are the ones commonly used with personal computers 2 24 OPERATING PANEL POWER CABLE CONNECTOR Figure 2 23 Printer Daisy Wheel Printers Daisy wheel printers have the most professional looking pleasing to the eye print of all the printers in the character at a time impact printer class Daisy wheel printers are often used in an office or word processing environment where crisp sharp high quahty letter quality characters are a must The daisy wheel printer uses a round disk with embossed characters located at the end of each petal like projection one character per petal similar to the petals of a daisy as shown in figure 2 24 A drive motor spins the wheel at a high rate of speed When the desired character spins to the correct position the print hammer strikes that character causing it to be printed on the paper Once printed the daisy wheel continues to move searching out the next character to be printed until the line is completed The speeds of daisy wheel printers range from 30 to 60 characters per second cps Figure 2 24 A daisy wheel print wheel Dot Matrix Printers Dot matrix printers also known as the wire matrix printers create characters in much the same way you see numbers on the scoreboard at a baseball or football game In contrast to the daisy wheel printers dot matrix printers use an arrangement of tiny pins or hammers called a dot matrix to generate characters a dot at a time A d
12. Where is specific information about the computer you are to use contained Q 27 How do we refer to errors caused by faulty logic and coding mistakes Q 28 What is the purpose of testing a program 3 22 PACKAGED SOFTWARE Fortunately you don t have to write a program for every problem to be solved Instead you can use packaged or off the shelf programs that are designed for specific classes of applications Everyday more and more packaged software software written by the manufacturer a software house or central design agency CDA becomes available for general use It may be up to you to set up and process a job within the specifications of a packaged program Let s look at four classes of packaged software you may work with word processing data management spreadsheets and graphics WORD PROCESSING You can use word processing software for any function that involves text letters memos forms reports and so on At a minimum it includes routines for creating editing storing retrieving and printing text Under the word processing software control you generally enter the text on the keyboard and it is printed on a display screen as shown in figure 3 8 At that point you may store it on disk or tape print it on a printer or change edit it Using the edit functions you can add or delete words characters lines sentences or paragraphs You can rearrange text for example move a paragraph or block of information to another p
13. Which computer is used with the SNAP II system 1 UYK 4 2 UYK 7 3 UYK 20 4 AN UYK 62 V Where are the user terminals for SNAP II placed on board ship Engineering spaces 2 Work centers 3 Supply spaces 4 Electronics spaces The work center supervisor can update which of the following items from a user terminal 1 COSAL APL EIC and CSMP only 2 APL EIC SHIP S FORCE WORK LIST and CSMP only 3 COSAL APL SHIP S FORCE WORK LIST and CSMP only 4 COSAL APL EIC SHIP S FORCE WORK LIST and CSMP 1 37 1 38 1 39 1 40 1 41 What type of classified use does SNAP II allow 1 Unclassified 2 Confidential 3 Secret 4 Top Secret What is a central set of programs called that manages execution of other programs and performs common functions like read write and print 1 Managing system 2 Execution system 3 Operating system 4 Word processing system What is the function of a built in program called a bootstrap loader 1 To load a word processor into the computer s internal memory 2 To load an external operating system into the computer s internal memory 3 To load a graphics program into the computer s internal memory 4 To load a bootstrap program into the computer s internal memory When an error message such as device error is shown on the display screen which of the following problems could be the cause 1 No floppy disk in drive A Floppy dis
14. fig 4 11 The following definitions should help you understand the relationship between bits characters bytes words fields records and files CHARACTER CHARACTER LAST 1 2 CHARACTER ii FIELD FIELD LAST FIELD FIELD LAST FIELD FIELD LAST 1 2 FIELD 1 2 FIELD 1 2 FIELD spen gt ema met emnes un e RECORD 1 RECORD 2 LAST RECORD Figure 4 11 Data organization BIT The smallest unit of data it represents one binary digit 0 or 1 CHARACTER BYTE A group of related bits usually eight that make up a single character letter number or special character WORD A group of related bytes that are treated as a single addressable unit or entity in memory FIELD One or more related characters that are treated as a unit of information A field also referred to as a data item may be alphabetic numeric or alphanumeric and may be either fixed or variable in length For example your social security number SSN is of a fixed length that is it s always 9 positions in length Whereas names are variable length because they may be from 2 to 25 positions in length RECORD A group of related fields all pertaining to the same subject a person a thing or an event For example your payroll record LES statement might include fields for your name amount paid taxes withheld earned leave and any allotments you might have On the other hand a supply inventory record might consist of fields con
15. following ranges of speeds in characters per second 1 50to 200 cps 2 60 to 350 cps 3 70 to 400 cps 4 80 to 450 cps 2 63 2 64 2 65 2 66 2 67 Ink jet printers have what maximum 2 68 speed in characters per seconds 1 300 cps 2 400 cps 3 500 cps 4 600 cps Laser printers can print up to 2 69 approximately what total number of characters per second 1 20 666 cps 2 22 666 cps 3 24 666 cps 4 26 666 cps What are the two styles of typewriter keyboard arrangements used with a computer 2 70 1 QWERYT or DVORAK 2 QWERTY or DVORAK 3 ABCDEFor DVORAK 4 ABCDEFor DVOARK When working with display devices what does the term soft copy mean 1 The information displayed is not 2 71 permanent 2 The information displayed is permanent 3 The information displayed has a soft glow 4 The information displayed has no glow On a raster scan crt a raster is a series of 2 72 what type of lines across the face of a crt 1 Diagonal 2 Vertical 3 Horizontal 4 Wavy 13 Each field of a raster scan crt is made up of approximately how many lines 1 525 2 550 3 575 4 600 In a video monitor what do the frequency bandwidth the number of characters to be displayed on a line and the physical size of the screen determine Actual level of brightness Actual number of picture elements Actual speed of scan rate Actual number of vertical lines that can be displayed X pal A monitor tha
16. for program completeness Typical input data should be manually traced through the program processing paths to identify possible errors In effect you will be attempting to play the role of the computer After you have desk checked the program for accuracy the program is ready to be assembled or compiled Assembly and compiler programs prepare your program source program to be executed by the computer and they have error diagnostic features which detect certain types of mistakes in your program These mistakes must be corrected Even when an error free pass of the program through the assembly or compiler program is accomplished this does not mean your program is perfected However it usually means the program is ready for testing Testing Once a program reaches the testing stage generally it has proved it will run and produce output The purpose of testing is to determine that all data can be processed correctly and that the output is correct The testing process involves processing input test data that will produce known results The test data should include 1 typical data which will test the commonly used program paths 2 unusual but valid data which will test the program paths used to process exceptions 3 incorrect incomplete or inappropriate data which will test the program s error routines If the program does not pass these tests more testing is required You will have to examine the errors and review the coding to make the co
17. you are ready to develop a flowchart showing the logic steps and sequence of steps you want the computer to execute to solve the problem A programming flowchart of this problem is also shown in figure 3 6 Study both the problem definition and the flowchart to see their relationship and content You now have a plan of what you want the computer to do The next step is to code a program that can be translated by a computer into a set of instructions it can execute This step is called program coding PROGRAM CODING It is important to remember program coding is not the first step of programming Too often we have a tendency to start coding too soon As we just discussed a great deal of planning and preparation must be done before sitting down to code the computer instructions to solve a problem For the example amortization problem fig 3 6 we have analyzed the specifications in terms of 1 the output desired 2 the operations and procedures required to produce the output and 3 the input data needed In conjunction with this analysis we have developed a programming flowchart that outlines the procedures for taking the input data and processing it into usable output You are now ready to code the instructions that will control the computer during processing This requires that you know a programming language All programming languages FORTRAN COBOL BASIC and so on are composed of instructions that enable the computer to process a part
18. 1 27 1 28 1 29 1 30 1 31 Fourth generation technology has which of the following results for the computer industry 1 Computers that are significantly smaller and lower in cost 2 Computers that are significantly larger and lower in cost 3 Computers that are significantly smaller and higher in cost 4 Computers that are significantly larger and higher in cost What does the acronym ROM stand for Run on manual Read only minutes Read only memory Read only manual de Iu Which of the following will be one of the future challenges involving computer power 1 How to properly and effectively use the computing power available 2 How to increase computer storage capacity 3 How to increase computer power 4 How to properly install the computers available What term is used for programs such as assemblers compilers operating systems and applications programs 1 Hardware 2 Peripheral devices 3 Software 4 Sub systems Which of the following is one of the more widespread uses of the computer in the Navy 1 Research 2 Word processing 3 Manufacturing 4 Games 1 32 Computers have an advantage over typewriters in what area 1 Cost 2 Speed 3 Reliability 4 Correcting errors What does the acronym S N A P stand for 1 Shipboard navigational aid package 2 Shipboard Navy applied program 3 Shipboard non tactical ADP program 4 Shipboard nuclear active program
19. 2 6 erasable programmable read only memory EPROM 2 8 magnetic core storage 2 5 programmable read only memory PROM 2 8 random access memory RAM 2 8 read only memory ROM 2 7 semiconductor storage 2 6 Storage secondary 2 9 to 2 18 data organization 4 10 to 4 15 magnetic disk 2 9 to 2 12 magnetic drum 2 16 to 2 18 magnetic tape 2 13 to 2 16 Symbolic languages 3 7 Synchronous transmission 4 18 System commands 3 3 System flowcharts 3 11 T Tape magnetic 2 13 to 2 16 Tape recording density 2 14 Testing 3 21 Transfer instructions 2 3 Transistors 1 10 U Uses of a digital computer 1 14 to 1 17 Utility programs 3 4 to 3 6 report program generators 3 5 to 3 6 sort merge programs 3 4 to 3 5 V Vacuum tube 1 10 Variable word length computers 4 12 Very large scale integration VLSI 2 6 Volatile memory 2 6 Ww Wide area networks 4 17 Word 4 14 Word oriented addressable computers 4 11 INDEX 5 Word processing software 3 23 to 3 24 Work center uses SNAP II 1 15 INDEX 6 Assignment Questions Information The text pages that you are to study are provided at the beginning of the assignment questions 1 1 1 3 1 4 1 5 ASSIGNMENT 1 Textbook assignment Chapter 1 Operational Concepts pages 1 1 through 1 25 When was the first mechanical adding 1 6 Mechanical computers are what type of machine invented devices 1 1264 1 Digital
20. 20 You will have to have specific information about the computer you are to use It will tell you how the language is implemented on that particular computer in order to code a program The computer manufacturers or software designer will provide these specifics in their user s manual Get a copy of the user s manual and study it before you begin to code The differences may seem minor to you but they may prevent your program from running Once coding is completed the program must be debugged and tested before implementation Debugging Errors caused by faulty logic and coding mistakes are referred to as bugs Finding and correcting these mistakes and errors that prevent the program from running and producing correct output is called debugging Rarely do complex programs run to completion on the first attempt Often time spent debugging and testing equals or exceeds the time spent in program coding This is particularly true if insufficient time was spent on program definition and logic development Some common mistakes which cause program bugs are mistakes in coding punctuation incorrect operation codes transposed characters keying errors and failure to provide a sequence of instructions a program path needed to process certain conditions To reduce the number of errors you will want to carefully check the coding sheets before they are keyed into the computer This process is known as desk checking and should include an examination
21. MEDIUM The material on which data and instructions are recorded such as punched cards paper tape and all forms of magnetic media tape disk drum and so on MEMORY A device or section of the computer in which computer instructions and data can be stored for retrieval synonymous with primary or internal storage MICROCOMPUTERS The smallest category of computers usually with the entire central processing unit on a single chip Unlike large scale and minicomputer systems they are designed to be used by one person at a time hence the term personal computer PC MICROPROCESSOR The semiconductor central processing unit cpu of a microcomputer that fits on a small silicon chip The microprocessor is the central chip containing the control units of the computer MICROSECOND One millionth of a second MILLISECOND One thousandth of a second MINICOMPUTERS Midsize computers that are smaller than large scale systems but with the same components They are less expensive and have less strict environmental requirements MODEM Acronym for MOdulator DEModulator A device that converts data from digital to analog format for transmission on analog transmission lines and converts data in analog format to digital format for computer processing AI 6 MULTIPROCESSING A computer processing mode that provides for simultaneous processing of two or more programs or routines by use of multiple cpu s MULTIPROGRAMMING
22. OUTPUT DEVICES EXTERNAL Input and output devices are similar in operation but perform opposite functions It is through the use of these devices that the computer is able to communicate with the outside world Input data may be in any one of three forms 1 Manual inputs from a keyboard or console 2 Analog inputs from instruments or sensors 3 Inputs from a source on or in which data has previously been stored in a form intelligible to the computer Computers can process hundreds of thousands of computer words or characters per second Thus a study of the first method manual input reflects the inability of human operated keyboards or keypunches to supply data at a speed that matches the speed of digital computers A high average speed for keyboard operation is two or three characters per second that when coded to form computer words would reduce the data input rate to the computer to less than a computer word per second Since mainframe computers are capable of reading several thousand times this amount of information per second it is clear that manual inputs should be minimized to make more efficient use of computer time However as a rule the keyboard is the normal input media for microcomputers Input data that has previously been recorded on paper tapes magnetic tapes magnetic disks or floppy disks in a form understood by the program may also be entered into the computer These are much faster methods than entering data manually
23. PROTECTION HEADS PLATE Figure 2 21 Multiple access arms read write heads used with disk packs FLOPPY DISK DRIVE UNITS INPUT OUTPUT Floppy disk drive units are physically smaller than magnetic disk drive units and are typically used with personal desktop computers fig 2 22 The unit consists of a disk drive in which the disk rotates and a controller containing the electronic circuitry that feeds signals onto and from the disk The disk diskette is a thin flexible platter floppy disk coated with magnetic material so characters can be recorded on the surface in the form of magnetized spots Floppy disks come in several sizes from 3 to 8 inches in diameter The most common are the 8 inch disk the 5 1 4 inch disk and the 3 1 2 inch disk 2 23 CRT SPLAY SCREEN FLOPPY DISK DRIVE DOOR DISK LOAD SLOT LED DISK ACCESS INDICATOR LABEL Figure 2 22 Floppy disk drive unit PRINTERS OUTPUT Printers are widely used output devices that express coded characters on hard paper document copy fig 2 23 They print out computer program results as numbers letters words symbols graphics or drawings Printers range from electronic typewriters to high speed printers High speed printers are usually used on mainframes and minis to prepare supply requisitions pay checks inventory or financial reports at 10 lines per second and faster The types of printers we ll discuss are daisy wheel dot matrix ink jet and laser
24. Procedure oriented languages were developed to allow a programmer to work in a language that is close to English or mathematical notation This improves overall efficiency and simplifies the communications process between the programmer and the computer These languages have allowed us to be more concerned with the problems to be solved rather than with the details of computer operation For example COBOL COmmon Business Oriented Language was developed for business applications It uses statements of everyday English and is good for handling large data files FORTRAN FORmula TRANslator was developed for mathematical work It is used by engineers scientists statisticians and others where mathematical operations are most important BASIC Beginner s All Purpose Symbolic Instruction Code was designed as a teaching language to help beginning programmers write programs Therefore it is a general purpose introductory language that is fairly easy to learn and to use With the increase in the use of microcomputers BASIC has regained popularity and is available on most microcomputer systems Other languages gaining in popularity are PASCAL and Ada PASCAL is being used by many colleges and universities to teach programming because it is fairly easy to learn yet is a more powerful language than BASIC Although PASCAL is not yet a standardized language it is still used rather extensively on microcomputers It has greater programming capabilities on
25. Software Word processing Correcting errors For manuscript writing memorandum writing identification card application filing and recordkeeping Six Shipboard Non tactical ADP Program To support shipboard and intermediate level maintenance supply financial and administrative functions Operating instructions are written in everyday English Unauthorized entry into the main computer s program Dependent on a work center s need COSAL APL EIC SHIP S FORCE WORK LIST and CSMP Unclassified Operating system To load an external operating system into the computer s internal memory The computer is reading a properly inserted floppy disk but it does not have an operating system on it 1 24 4 54 4 55 4 56 4 57 4 58 4 59 4 60 The program name No more than ten Destroy some or all of it 10 to 50 degrees Celsius or 50 to 120 degrees Fahrenheit Backup files Use a floppy disk and the diskcopy procedure Magnetic tape 1 25 CHAPTER 2 HARDWARE LEARNING OBJECTIVES Upon completion of this chapter you will be able to do the following 1 Explain the cpu and describe the functions of the different sections 2 Categorize the types of storage and their functions 3 Describe how storage is classified 4 Analyze and compare the input output devices and explain their functions INTRODUCTION Components or tools of a computer system are grouped into one of two categories hardware or sof
26. Word processing 4 Graphics The tiny doughnut shaped rings used to make up magnetic core storage are made of what material 1 Aluminum 2 Steel 3 Tin 4 Ferrite Data is stored in computers in what form 1 Binary 2 Decimal 3 Octal 4 Hexadecimal The state of each core in magnetic core storage is changed by what The amount of magnetism The amount of current The direction of magnetism The direction of current TES 2 16 2 17 2 18 2 19 2 20 2 21 Electronic circuits are placed on a silicon chip by what method 1 Wired 2 Drawn 3 Etched 4 Printed Each of the individual electronic circuits on a silicon chip is called what 1 A memory cell 2 A bit cell 3 byte cell 4 A holding cell Semiconductor storage has which of the following drawbacks 1 Itis too slow 2 Itis expensive 3 It is volatile 4 It is unreliable Using a very thin crystal made of semiconductor material what type of memory can be created 1 Bubble 2 Magnetic core 3 Semiconductor 4 Capacitive In bubble memory where is the control circuit imprinted on the crystal of semiconductor material 1 The side 2 The bottom 3 The middle 4 The top Who installs the programs in read only memory The programmer The manufacturer The operator The dealer Bes 2 22 2 23 2 24 2 25 2 26 2 27 Programs that are tailored to certain needs and permanently in
27. a control circuit imprinted on top of the crystal In this manner data can be stored by changing the polarity of the magnetic domains Since the principle is the same as for magnetic core storage bubble memory is considered nonvolatile The data is retained even if there is a power failure Furthermore the process of reading from bubble memory is nondestructive meaning that the data is still present after being read This is not the case with core storage which must be regenerated after being read If we were to view these magnetic domains under a microscope they would look like tiny bubbles hence the name bubble memory 2 6 SEMICONDUCTOR ORTHOFERRITE MATERIAL MAGNETIC BUBBLE NATURAL DOMAIN PATTERN Figure 2 5 Bubble memory Q 9 Magnetic core storage is made up of what Q 10 A semiconductor memory consists of what Q 11 What is another name for semiconductor memory chips Q 12 In computer storage what does volatile mean Q 13 What type of storage can retain its data even if there is a power failure or breakdown Q 14 Bubble memory consists of what Q 15 How are the magnetic domains of a bubble memory switched Q 16 What do we mean when we say that reading from bubble memory is nondestructive CLASSIFICATIONS OF INTERNAL STORAGE Up to this point you have learned some of the general functions of the cpu the physical characteristics of memory and how data is stored in the internal storage section Now w
28. a fraction of their office machine counterparts and could be run on general purpose microcomputers This was unique because general purpose microcomputers could be used for functions such as spreadsheets data base management systems and programming in common computer languages The Navy saw the obvious uses to which microcomputers using the word processing programs could be put Some of these are manuscript writing memorandum writing identification card application filing and recordkeeping 1 14 ACCOUNTING AND RECORDKEEPING There are virtually unlimited applications for the computer in today s modern business world from basic accounting functions to controlling the manufacture of products and of course keeping records of these actions Six standard systems dealing with accounting applications are widely accepted These systems are 1 order entry 2 inventory control 3 accounts receivable 4 accounts payable 5 general ledger and 6 payroll Figure 1 10 shows a simplified flowchart of payroll The area of recordkeeping has two requirements legal and audit The Navy has included similar functions in its Shipboard Non Tactical ADP Program for work center use INPUT EMPLOYEE HOURS PAY RATE COMPUTE OVERTIME PAY COMPUTE REGULAR PAY PRINT PAYCHECK Figure 1 10 Programming flowchart used to build a payroll program WORK CENTER USES SNAP II Every Navy rating has the responsibi
29. along the length of the tape How are these tracks referenced to each other 1 Perpendicular 2 Parallel 3 Vertical 4 Random 2 59 How does a two gap head allow for increased speed 1 By checking before writing 2 By using two gaps to write 3 By checking while writing 4 By using two gaps to check 2 60 What are the most common tape densities in bits bytes per inch 1 500 and 1 000 bpi 2 600 and 1 200 bpi 3 700 and 1 500 bpi 4 800 and 1 600 bpi The drive motor of a disk drive unit rotates the disk at a constant speed 2 61 normally how many revolutions per minute 1 2 000 rpm 2 2 500 rpm 3 3 000 rpm 4 3 600 rpm 2 62 The usual range of rotational speed for floppy disks is what 1 100 to 200 rpm 2 200 to 300 rpm 3 300 to 400 rpm 4 400 to 500 rpm 12 The distance between the read write head and the surface of a hard disk is called what 1 The flying height 2 The disk height 3 The head height 4 The recording height Floppy disks come in several sizes with diameters of what size range 2 to 6 inches 3 to 8 inches 4to 9 inches 5 to 10 inches In the character at a time impact printer class which printer has the most professional looking pleasing to the eye print 1 Dot matrix 2 Inkjet 3 Daisy wheel 4 Laser What is another name for the dot matrix printer Hammer matrix 2 Pin matrix 3 Ink matrix 4 Wire matrix Dot matrix printers have which of the
30. and baseband A party line Global connections It is an acronym for modulator demodulator Those devices that serve to interconnect 4 21 4 39 It is given a signal warning that data is about to be transmitted 4 40 Handshaking 4 22 APPENDIX I GLOSSARY ACCESS TIME The amount of time between the time a request for data from a storage device is made and the time the data is delivered ADA A high level programming language designed by the Department of Defense ALPHAMERIC ALPHANUMERIC CHARACTER SET The set of characters that includes letters numbers and special characters ANALOG COMPUTER A computer that solves problems using continuous data from physical quantities like voltage or temperature APPLICATION PROGRAMS SOFTWARE Programs written to solve user problems ARITHMETIC LOGIC UNIT The part of the cpu that contains the logic capability and performs all the arithmetic functions addition subtraction multiplication and division ARTIFICIAL INTELLIGENCE The capability of a machine to perform human like intelligence functions such as learning adapting reasoning and self correction ASCII American Standard Code for Information Interchange A standardized 8 bit code originally a 7 bit code designed for transmitting and processing data ASSEMBLER A computer program that translates source programs written in assembly language into machine language object programs ASSEMBLY LANGUAGE
31. and efficiency Special purpose Continuous electrical or physical conditions Mechanical or electromechanical Hybrid computers Business and scientific data processing Digital computers deal with discrete quantities while analog computers deal with continuous physical variables By the accuracy with which physical quantities can be sensed and displayed Third The number of significant figures carried in the computations Design of the computer processing unit General purpose digital computer Generations Significant change in computer design The vacuum tube They were unreliable required a lot of power to run and produced so much heat that air conditioning was needed to protect computer parts 1 23 A 27 A 28 4 29 4 30 4 31 4 32 4 33 4 34 4 35 4 36 4 37 4 38 4 39 4 40 4 41 4 42 4 43 4 44 4 45 4 46 4 47 4 48 4 49 4 50 4 51 4 52 4 53 Thousandths of a second millisecond Unsophisticated and machine oriented By the use of small long lasting transistors With the introduction of magnetic disk storage and the use of core for main storage Symbolic machine languages or assembly languages Faster internal processing speeds Faster execution of instructions Over 100 million Both scientific and business data processing applications Microcomputers and minicomputers Read only memory How to properly and effectively use the computing power available
32. bit code developed to standardize a binary code to give the computer user the capability of using several machines to process data regardless of the manufacturer A PARITY CHECK BIT is used to detect errors in computer circuitry MAGNETIC CORE STORAGE is used as primary storage in some computers 4 19 PRIMARY STORAGE CAPACITY AND ADDRESSES are designed and built into the computer by the manufacturer Computers may be WORD ADDRESSABLE CHARACTER ADDRESSABLE or FLEXIBLE Data in SECONDARY STORAGE like disk or tape is normally organized by bits characters bytes fields records and files STORAGE ACCESS METHODS vary with the types of media and devices you are using SEQUENTIAL ACCESS STORAGE is associated with punched cards paper tape and magnetic tape DIRECT ACCESS STORAGE is obtained by using magnetic disks and drums RANDOM ACCESS STORAGE refers to magnetic core semiconductor thin film and bubble storage A NETWORK is any system composed of one or more computers and terminals however most are composed of multiple terminals and computers LOCAL AREA NETWORKS LANs allow dissimilar machines to exchange information within one universal system within a building or small geographic area WIDE AREA NETWORKS provide for global connections and are sometimes referred to as global networks A MODEM converts the digital signal produced by your terminal or the computer to an audio signal suitable for transmission over a
33. cpu or mainframe The central processing unit IS THE COMPUTER It is the cpu that processes the data transferred to it from one of the various input devices and then transfers either the intermediate or final results of the processing to one of many output devices A central control section and work areas are required to perform calculations or manipulate data The cpu is the computing center of the system It consists of a control section internal storage section main or primary memory and arithmetic logic section fig 2 1 Each of the sections within the cpu serves a specific function and has a particular relationship to the other sections within the cpu 2 1 INPUT OUTPUT OUTPUT STORAGE PROGRAM STORAGE STORAGE AREA WORKING STORAGE AREA wer ARITHMETIC LOGIC SECTION PUNCHED PUNCHED CARD CARD CENTRAL PROCESSING UNIT Ce esdas eee CONTROLSECTION INTERNAL STORAGE SECTION PAPER PAPER TAPE TAPE CONSOLE TYPEWRITER CONSOLE KEYBOARD MAGNETIC CHECKS PRINTED REPORTS gt DATA FLOW DISK DISK OR fe gt OR DRUM INSTRUCTION FLOW DRUM gt FLOW OF CONTROL Figure 2 1 Functional units of a computer system CONTROL SECTION The control section may be compared to a telephone exchange because it uses the instructions contained in the program i
34. data from one storage location to another and to rearrange and change data elements in some prescribed manner what type of instructions are used Input output Data movement Transfer of control Conditional logic dus Transfer of control instructions are classified as which of the following types 1 Conditional only 2 Unconditional only 3 Conditional and unconditional 4 Conditional and distributed Errors caused by faulty logic and coding mistakes are referred to as what 1 Mistakes 2 Errors 3 Faults 4 Bugs 3 53 3 54 3 55 3 56 The process of carefully checking the coding sheets before they are keyed into the computer is known as what Desk checking Code checking Program checking Computer checking A vapor A definition of the problem a description of the system a description of the program and operator instructions make up what package 1 Training 2 Security 3 Orientation 4 Documentation Which of the following is another name for packaged software 1 Rented programs 2 Manufactured programs 3 Off the shelf programs 4 On the shelf programs Under the word processing software control you generally enter the text using what method 1 Tape 2 Disk 3 Drum 4 Keyboard QUESTION 3 57 IS TO BE JUDGED TRUE OR FALSE 3 57 Spelling checker software helps find 20 misspelled words not misused words 1 True 2 False 3 58 What type of software
35. devices 2 28 to 2 33 flat panel displays 2 31 to 2 32 raster scan crts 2 28 to 2 31 floppy disk drive units input output 2 23 keyboards input 2 27 to 2 28 magnetic disk drive units input output 2 22 to 2 23 magnetic tape units input output 2 19 to 2 22 printers output 2 24 to 2 27 daisy wheel printers 2 25 dot matrix printers 2 25 INDEX 2 Hardware Continued ink jet printers 2 27 laser printers 2 27 internal storage types of 2 4 to 2 7 bubble storage 2 6 magnetic core storage 2 5 semiconductor storage the silicon chip 2 6 secondary storage 2 9 to 2 18 magnetic disk 2 9 to 2 12 magnetic drum 2 16 to 2 18 magnetic tape 2 13 to 2 16 Hard wired memory 2 7 History 1 2 to 1 3 I Ink jet printers 2 27 Input output devices external 2 18 to 2 33 display devices 2 28 to 2 33 floppy disk drive units input output 2 23 keyboards input 2 27 to 2 28 magnetic disk drive units input output 2 22 to 2 23 magnetic tape units input output 2 19 to 2 22 printers output 2 24 to 2 27 Instructions arithmetic 2 3 Instructions control 2 3 Instructions logic 2 3 Instructions transfer 2 3 Integrated circuits ICs 2 6 Internal storage types of 2 4 to 2 7 bubble storage 2 6 magnetic core storage 2 5 semiconductor storage the silicon chip 2 6 Interrecord interblock gap 2 16 K Keyboards input 2 27 to 2 28 L Large scale integration LSI 2 6 Laser printers 2 2
36. disks and punched cards STORED PROGRAM Tphe set of instructions stored in computer memory for execution SUBROUTINE LIBRARY A set of standard and proven computer routines that are kept on file for use at any time TELECOMMUNICATIONS The transmission of data between computer systems and or terminals in different locations TELEPROCESSING A method of data processing in which communication devices are used TERMINAL A device linked to the central processor for entering or receiving data and programs TIME SHARING A processing mode in which many users share the computer systems resources through online terminals Each user gets a slice of computer time TRACK 1 One of seven or nine horizontal rows stretching the entire length of a magnetic tape and on which data can be recorded 2 One of a series of concentric circles on the surface of a disk 3 One of a series of circular bands on a drum UNBLOCKED Having a blocking factor of one logical record per block USER PROGRAMS Programs written to solve specific user problems called applications software USERS 1 The people who use the output from computer processing 2 The people who operate a computer for their own purposes UTILITY PROGRAMS UTILITIES Programs designed to perform often needed general functions WIDE AREA NETWORK A network that usually covers large geographical areas Communications between stations or terminals usually occur using
37. first or second generation equipment Because the miniature components are more reliable maintenance is reduced New mass storage such as the data cell was introduced during this generation giving a storage capacity of over 100 million characters Drum and disk capacities and speed have been increased the portable disk pack has been developed and faster higher density magnetic tapes have come into use Considerable improvements were made to card readers and printers while the overall cost has been greatly reduced Applications using online processing real time processing time sharing multiprogramming multiprocessing and teleprocessing have become widely accepted More on this in later chapters Pr NONO UgR ae PERRA IU Ji c ne p ad ARR RA n EET saan cem TE TIT PERT T d Figure 1 8 Third generation computers used microcircuits Manufacturers of third generation computers are producing a series of similar and compatible computers This allows programs written for one computer model to run on most larger models of the same series Most third generation systems are designed to handle both scientific and business data processing applications Improved program and operating software has been designed to provide better control resulting in faster processing These enhancements are of significant importance to the computer operator They simplify system initialization booting and minimize the need for inputs to
38. for transmission This converted data is then transmitted over the telephone or land lines to another modem that is located near the main computer system s cpu The data now in digital form can be sent directly to the cpu for processing The same route 1s followed when information is sent from the cpu back to the remote terminal DIGITAL IMPULSES DIGITAL IMPULSES REPRESENTING O AND 1 BITS OF DATA ANALOG SIGNAL FOR VOICE COMMUNICATION NETWORK FRONT END CPU PROCESSOR MAINFRAME MINICOMP COMPUTER INTERFACE BETWEEN THE REMOTE USER AND DATA TRANSMISSION CHANNELS INTERFACE BETWEEN DATA TRANSMISSIONS CHANNELS AND THE CPU Figure 4 14 Modems used in network system Data communications and networks expand our use of computer technology by providing a means for computers and other machines to talk to each other 4 18 Q 30 Any system composed of one or more computers and terminals can be defined as what 31 A network system allows dissimilar machines to do what within one universal system Q 32 What does the make up of a local area network consist of Q 33 How many designs of local area networks are there that can be used Q 34 What are the different designs of local area networks called Q 35 What is a baseband communication channel like Q 36 What do wide area networks provide for Q 37 Where does the word modem come from Q 38 What are interface elements Q 39 How does
39. gt 40 COMPUTE REGULAR PAY COMPUTE OVERTIME PAY PRINT PAYCHECK Tools of Flowcharting Next we will take a look at the tools used in flowcharting These tools are the fandamental symbols graphic symbols flowcharting template and the flowcharting worksheet FUNDAMENTAL SYMBOLS To construct a flowchart you must know the symbols and their related meanings They are standard for the military as directed by Department of the Navy Automated Data Systems Documentation Standards SECNAVINST 5233 Symbols are used to represent functions These fundamental functions are processing decision input output terminal flow lines and connector symbol All flowcharts may be initially constructed using only these fundamental symbols as a rough outline to work from Each symbol corresponds to one of the functions of a computer and specifies the instruction s to be performed by the computer The contents of these symbols are called statements Samples of these fundamental symbols definitions examples and explanations of their uses are shown in figure 3 3 3 12 DEFINITION PROCESS SYMBOL is used to represent general processing func tions not represented by other symbols It depicts the process of operations resulting in a change of value form or location of information INPUT OUTPUT SYMBOL is used to represent any function of an I O device Making informa tion available for processing is an Input function reco
40. measured in millionths of a second microseconds Like the first generation a particular computer of the second generation was designed to process either scientific or business oriented problems but not both The software was also improved Symbolic machine languages or assembly languages were used instead of actual machine languages This allowed the programmer to use mnemonic operation codes for instruction operations and symbolic names for storage locations or stored variables Compiler languages were also developed for the second generation computers see chapter 3 M 2 Ns Figure 1 7 Second generation computers used transistors THIRD GENERATION The computers of this generation 1964 1970 many of which are still in use are characterized by miniaturized circuits This reduces the physical size of computers even more and increases their durability and internal processing speeds One design employs solid state logic microcircuits fig 1 8 for which conductors resistors diodes and transistors have been miniaturized and combined on half inch ceramic squares Another smaller design uses silicon wafers on which the circuit and its components are etched The smaller circuits allow for faster internal processing speeds resulting in faster execution of instructions Internal processing speeds are measured in billionths of a second nanoseconds The faster computers make it possible to run jobs that were considered impractical or impossible on
41. of information is connected to all input devices The entire system is usually housed within the same building or the same geographic area A local area network is made up of a communications facility for example a coaxial cable such as that used for cable television and interface units creating a link for the computers and terminals to the communications facility Two designs can be used broadband or baseband WORD ELECTRONIC DATA PBX VOICE PROCES SING FILING TERMINALS DATA LOCAL AREA NETWORK MINICOMPUTERS OUTPUT MICROCOMPUTERS MAINFRAME DEVICE COMPUTER Figure 4 12 Local area network system A baseband communications channel uses the basic frequency band of radio waves and a coaxial cable This coaxial cable has one channel which is like a party line Only two machines can use this cable 4 16 at one time even though many have the channel available but there is no central switching unit to route traffic over the network A more expensive channel called a broadband communications channel can handle more advanced applications This includes transmission of voice as well as data and text Because of the use ofa controller to route traffic for a large number of simultaneous users the users are able to share one of the many individual channels of the system WIDE AREA NETWORKS Wide area networks provide for global connections and are sometimes referred to as global networks Organizations are able to send infor
42. of tape BOT and where it ends known as the end of tape EOT The length of tape between the BOT and EOT is referred to as the usable recording reading writing surface or usable storage area BOT EOT markers are usually made of short silver strips of reflective tape 1 4 inch wide by 1 2 inch long as shown in figure 2 14 The BOT marker is normally placed toward the front edge of the tape the side nearest you when the tape is mounted on the tape unit The EOT marker is placed toward the back edge the side farthest from you when the tape is mounted on the tape unit They are placed approximately 15 to 20 feet in from each end on the shiny side of the tape Sometimes holes or clear plastic inserts are used as markers in place of reflective strips Regardless of the method used the BOT EOT markers are sensed by an arrangement of lamps and or photodiode sensors to indicate where reading and writing is to begin and end REFLECTIVE MARKER USABLE READING WRITING SURFACE REFLECTIVE MARKER Figure 2 14 Beginning of tape BOT and end of tape EOT markers We can make records on magnetic tape any size we need to hold the data We are restricted only by the length of the tape or the capacity of internal storage For example a record can be one character several characters or thousands of characters in length The collection of records is called a file A file containing payroll records is called a payroll file a fil
43. one place to another and to print hard copies of a document These are but a few of the functions allowed however as you become more familiar with computers you will learn them all The cursor control key allows you to move to different locations on the screen The design of keyboards varies from device to device and is dependent on the requirements of the system in which the keyboards are installed Keyboards are generally used with nontactical computer systems However the newer tactical display system consoles have optional keyboards for data entry A keyboard may be built into the display device or it may be a separate component connected only by a communication cable DISPLAY DEVICES Display devices are the crts and other displays that are part of computer terminals computer consoles and microcomputers They are designed to project show exhibit or display softcopy information alphanumerics or graphic symbology The information displayed on a display device screen is not permanent That is where the term soft copy comes from The information is available for viewing only as long as it is on the display screen Two types of display devices used with personal microcomputers are the raster scan crt s and the flat panel displays Raster Scan Crts Raster scan crts tv scan video monitors or display monitors are used extensively in the display of alphanumeric data and graphics They are used primarily in nontactical display applica
44. reading at any point This is like the phonograph record you can place the needle at any point and begin playing at any point Figure 2 20 Magnetic disk drive unit Located within each disk drive unit is a drive motor that rotates the disk at a constant speed normally 3 600 revolutions per minute rpm or if you prefer 60 revolutions per second The rotational speed for floppy disks is usually between 300 and 400 rpm because of their plastic base Data is written on the tracks of a spinning disk surface and read from the surface by one or more multiple read write heads When reading from and writing to hard disks rigid disks the read write heads float on a cushion of air and do not actually touch the surface of the disk The distance between the head and the surface varies from a millionth of an inch to one half millionth of an inch This distance is called the flying height When multiple disks platters are packaged together as a unit in a disk pack a number of access arms and read write heads are used to access both surfaces of each platter fig 2 21 The disk pack shown consists of six metal disks mounted on a central spindle Data can be recorded on all surfaces except the top surface of the top disk and the bottom surface of the bottom disk These two surfaces are intentionally left blank for protection 2 22 DIRECTION OF ROTATION TOP PROTECTION PLATE ACCESS ARM MOVEMENT ONE OF TEN BOTTOM READ WRITE
45. relative humidity of 1096 to 80 X RAYS There is some question about the effect that airport x ray machines have on disks It has been the normal experience that the walk through x ray machines at airports have no effect on floppy disks however this is not to say there will be no effect It is up to you because these disks contain the data you work with and need You may not want to take the chance the disks will be affected Labeling When labeling the outside of a floppy disk write the label before attaching it to the disk Never use a pencil or ballpoint pen to write on a label once that label has been attached to a disk When you use an instrument with a sharp point to write on the label you can actually etch into the surface of the disk underneath the protective sheath thereby destroying that disk If you must write on a label once it has been attached to a disk use a felt tip marker Data Backup In virtually all computer systems the possibility exists for errors to occur that accidentally alter or destroy the data stored in the data bases or files This may occur because of natural disasters such as fire flood or power outages It may occur through operator error It may occur through equipment malfunction It is essential therefore to provide a means to ensure that any data lost can be recovered The most common method is backup files A backup file is merely a copy of a file If for some reason the file or data base is de
46. small computers than are possible with BASIC Ada s development was initiated by the U S Department of Defense DOD Ada is a modern general purpose language designed with the professional programmer in mind and has many unique features to aid in the implementation of large scale applications and real time systems Because Ada is so strongly supported by the DOD and other advocates it will become an important language like those previously mentioned Its primary disadvantage relates to its size and complexity which will require considerable adjustment on the part of most programmers The most familiar of the procedure oriented languages are BASIC and FORTRAN for scientific or mathematical problems and COBOL for file processing Programs written in procedure oriented languages unlike those in symbolic languages may be used with a number of different computer makes and models This feature greatly reduces reprogramming expenses when changing from one computer system to another Other advantages to procedure oriented languages are 1 they are easier to learn than symbolic languages 2 they require less time to write 3 they provide better documentation and 4 they are easier to maintain However there are some disadvantages of procedure oriented languages They require more space in memory and they process data at a slower rate than symbolic languages 11 With early computers the programmer had to translate instructions into what ty
47. standard telephone lines or microwave relays WORD COMPUTER A group of related bytes treated as a single addressable unit or entity in computer memory AI 9 APPENDIX II REFERENCE LIST Casady Mona J and Sandburg Dorothy C Word Information Processing South Western Publishing Co Cincinnati Ohio 1985 Davis Gordon B ntroduction to Electronic Computers McGraw Hill Book Co New York N Y 1971 Delco Electronics Fundamentals of Digital Computers Course General Motors Corp Milwaukee Wis 1972 Fuori William M D Arco Anthony M S and Ovilia Lawrence Introduction To Computer Operations 2nd edition Prentice Hall Inc Englewood Cliffs N J 1981 Jansen John T How Microprocessors Function Dun Donnelley Publishing Corp New York N Y 1983 Lavin Albert J III DSCS SW Data Systems Technician 3 amp 2 Volume 2 NAVEDTRA 10231 NETPDTC Pensacola Fla 1987 McGee Fred H III DPC Introduction to Programming in BASIC NAVEDTRA 10079 2 NETPDTC Pensacola Fla 1983 Mims Forrest M IIL Understanding Digital Computers Tandy Corp Co Fort Worth Tex 2nd edition 1987 Moore Alvin W et al Microprocessor Applications Manual McGraw Hill Book Co New York N Y 1975 Rau Bernie ZENITH 100 Series Microcomputer Operations NAVEDTRA 40801 Naval Oceanography Command Facility Bay St Louis Miss 1985 Shelly Gary B and Thomas J Cashman Introduction To Computer
48. tell the sort program what fields to sort on and whether to sort in ascending or descending sequence Let s examine two types of utility programs to give you some idea of how a utility program works The first will be sort merge and the second the report program generator RPG SORT MERGE PROGRAMS Sorting is the term given to arranging data records in a predefined sequence or order Merging is the combining of two or more ordered files into one file For example we normally think of putting a list of people s names in alphabetical order arranging them in sequence by last name We arrange those with the same last name in order by first name If we do this ourselves we know the alphabetic sequence B comes after A C after B and so on and it is easy to arrange the list even if it is a time consuming job On a computer the sequence of characters is also defined It is called the collating sequence Every coding system has a collating sequence The capability of a computer to compare two values and determine which is greater B is greater than A C is greater than B and so on makes sorting possible What about numbers and special 34 characters They are also part of the collating sequence In EBCDIC EBCDIC is a computer code that is discussed in detail in chapter 4 special characters such as amp and come in front of the alphabetic characters and numbers follow When you sort records in the defined sequence they are in asc
49. the recording surface is wasted 4 Too much of the recording surface is used The magnetic drum is another example of what type of access storage device 1 Random 2 Direct 3 Multiple 4 Single What is the speed range of a magnetic drum 1 300 to 3 000 rpm 2 400 to 4 000 rpm 3 500 to 5 000 rpm 4 600 to 6 000 rpm When using a magnetic drum what is rotational delay 1 Time that occurs in coming up to speed 2 Time that occurs in slowing down 3 Time that occurs in reaching a desired record location 4 Time that occurs in changing a drum 2 48 2 49 2 50 2 51 2 52 11 What is the storage capacity range of magnetic drums in characters or bytes of data 1 From 20 million to more than 150 000 million 2 From 30 million to more than 150 000 million 3 From 40 million to more than 200 000 million 4 From 50 million to more than 200 000 million Input data may be in any one of how many forms 1 Five 2 Two 3 Three 4 Four When data is input from a keyboard a high average speed is how many characters per second One to two Two to three Three to four Four to five Hob Output information is made available in how many forms 1 One 2 Two 3 Three 4 Four Magnetic tape stores data in what manner 1 Sequential 2 Non sequential 3 Direct 4 Random 2 53 2 54 2 55 2 57 The magnetic tape unit reads and writes 2 58 data in channels or tracks
50. used to branch or change the sequence of program control depending on the outcome of the comparison If the outcome of a comparison is true control is transferred to a specific statement number If it proves false processing continues sequentially through the program Unconditional transfer of control instructions are used to change the sequence of program control to a specified program statement regardless of any condition Coding a Program Regardless of the language used there are strict rules the programmer must adhere to with regard to punctuation and statement structure when coding any program Using the programming flowchart introduced earlier we have now added a program coded in BASIC to show the relationship of the flowchart to the actual coded instructions fig 3 7 Don t worry about complete understanding just look at the instructions with the flowchart to get an idea of what coded instructions look like 3 19 CALCULATE MONTHLY INTEREST RATE COMPUTE COMPUTE AMOUNT APPLIED TO INTEREST COMPUTE AMOUNT APPLIED TO PRINCIPAL COMPUTE LOAN BALANCE PRINT MONTHLY SUMMARY 10 PRINT ENTER MONTHLY PAYMENT 20 PRINT LOAN AMOUNT INTEREST RATE 30 INPUT D B I 40 LET R 1 12 50 FOR M 1 TO 36 60 LETA B R 70 LET P D A 80 LET B B P 90 PRINT M D B P A 100 NEXT M 110 PRINT WITH ONE FINAL PAYMENT OF B 120 END Figure 3 7 Programming flowchart and coded program 3
51. you will receive retirement points if you are authorized to receive them under current directives governing retirement of Naval Reserve personnel For Naval Reserve retirement this course is evaluated at 4 points Refer to Administrative Procedures for Naval Reservists on Inactive Duty BUPERSINST 1001 39 for more information about retirement points Student Comments NEETS Module 22 Course Title Introduction to Digital Computers NAVEDTRA 14194 Date We need some information about you Rate Rank and Name SSN Command Unit Street Address City State FPO Zip Your comments suggestions etc Privacy Act Statement Under authority of Title 5 USC 301 information regarding your military status is requested in processing your comments and in preparing a reply This information will not be divulged without written authorization to anyone other than those within DOD for official use in determining performance NETPDTC 1550 41 Rev 4 00 1X CHAPTER 1 OPERATIONAL CONCEPTS LEARNING OBJECTIVES Learning objectives are stated at the beginning of each chapter These learning objectives serve as a preview of the information you are expected to learn in the chapter The comprehensive check questions placed throughout the chapters are based on the objectives By successfully completing the Nonresident Training Course NRTC you indicate that you have met the objectives and have learned the infor
52. your terminal If this conversion were not carried out the digital signal would degenerate during transmission and become garbled oO 0 00 00 O O HG AA CD OH RD SD TR MR Figure 4 13 Modem The physical link or medium that is used to carry or transmit data from one location to another is a communications channel It allows remotely located input output devices to communicate directly with the computer s central processing unit cpu Telephone lines often referred to as land lines are a frequently used type of communications channel In a simple data communications system terminals and other remote I O devices are linked directly to one or more cpu s to allow users to enter data and programs and receive output information Interface elements those devices that serve to interconnect such as modems are used to bridge and control the 4 17 different data communications environments Modems are used to permit the system to switch back and forth from computer digital data to analog signals that can be transmitted over communications lines A modem never knows exactly when to expect data therefore it must be given some type of signal warning that data is about to be transmitted This gives the modem time to get itself aligned and in synchronization with the incoming signal Special characters known as message characters provide this warning and are placed in front of and behind the data to mark the beginning and ending of the mess
53. 05 Figure 2 2 Memory locations MAGNETIC CORE STORAGE Although magnetic core storage is no longer as popular as it once was we will cover it in some detail because its concepts are easily understood and apply generally to the more integrated semiconductor and bubble type memories Magnetic core storage is made up of tiny doughnut shaped rings made of ferrite iron that are strung on a grid of very thin wires fig 2 3 Since data in computers is stored in binary form refer to NEETS module 13 a two state device is needed to represent the two binary digits bits 0 for off and 1 for on In core storage each ferrite ring can represent a 0 or bit depending on its magnetic state If magnetized in one direction it represents a 1 bit and if magnetized in the opposite direction it represents a 0 bit These cores are magnetized by sending an electric current through the wires on which the core is strung It is this direction of current that determines the state of each core 0 BIT OR OFF 1 BIT OR ON Figure 2 3 T wo state principle of magnetic storage 2 5 SEMICONDUCTOR STORAGE THE SILICON CHIP Semiconductor memory consists of hundreds of thousands of tiny electronic circuits etched on a silicon chip fig 2 4 Each of these electronic circuits is called a bit cell and can be in either an off or on state to represent a 0 or 1 bit depending on whether or not current is flowing in that cell Another name you will
54. 4 using a desktop computer 1 17 to 1 21 operating system 1 18 booting the system 1 18 running an application program 1 19 storage media handling and backup 1 19 data backup 1 21 exposure 1 20 handling 1 20 labeling 1 21 storage 1 20 P Packaged software 3 23 to 3 27 data management 3 24 to 3 25 graphics 3 26 to 3 27 spreadsheets 3 25 to 3 26 word processing 3 23 to 3 24 Parallel processing 3 22 Parity bit 4 7 Parity check 4 7 PASCAL 3 7 Password 1 16 Pels 2 29 Pixels 2 29 Printers output 2 24 to 2 27 daisy wheel printers 2 25 dot matrix printers 2 25 ink jet printers 2 27 laser printers 2 27 Procedure oriented languages 3 7 to 3 8 Programmable read only memory PROM 2 8 Programming 3 8 to 3 22 coding 3 18 to 3 22 debugging 3 21 documentation 3 21 to 3 22 flowcharting 3 11 to 3 18 implementation 3 22 overview of programming 3 9 to 3 11 testing 3 21 Programming languages 3 6 to 3 8 Ada 3 7 BASIC 3 7 COBOL 3 7 FORTRAN 3 7 machine languages 3 6 to 3 7 PASCAL 3 7 procedure oriented languages 3 7 to 3 8 symbolic languages 3 7 Prompt 1 19 Protocol 4 18 R Random access memory RAM 2 8 Raster scan crts 2 28 to 2 31 Read only memory ROM 2 7 Read write memory 2 8 Record 4 14 Record block 2 15 Recording density tape 2 14 Reference list AII l Report program generators 3 5 to 3 6 ROM read only memory 2 7 S Sector method 2 12 Semicon
55. 7 Loading 2 3 Local area networks LANs 4 16 to 4 17 Logic instructions 2 3 M Machine languages 3 6 to 3 7 Macroinstructions 3 7 Magnetic core storage 2 4 to 2 5 4 9 to 4 10 Magnetic disk drive units input output 2 22 to 2 23 Magnetic tape units input output 2 19 to 2 22 Mailing list programs 3 24 Memory bubble 2 6 Memory nondestructive 2 6 Memory read write 2 8 Memory see storage also Memory volatile 2 6 Miniaturized circuits 1 11 Mnemonic instruction codes 3 7 Modems 4 17 to 4 18 Multiprocessor shared resource systems 3 2 Multiuser multitasking operating systems 3 2 N Networks 4 16 to 4 19 local area networks LANs 4 16 to 4 17 wide area networks 4 17 Nondestructive memory 2 6 O Operating systems 1 18 3 1 to 3 4 Operational concepts 1 1 to 1 25 classification of computers 1 3 to 1 9 accuracy of computers 1 7 to 1 9 analog computers 1 6 digital computers 1 6 electromechanical computers 1 4 electronic computers 1 5 INDEX 3 Operational concepts Continued general purpose computers 1 6 mechanical computers 1 3 special purpose computers 1 6 digital computer generations 1 10 to 1 14 first generation 1 10 fourth generation and beyond 1 12 second generation 1 10 third generation 1 11 history of computers 1 2 to 1 3 uses of a digital computer 1 14 to 1 17 accounting and recordkeeping 1 15 work center uses SNAP 1 15 word processing 1 1
56. A computer processing mode that provides for overlapping or interleaving the execution of two or more programs at the same time by a single processor NANOSECOND A billionth of a second NETWORK Computers and terminals linked together through a communications system to allow users at different locations to share data files devices and programs ONLINE PROCESSING Processing from terminals under the direct control of a computer OPERATING SYSTEM Software that controls the execution of programs An operating system may provide services such as input output control and data management It may also provide job scheduling memory allocation and other general functions It is usually loaded by a bootstrap program OUTPUT The results of computer processing It may be data transferred to tape disk paper and so on PACKAGED SOFTWARE Programs already written and tested to solve specific types of problems usually designed by a central design agency CDA or purchased from a software firm or computer manufacturer PACKED DECIMAL In ASCII and EBCDIC the representation of two digits stored in one eight bit byte PAPER TAPE See punched tape PARALLEL TRANSMISSION A method of data transmission in which all bits of a particular character are transmitted simultaneously PARITY BIT A check bit an extra bit added to a group of bits for use in detecting errors during data transfer PARITY CHECK An internal erro
57. ACTERS EACH OCCUPYING TWO ADDRESS LOCATIONS VORD ADDRESSABLE Figure 4 9A Fixed word length vs variable word length storage FIXED LENGTH WORDS CONTAINING EIGHT CHARACTERS EACH OCCUPYING TWO ADDRESS LOCATIONS WORD ADDRESSABLE Another way to design the primary storage section is to store a single character such as the letter L or the number 8 in each address location An address is assigned to each location in storage Computers designed in this way are said to be character oriented or character addressable We also call them variable word length computers Therefore the name CHARLIE fig 4 9 view B now requires seven address locations 300 through 306 while amount paid 69 00 occupies six address locations 307 through 312 ADDRESS LOCATIONS 20 309 110 1 312 B VARIABLE LENGTH WORDS Figure 4 9B Fixed word length vs variable word length storage VARIABLE LENGTH WORDS CHARACTER ADDRESSABLE Whether a computer addresses a group of bytes as a word or addresses each byte individually is a function of the circuitry Both designs have advantages and disadvantages Variable word length computers make the most efficient use of available storage space since a character can be placed in every storage location In a fixed word length computer storage space may be wasted For example if the storage capacity in each address of a fixed word length computer is eight bytes and some of the data elements to be s
58. EADAVRITE CYLINDER 25 ARMS HEADS SURFACE 6 RECORD 1 A CYLINDER METHOD Figure 2 10A Physical organization of data on a disk CYLINDER METHOD Therefore to physically reference a record stored using the cylinder method a computer program must specify the cylinder number the recording surface number and the record number as shown in figure 2 10 view A Here the record is stored in cylinder 25 of recording surface 6 and is the first record on that track Special data stored on each track specifies the beginning of the track so that the first record second record third record and so on can be identified Another way to physically organize data on the disk pack and on diskettes is to use the sector method This requires that each of the tracks be divided into individual storage areas called sectors shown in figure 2 10 view B The number of sectors varies with the disk system used however there are usually eight or more Each sector holds a specific number of characters Before a record can be accessed a computer program must again give the disk drive the record s address specifying the track number the surface number and the sector number of the record One or more read write heads are then moved to the proper track the head over the specified surface is activated and the data is read from or written to the designated sector as it spins under the head TRACKS f 199 1 SECTOR SECTOR 6 B SECTOR METHOD
59. Fundamental flowcharting symbols GRAPHIC SYMBOLS Within a flowchart graphic symbols are used to specify arithmetic operations and relational conditions The following are commonly used arithmetic and relational symbols 3 13 plus add E minus subtract multiply divide plus or minus equal to gt greater than lt less than 2 greater than or equal to lt less than or equal to f not equal YES or Y Yes NO or N No TRUE or T True FALSE or F False FLOWCHARTING TEMPLATE To aid in drawing the flowcharting symbols you may use a flowcharting template Figure 3 4 shows a template containing the standard symbol cutouts A template is usually made of plastic with the symbols cut out to allow tracing the outline INPUT MANUAL PROCESSING AND AUXILIARY OPERATION PREDEFINED AND OR CONFORMS TO PROCESS OPERATION OUTPUT USA STANDARDS INSTITUTE X3 5 1966 ONLINE DISPLAY OUTPUT V C A STORACE FLOW FLOW DIR DIR Figure 3 4 Flowchart template FLOWCHART WORKSHEET The flowchart worksheet is a means of standardizing documentation It provides space for drawing programming flowcharts and contains an area for identification of the job including application procedure date and page numbers fig 3 5 You may find it helpful when you develop flowcharts If you don t have this form available a plain piece of p
60. ICATIONS SOFTWARE To use an applications program it must be compatible with the operating system Therefore the availability of application software for a particular operating system is critical Because of this several operating systems have become the most popular For 8 bit microcomputers CP M Control Program for Microprocessors is widely used because many hardware manufacturers have adopted it MS DOS MicroSoft Disk Operating System designed from CP M dominates in lower performance 16 bit systems UNIX an operating system for larger computers is being used on the more powerful 16 bit and 32 bit microcomputers Other operating systems are offered by microcomputer manufacturers To overcome the applications software compatibility problem some software comes in several versions so it can be run under several different operating systems The point to remember is that not all applications software will run on all systems You have to check to see that compatibility exists You need the right version OPERATING SYSTEM FUNCTIONS To give you a better idea of what you can expect to see on your microcomputer display screen we will show a few fundamental disk operating system commands and messages Again the functions of each operating system are about the same but each may use a different command to do about the same thing For example try not to get confused because CP M uses the command PIP peripheral interchange program to copy a file w
61. LENGTH OO O00 0000 DOUBLE WORD REFREENTS TWO FULL COMPUTER WORDS FOR ADDRESSING PURPOSES AS 4 UNIT OF STORAGE USED SOME OF THE LARGER MAIMFE AIME COMPUTERS AMD OM ALL SUPER COMPUTERS 64 BIT IM LENGTH VARIABLE FIXED Figure 4 10 Word lengths used on flexible byte addressable computers By now you should have a good idea of how primary storage locations are identified by their storage addresses how these addressable storage locations are used and how the storage capacity at an address can vary depending on the design of the computer Now let s go one step further to see how these bits and bytes are represented coded on some of the more common secondary storage media SECONDARY STORAGE DATA ORGANIZATION Remember secondary storage devices also called auxiliary or mass storage devices are those devices which are not part of the central processing unit cpu They include external core semiconductor thin film and bubble memories punched cards paper tape and several different types of mass storage such as magnetic tape disk and drum You already know it takes a certain number of bits to make one byte normally eight and when bytes are grouped together at a single address they make up a word in the computer s memory When data 4 13 is recorded on some type of magnetic storage medium such as disk or tape it is normally organized by bits characters bytes fields records and files
62. MPUTERS All analog computers are special purpose computers They are designed to measure continuous electrical or physical conditions such as current voltage flow temperature length or pressure They then convert these measurements into related mechanical or electrical quantities The early analog computers were strictly mechanical or electromechanical devices They did not operate on digits in binary notation either of the characters 0 and 1 If digits were involved at all they were obtained 1 6 indirectly Your wrist watch 1f nondigital your car s speedometer and oil pressure temperature and fuel gauges are also considered analog computers The output of an analog computer is often an adjustment to the control of a machine such as an adjustment to a valve that controls the flow of steam to a turbine generator or a temperature setting to control the ovens in the ship s galley for baking Analog computers are also used for controlling processes To do so they must convert analog data to digital form process it and then convert the digital results back to analog form You should know that a digital computer can process data with greater accuracy than an analog computer but an analog computer can process data faster than a digital computer in some systems Some computers combine the functions of both analog and digital computers They are called hybrid computers DIGITAL COMPUTERS Digital computers perform arithmetic and logi
63. Managers ECMs and other senior personnel technical references instructions etc and either the occupational or naval standards which are listed in the Manual of Navy Enlisted Manpower Personnel Classifications and Occupational Standards NAV PERS 18068 THE QUESTIONS The questions that appear in this course are designed to help you understand the material in the text VALUE In completing this course you will improve your military and professional knowledge Importantly it can also help you study for the Navy wide advancement in rate examination If you are studying and discover a reference in the text to another publication for further information look it up 1998 Edition Prepared by FCCM SW Robert A Gray Published by NAVAL EDUCATION AND TRAINING PROFESSIONAL DEVELOPMENT AND TECHNOLOGY CENTER NAVSUP Logistics Tracking Number 0504 LP 026 8450 Sailor s Creed I am a United States Sailor will support and defend the Constitution of the United States of America and will obey the orders of those appointed over me represent the fighting spirit of the Navy and those who have gone before me to defend freedom and democracy around the world proudly serve my country s Navy combat team with honor courage and commitment am committed to excellence and the fair treatment of all TABLE OF CONTENTS CHAPTER PAGE 1 Operational Concepts nsis IRE ER Eo e eedem 1 1 2 Hardware iacere te ette mi
64. NONRESIDENT TRAINING COURSE SEPTEMBER 1998 Navy Electricity and Electronics Training Series Module 22 Introduction to Digital Computers NAVEDTRA 14194 DISTRIBUTION STATEMENT A Approved for public release distribution is unlimited Although the words he him and his are used sparingly in this course to enhance communication they are not intended to be gender driven or to affront or discriminate against anyone DISTRIBUTION STATEMENT A Approved for public release distribution is unlimited PREFACE By enrolling in this self study course you have demonstrated a desire to improve yourself and the Navy Remember however this self study course is only one part of the total Navy training program Practical experience schools selected reading and your desire to succeed are also necessary to successfully round out a fully meaningful training program COURSE OVERVIEW To introduce the student to the subject of Digital Computers who needs such a background in accomplishing daily work and or in preparing for further study THE COURSE This self study course is organized into subject matter areas each containing learning objectives to help you determine what you should learn along with text and illustrations to help you understand the information The subject matter reflects day to day requirements and experiences of personnel in the rating or skill area It also reflects guidance provided by Enlisted Community
65. S Devices for reading data and programs into the computer system for processing INPUT OUTPUT DEVICES Secondary storage devices for writing and reading data Magnetic tape drives magnetic disk drives and drums are examples INTEGRATED CIRCUIT A miniaturized chip in which semiconductor components and other such technology combine the functions of a number of conventional components such as transistors resistors capacitors and diodes INTERNAL STORAGE MEMORY See storage primary INTERRECORD INTERBLOCK GAP A blank section of recording surface separating each record or block of records on a magnetic data medium K An abbreviation for the value 1 024 which is 210 Often used to express the memory capacity of a computer For example a 512K computer has 524 288 bytes of memory KEY TO DISK A process similar to key to tape in which data is transmitted from a keyboard to magnetic disk KEY TO TAPE An operation in which data is transmitted from a keyboard to magnetic tape LANGUAGE TRANSLATOR A program that reads a source program and converts it into an object machine language program Assemblers and compilers are examples LOCAL AREA NETWORK A network that normally operates within a well defined and generally self enclosed area The communication stations or terminals are usually linked by cable and are within 1 000 feet of each other AI 5 LOGICAL RECORD A record that includes all the data that be
66. STIC BASE B ONE GAP READ WRITE HEAD SIDE VIEW TAPE WRITE MOTION GAP READ GAP C TWO GAP READ WRITE HEAD Figure 2 19 Read write head assemblies 2 2 The major differences between magnetic tape units are the speed at which the tape is moved past the read write head and the density of the recorded information You know that density describes the number of binary digits bytes or frames we can record on an inch of tape The most common tape densities are 800 and 1 600 BPI or FPI Tape speed or tape movement varies to a great extent from less than 50 inches per second to more than 100 inches per second How fast a tape unit reads and writes is specified as the character transfer rate which is calculated by multiplying the speed of the magnetic tape unit by the character density MAGNETIC DISK DRIVE UNITS INPUT OUTPUT Magnetic disk drive units are storage devices that read and write information on the magnetized surfaces of rotating disks fig 2 20 The disks are made of thin metal coated on each side so that data can be recorded in the form of magnetized spots As the disks spin around like music records characters can be stored on them or retrieved in a direct manner This direct accessing of data has a big advantage over the sequential accessing of data It gives us fast immediate access to specific data without having to examine each and every record from the beginning You can direct the disk drive to begin
67. STRAP 1 A set of instructions that causes additional instructions to be loaded until the complete computer program is in storage 2 A technique or device designed to bring itself into a desired state by means of its own action e g a machine routine whose first few instructions are sufficient to bring the rest of itself into the computer from an input device 3 That part of a computer program used to establish another version of the computer program BUG A mistake in a program BYTE A group of bits next to each other that is considered a unit for example an 8 bit byte CENTRAL PROCESSING UNIT cpu The part of the computer hardware that directs the sequence of operations interprets the coded instructions performs arithmetic and logical operations and initiates the proper commands to the computer circuits for execution It controls the computer operation as directed by the program it is executing CHARACTER One symbol for example Z 2 0 1 9 CHIP A small piece of silicon impregnated with impurities in such a way as to form transistors diodes and resistors Electrical paths are formed on the silicon by depositing thin layers of aluminum or gold COBOL COmmon Business Oriented Language A high level programming language designed for business type applications COMPATIBLE SOFTWARE Programs that can be run on more than one type of computer These programs come in several different versions so they c
68. a it will use in its computations The process by which these instructions and data are read into the computer is called loading Actually the first step in loading instructions and data into a computer 1s to manually place enough instructions into memory using the keyboard or electronically using an operating system discussed in chapter 1 so that these instructions can be used to bring in more instructions as desired In this manner a few instructions are used to bootstrap more instructions Some computers make use of an auxiliary wired memory that permanently stores the bootstrap program thereby making manual loading unnecessary The memory internal storage section of a computer is essentially an electronically operated file cabinet It has a large number usually several hundred thousand of storage locations each referred to as a storage address or register Every item of data and program instruction read into the computer during the loading process is stored or filed in a specific storage address and is almost instantly accessible Q 1 What is the brain of a computer system Q 2 How many sections make up the central processing unit Q 3 What are the names of the sections that make up the cpu Q 4 The control section can be compared to what Q 5 What are the four major types of instructions in the control section 6 What capability allows the arithmetic logic section to test various conditions encountered durin Ip 8 proc
69. a modem know when to expect data Q 40 Whenever data is transferred between devices it involves the exchange of prearranged signals what is this process called SUMMARY Congratulations You have just finished the last chapter in Introduction to Digital Computers In this chapter you learned about many things that were mentioned in other chapters without a detailed explanation This was done intentionally as some of the subjects would have been too difficult and hard to understand without background knowledge Through your study of chapters 1 2 and 3 you gained enough knowledge to understand chapter 4 This chapter should have answered a lot of questions for you and made certain subjects more clear DATA is a general term used to describe raw facts like your service number name and paygrade SOURCE DATA is raw data typically written on some type of paper document DATA REPRESENTATION is accomplished by the use of symbols The symbol itself is not the information but merely a representation of it Symbols convey meaning only when understood In computers symbols are represented by CODES COMPUTER CODING SYSTEMS are used to represent numeric alphabetic and special characters in computer storage and on magnetic media EXTENDED BINARY CODED DECIMAL INTERCHANGE CODE EBCDIC is an 8 bit code used in computers to represent numbers letters and special characters AMERICAN STANDARD CODE FOR INFORMATION INTERCHANGE ASCID is another 8
70. a single set of start and sto message characters per block of data is which of the following types 1 Synchronous 2 Asynchronous 3 Microwave link 4 Frequency modulated Whenever data is transferred between devices it also involves an exchange of prearranged signals known as what 1 Nodding 2 Spacing 3 Handshaking 4 Coordinating The specific set of rules used to govern handshaking and message characters is called what 1 Sending 2 Protocol 3 Modulator 4 Transmitting
71. age Two methods are used asynchronous and synchronous With asynchronous transmission each character of data must be surrounded by message characters As a result more total bits must be transmitted transferred than would be necessary if the synchronous method were used With synchronous transmission only a single set of start and stop message characters is needed per block of data thus allowing more characters to be transmitted per second As you can see synchronous transmission is more efficient and faster However it has the disadvantage of requiring a more complex and expensive modem than does asynchronous transmission You should be aware that whenever data is transferred between devices it also involves an exchange of prearranged signals This is known as handshaking These signals in combination with a prearranged pattern of message characters define the rules for exchanging data over a communications line The exact rules depend upon each individual computer manufacturer the telephone company and the related devices the modems that make up the computer system Protocol 1s the term used for the specific set of rules that govern handshaking and message characters In the system illustrated in figure 4 14 data to be sent to the main computer s cpu is entered through a remote online user terminal far left As the data is keyed it 1s keyed in digital form and sent to a nearby modem to be converted into an analog signal suitable
72. ail here You will have documentation and reference manuals for the specific version of the operating system you will be using Q 1 What is the heart of any computer system Q 2 Which types of operating systems are the simplest and most common on microcomputers Q 3 What types of operating systems let more than one user access the same resources at the same time Q 4 Why is the availability of applications software for a particular operating system critical Q 5 How is the applications software compatibility problem overcome UTILITY PROGRAMS Now that you have learned about operating systems let s go into another type of program utilities In addition to the utility commands like diskcopy and rename which are built into the operating system you will probably have some independent utility programs These are standard programs that run under control of the operating system just like your applications programs They are called utilities because they perform general types of functions that have little relationship to the content of the data Utility programs eliminate the need for programmers to write new programs when all they want to do is copy print or sort a data file Although a new program is not needed we do have to tell the program what we want it to do We do this by providing information about files data fields and the process to be used For example a sort program arranges data records in a specified order You will have to
73. allows you to enter data and then retrieve it in a variety of ways 1 Communications 2 Data retrieval 3 Data management 4 Document compilation 21 QUESTIONS 3 59 AND 3 60 ARE TO BE JUDGED TRUE OR FALSE 3 59 3 60 Spreadsheets are tables of rows and columns of text 1 True 2 False You can use all printers for graphics output 1 True 2 False Assignment 4 Assignment Topic 4 Pages 4 1 through 4 17 4 1 In using a digital computer 4 2 4 3 4 4 which of the following is one of the major problems we face 1 Finding disks to fitthe drives 2 Locating a stable power source 3 Communicating with the computer 4 Arranging the proper environment In computer terminology what is a general term to describe raw facts Characters 2 Bits 3 Bytes 4 Data In computer terminology when data has been processed with other facts and has meaning it is described as which of the following 1 Information only the computer can understand and properly use 2 Information we can understand and properly use 3 Information the input device can understand and properly use 4 Information the output device can understand and properly use Data is represented by which of the following means By symbols By electricity By magnetics By mechanics BONS Data Representation and Communications QUESTION 4 5 IS TO BE JUDGED TRUE OR FALSE 22 4 5 4 6 4 7
74. an be run under several different operating systems COMPILER A program that translates source programs written in a high level programming language for example COBOL or FORTRAN into machine language COMPUTER A programmable electronic device that can store retrieve and process data COMPUTER OPERATOR The person who sets up and operates the computer system COMPUTER PROGRAMMER A person who designs writes tests debugs and documents programs COMPUTER SYSTEM The cpu mainframe with its console input and output devices and secondary auxiliary storage devices COMPUTER USERS See users COMPUTER WORD See word computer AI 2 CONSOLE The unit of the computer used by the computer operator to communicate with and control the computer system CONTROL SECTION The part of the cpu that directs the flow of operations and data maintains order in the computer and initiates execution of the instructions CRT Cathode Ray Tube TERMINAL A computer terminal that displays its output on a television like screen that may be black and white or color CURSOR A pointer a dot of light on a crt screen to let you know the next position in which data will be entered By depressing cursor control keys the operator can move the cursor from line to line and from character to character CUSTOM SOFTWARE Programs designed and written to the specifications of a user or an organization DATA Facts represente
75. aper will do 3 14 Programmer Program No Chart ID Chart Name Program Name Figure 3 5 Flowchart worksheet Constructing a Flowchart There is no best way to construct a flowchart There is no way to standardize problem solution Flowcharting and programming techniques are often unique and conform to the individual s own methods or direction of problem solution This section will show an example of developing a programming flowchart It is not the intent to say this is the best way rather it is one way to do it 3 15 By following this text example you should grasp the idea of solving problems through flowchart construction As you gain experience and familiarity with a computer system these ideas will serve as a foundation To develop a flowchart you must first know what problem you are to solve It is then your job to study the problem definition and develop a flowchart to show the logic steps and sequence of steps the computer is to execute to solve the problem As an example suppose you have taken a short term second mortgage on a new home and you want to determine what your real costs will be the amount of interest the amount to be applied to principal and the final payment at the end of the 3 year loan period The first step is to be sure you understand the problem completely What are the inputs and the outputs and what steps are needed to answer the questions Even when you are specifying a problem of y
76. aracters such as amp and yes even the comma The data to be represented is called source data Figure 4 1 Communications symbols SOURCE DATA Source data or raw data is typically written on some type of paper document which we refer to as a source document The data contained on the source document must be converted into a machine readable form for processing either by direct or indirect means The data may be entered directly into the computer in its original form namely right from the source document on which it is recorded by way of magnetic ink characters optically recognizable characters or bar code recognition Or the data on the documents may be entered indirectly on input media such as punched cards paper tape magnetic tape or magnetic disk It may also be keyed directly into a computer from a keyboard If you look at figure 4 2 you see a list of SERVMART items that have been typed on a preprinted form To most people this is just another piece of paper however to the Storekeeper SK it is a source document to be used to provide input data to the computer In this example the SERVMART form deals with requisitioning supplies The form could be sent to the data entry department to be used as a source document There the data entry operator can key the data into or on whatever computer medium is to be used according to a prescribed format The data elements are numbered in the order they are to be keyed
77. are stored Different character sets may be displayed by simply replacing the appropriate ROM or PROM chips with new chips containing different character patterns Upon receipt of a character code and a row and column address the device logic reads the picture element pattern dot matrix from the ROM and writes the pattern into the appropriate character position in the page memory The desired character is then displayed at the correct position Other display devices store the codes in page memory and convert the codes to picture element dots when scanning memory to refresh or redisplay the characters on the screen The use of formatted displays greatly simplifies the programming requirements for the display of alphanumeric data Flat Panel Displays A number of display methods are in use that are designed to reduce the depth of the crt display caused by the length of the tube These devices are collectively known as flat panel displays Three types of flat panel displays commonly in use with computer systems are liquid crystal displays LCDs gas plasma displays GPDs and electroluminescent displays ELDs The screens of these flat panel displays are made up of pairs of electrodes Each pair of electrodes is used to generate one picture element 2 31 The liquid crystal display differs from the gas plasma and electroluminescent displays in that it does not generate its own light for the picture elements The LCD requires an external light so
78. arises Data and programs can be retrieved over and over again without destroying the contents of the EPROM They will stay there quite safely until you want to reprogram it by first erasing the EPROM with a burst of ultra violet light This is to your advantage because if a mistake is made while programming the EPROM it is not considered fatal The EPROM can be erased and corrected Also it allows you the flexibility to change programs to include improvements or modifications in the future Q 17 In what type of memory are often used instructions and programs permanently stored inside the computer Q 18 Who provides the programs stored in ROM Q 19 Can programs in ROM be changed Q 20 What is another name for random access memory RAM Q 21 How is data read from or written into RAM Q 22 In what two states can programmable read only memory PROM be purchased Q 23 What is the main disadvantage of PROM Q 24 What does EPROM stand for Q 25 How is EPROM erased 2 8 SECONDARY STORAGE The last kind of memory we will briefly introduce here is called secondary storage or auxiliary storage This is memory outside the main body of the computer cpu where we store programs and data for future use When the computer is ready to use these programs and data they are read into internal storage Secondary auxiliary storage media extends the storage capabilities of the computer system We need it for two reasons First because the co
79. at is a string of numbers which represents the instruction code and operand addresses is what type 1 Machine 2 Printed 3 Symbolic 4 Procedure oriented Mnemonic instruction codes and symbolic addresses were developed early in what decade 1 1940s 2 1950s 3 1960s 4 1970s 3 20 Compared to machine language coding symbolic languages have which of the following advantages 1 Detail is reduced Fewer errors are made 3 Less time is required to write a program 4 Allofthe above 3 21 An instruction that allows the programmer to write a single instruction which is equivalent to a specified sequence of machine instructions is what type of instruction 1 Machine language instruction 2 Graphic language instruction 3 Macroinstruction 4 Scientific instruction 3 22 What does the acronym COBOL stand for 1 Computer ordered byte oriented language 2 Computer ordered business oriented language 3 Common business oriented language 4 Common business ordered language 3 23 PASCAL is being used by many colleges and universities to teach programming for which of the following reasons 1 Itis fairly easy to learn and more powerful than BASIC 2 Itis hard to learn and weaker than BASIC 3 It is easy to learn and cheaper than BASIC 4 It is a shorter course and produces better programmers 3 24 The development of Ada was initiated by what organization U S Navy U S Army U S Department
80. at represent data or program instructions Punched cards can be read by an input device card reader to a computer PUNCHED TAPE A tape punched with hole patterns that represent data or program instructions Tape can be read by an input device to a computer RAM Acronym for random access memory RANDOM ACCESS A method of accessing data or instructions without having to scan any preceding information Magnetic core semiconductor and bubble memories are considered random access storage devices REAL TIME PROCESSING A computer processing method in which data about a particular event is entered directly into the computer as the event occurs and is immediately processed so it can influence future processing RECORD A group of related fields all pertaining to the same subject RECORD BLOCK Several records blocked together RECORD LENGTH The number of characters in a record REMOTE TERMINAL A display terminal such as a crt or other piece of equipment which is not located with the computer but is connected by a communications line In a typical online real time communications system the remote device is usually a teletypewriter or a crt visual display unit ROM Acronym for read only memory ROTATIONAL DELA Y The time required for the read write head to find a specified record on a disk diskette or drum once head positioning has occurred SECONDARY STORAGE See storage secondary SECTORS The pie shape
81. ata internally in microcomputers The concepts and advantages of ASCII are identical to those of EBCDIC The important difference between the two coding systems lies in the 8 bit combinations assigned to represent the various alphabetic numeric and special characters When using ASCII 8 bit code you will notice the selection of bit patterns used in the positions differs from those used in EBCDIC For example let s look at the characters DP3 in both EBCDIC and ASCII to see how they compare Character D P 3 EBCDIC 1100 0100 1101 0111 1111 0011 ASCII 0100 0100 0101 0000 0011 0011 In ASCII rather than breaking letters into three groups uppercase letters are assigned codes beginning with hexadecimal value 41 and continuing sequentially through hexadecimal value 5A Similarly lowercase letters are assigned hexadecimal values of 61 through 7A The decimal values 1 through 9 are assigned the zone code 0011 in ASCII rather that 1111 as in EBCDIC Figure 4 7 is the ASCII coding chart showing uppercase and lowercase alphabetic characters and numeric digits 0 through 9 4 6 ALPHABETIC CHARACTERS UPPERCASE PRINTS B c D E F G H i 2 L M N o f d de de dme Ge deo dh ode Gh oS dx TP Oy CB Ode UG 4 QN QM detur Rae 7 O3 oe omo cud one 0 Uam Aon US OS Oh US oh OS OU Top 07 Ww I 00 b Ch XGA de RS Ree Flog wo cu ag a e
82. ation 1 10 fourth generation and beyond 1 12 second generation 1 10 third generation 1 11 Computer stored program 2 3 Computer using a desktop 1 17 to 1 21 operating system 1 18 storage media handling and backup 1 19 Computers classification of 1 3 to 1 9 accuracy of computers 1 7 to 1 9 analog computers 1 6 digital computers 1 6 to 1 7 electromechanical computers 1 4 electronic computers 1 5 general purpose computers 1 6 mechanical computers 1 3 special purpose computers 1 6 Computers history of 1 2 to 1 3 Control break 3 6 Control field 3 6 Control instructions 2 3 Cursor control key 2 28 Cylinder method 2 11 D Daisy wheel printers 2 25 Data flowcharts 3 11 Data management software 3 24 Data organization 4 10 to 4 14 Data representation and communications 4 1 to 4 22 computer coding systems 4 3 to 4 7 American Standard Code for Information Interchange ASCII 4 6 to 4 7 extended binary coded decimal interchange code EBCDIC 4 3 to 4 6 parity bit 4 7 to 4 8 data 4 1 to 4 3 data representation 4 1 to 4 2 source data 4 2 to 4 3 INDEX 1 Data representation and communications Continued data storage concepts 4 8 to 4 15 bits and bytes 4 8 magnetic core storage 4 9 to 4 10 secondary storage data organization 4 13 to 4 15 storage capacity and addresses 4 10 to 4 13 networks 4 16 to 4 19 local area networks LANs 4 16 to 4 17 modems 4 17 to 4 18 wide area netwo
83. be processed is found 2 The location where the result of processing is to be stored 3 The location where the next instruction to be executed is found When this type of operand is not specified the instructions are executed in sequence The number of operands and the structure or format of the instructions vary from one computer to another However the operation always comes first in the instruction and is followed by the operand s The programmer must prepare instructions according to the format required by the language and the computer to be used 3 18 Instruction Set The number of instructions in a computer s instruction set may range from less than 30 to more than 100 These instructions may be classified into categories by the action they perform such as input output I O data movement arithmetic logic and transfer of control Input output instructions are used to communicate between I O devices and the central processor Data movement instructions are used for copying data from one storage location to another and for rearranging and changing of data elements in some prescribed manner Arithmetic instructions permit addition subtraction multiplication and division They are common in all digital computers Logic instructions allow comparison between variables or between variables and constants Transfer of control instructions are of two types conditional and unconditional Conditional transfer of control instructions are
84. before giving them to the processor This would be fine so far as the computer is concerned however it would be very awkward for the programmer Another approach is a compromise between the programmer and computer The programmer first writes instructions in a code that 1s easier to relate to English This code is not the computer s language therefore the computer does not understand the orders The programmer solves this problem by giving the computer another program one that enables it to translate the instruction codes into its own language This translation program for example would be equivalent to an English to French dictionary leaving the translating job to be done by the computer The third and most desirable approach from an individual s standpoint is for the computer to accept and interpret instructions written in everyday English terms Each of these approaches has its place in the evolution of programming languages and is used in computers today MACHINE LANGUAGES With early computers the programmer had to translate instructions into the machine language form that the computers understood This language was a string of numbers that represented the instruction code and operand address es In addition to remembering dozens of code numbers for the instructions in the computer s instruction set the programmer also had to keep track of the storage locations of data and instructions This process was very time consuming quite expe
85. bility Different word lengths such as half word full word and double word are possible with what type of computer 1 Bit addressable 2 Byte addressable 3 File addressable 4 Record addressable When a flexible computer is working in a fixed word length environment each address identifies what group of elements that can be operated on as a unit Bits 25 Bytes 3 Files 4 Records To automatically retrieve manipulate and store a fixed word of data as a unit on a flexible computer what means can a programmer use 1 Parity bit 2 Program length 3 Storage capacity 4 Program instructions In computer terminology a grou of related bits is known by whic of the following terms 1 Word 2 File 3 Record 4 Character What group of related items form a record 1 Bits 2 Bytes 3 Fields 4 Characters 4 35 4 36 4 37 4 38 4 39 4 40 The variations in how data files are stored in storage is determined by what 1 Types of media and devices used 2 Cost of the installation 3 Size of the installation 4 Type of power available When you store a file on tape the 125th record cannot be read until the 124 records in front of it are read This is called what type of storage Input access Direct access Random access Sequential access When data can be obtained quickly from anywhere on the media without having to read the records
86. c functions on separate discrete data like numbers or combinations of discrete data such as name rate and division This makes them different from analog computers that operate on continuous data like measuring temperature changes We generally use digital computers for business and scientific data processing The following are examples Accounting Computers are ideal for keeping payroll records printing paychecks billing customers preparing tax returns and taking care of many of the other accounting tasks in an organization Recordkeeping Computers can record information like inventories and personnel files They can also keep track of books checked out of a library Airline ticket counters are much more efficient than they used to be thanks to centralized reservation computers that can be reached over the telephone lines Industrial Uses Industrial computers save considerable time and reduce waste by efficiently performing hundreds of industrial tasks ranging from filling sales orders and routing parts to various locations on an assembly line to designing earthquake resistant structures and controlling an entire oil refinery Science The research and development applications are the most numerous Digital computers are being used to do lengthy and complicated mathematical calculations millions of times faster than human beings They are also used to collect store and evaluate data from experiments analyze weather patterns
87. c tape units categorized 1 Type of packaging used for tape 2 Sizeoftape 3 Speed of tape 4 Costoftape What determines if a standard 1 2 inch tape will have either seven or nine tracks of data 1 The brand of tape The read write heads installed in the tape unit 3 Thetype of computer used 4 The speed at which the tape unit is run For multitrack tapes what is the range of common recording densities in bits bytes per inch bpi 1 From 200 to 6 250 bpi 2 From 300 to 6 275 bpi 3 From 400 to 6 300 bpi 4 From 500 to 6 350 bpi On magnetic tape the size of a record that holds the data is restricted in what two ways 1 By the thickness of the tape and the capacity of internal storage 2 Bythe length of the tape and the speed of internal storage 3 By the width of the tape and the speed of internal storage 4 Bythe length of the tape and the capacity of internal storage In computer terminology what is called a file A collection of tapes A collection of disks A collection of records A collection of characters PO 2 43 2 44 2 45 2 46 2 47 In order for data to be read from or written on a magnetic tape the tape must do what 1 Speed up 2 Move at a predetermined speed 3 Slow down 4 Stop Storing single records on a magnetic tape has which of the following disadvantages 1 It takes too long to record the data It takes too long to recover the data 3 Too much of
88. cal to protect the computer parts Compared to today s computers they had slow input and output devices were slow in processing and had small storage capacities Many of the internal processing functions were measured in thousandths of a second millisecond The software computer program used on first generation computers was unsophisticated and machine oriented This meant that the programmers had to code all computer instructions and data in actual machine language They also had to keep track of where instructions and data were stored in memory Using such a machine language see chapter 3 was efficient for the computer but difficult for the programmer Figure 1 6 First generation computers used vacuum tubes SECOND GENERATION The computers of the second generation 1959 1963 were characterized by transistors fig 1 7 instead of vacuum tubes Transistors were smaller less expensive generated almost no heat and required very little power Thus second generation computers were smaller required less power and produced a lot less heat The use of small long lasting transistors also increased processing speeds and reliability Cost performance also improved The storage capacity was greatly increased with the introduction of magnetic disk storage and the use of magnetic cores for main storage High speed card readers printers 1 10 and magnetic tape units were also introduced Internal processing speeds increased Functions were
89. can be updated by the work center supervisor Although the information is usually viewed on a display screen cathode ray tube printed hard copies can be obtained Today hard copy output from SNAP can be sent to higher authorities in lieu of written reports In the future these hard copy transmittals may be replaced by disks or tapes containing the same data In some cases the shipboard computers will have an extra telephone wire to the pier or tender and information can be exchanged electronically And there are other important benefits In practice the system expedites the storage and retrieval of information the Navy has about its ships In turn information that is more accessible means a more timely supply of parts an improved aid to planners on when and how long to schedule ships overhauls and updated information for making decisions whether to place additional or remove unnecessary shipboard equipment These decisions are now made by laboriously using stacks of printed files SNAP can sort through these files electronically so Navy planners can make more effective and timely decisions SNAP is a system for unclassified use only at present This cuts the costs of the installation and many of the physical and electronic security requirements Q 40 What is one of the more widespread uses of the computer Q 41 What is the great advantage of computers over typewriters Q 42 How are word processing programs used by the Navy Q 43
90. communications line It also converts the audio signal back to a digital signal before it is supplied to your terminal or computer ANSWERS TO QUESTIONS Q1 THROUGH Q40 1 Data A 2 By symbols A 3 Numbers A 4 By either direct or indirect means A 5 Punched cards paper tape magnetic tape or magnetic disk A 6 Extended Binary Coded Decimal Interchange Code A 7 256 A 8 16 A 9 Packing or packed data A 10 American Standard Code for Information Interchange 4 20 4 11 4 12 4 13 4 14 4 15 4 16 4 17 4 18 4 19 4 20 4 21 4 22 4 23 A 24 4 25 4 26 4 27 A 28 4 29 4 30 4 31 4 32 4 33 4 34 4 35 4 36 4 37 4 38 To standardize a binary code to give the computer user the capability of using several machines to process data regardless of the manufacturer No they are identical To detect errors in the circuitry Nine Program storage area By the individual programs being used A single binary digit Eight Number of bytes Magnetic cores are strung together on a screen of wire In primary storage The manufacturer Variable word length or byte addressable Fixed word length By bits characters bytes fields records and files A collection of related records Sequential access Direct access storage Magnetic core semiconductor thin film and bubble A network Exchange information A communications facility and interface units Two Broadband
91. d by numbers letters or symbols to which meaning is or can be assigned DATA BASE A structured collection of data that can be extracted organized and manipulated by a program DATA COMMUNICATIONS The means by which data is transmitted electronically from one location to another over a communications channel DATA ELEMENT One item of information the smallest unit of data that can be referenced DATA FLOWCHART See flowchart DATA REFERENCE The source document identification DATA REPRESENTATION The symbols and codes used by computers to represent letters numbers and special characters DEBUGGING The process of finding errors bugs in a program or system and correcting them so that the program or system runs correctly DENSITY RECORDING The number of bits bytes characters or frames per linear inch on a recording medium like tape or disk DIGITAL COMPUTER A computer that solves problems on discrete data using 0 s and 1 s OFF and ON states to represent data and operations DIRECT ACCESS A storage method that allows the computer to locate and read a particular record without having to search through an entire file The computer is able to access data independent of its location Magnetic disks diskettes and drums are considered direct access devices DISK DRIVE A direct access storage device for recording and retrieving data on hard rigid disk or floppy disks diskettes DISK PACK A mass st
92. d od nd 0 h me eB He se ap oj d uA Da BUR X Eon dB ndo NUMERIC CHARACTERS Figure 4 7 Eight bit ASCII coding chart including hexadecimal equivalents At this point you should understand how coding systems are used to represent data in both EBCDIC and ASCII Regardless of what coding system is used each character will have an additional bit called a check bit or parity bit PARITY BIT This additional check or parity bit in each storage location is used to detect errors in the circuitry Therefore a computer that uses an 8 bit code such as EBCDIC or ASCII will have a ninth bit for parity checking 4 7 The parity bit also called a check bit the C position in a code provides an internal means for checking the validity the correctness of code construction That is the total number of bits in a character including the parity bit must always be odd or always be even depending upon whether the particular computer system or device you are using is odd or even parity Therefore the coding 1s said to be in either odd or even parity code and the test for bit count is called a parity check Now let s talk about bits and bytes primary storage and storage capacities or to put it another way the capacity of a storage location Sit back keep your memory cycling and we will explain the ways data may be stored and retrieved inside the comp
93. d processing speed decreases 3 Storage space required decreases and processing speed increases 4 Storage space required decreases and processing speed decreases 4 14 Through the cooperation of several manufacturers what a bit code was developed for transmitting and processing data 1 EBCDIC 2 EBCDIC 3 ASCIT 4 ASCII QUESTION 4 15 IS TO BE JUDGED TRUE OR FALSE 4 15 The concepts and advantages of ASCII are identical to those of EBCDIC 1 True 2 False 4 19 4 20 4 21 4 22 23 The letter D is represented b what coding in a EBCDIC and b ASCII l a 1111 0011 D 20911 9011 2A 0011 9011 b 1111 99211 3 0100 0100 b 1100 0100 4 1109 9100 D 0100 01909 An additional bit in each storage location called a parity bit is used for what purpose 1 To stop errors 2 erase errors 3 To detect errors 4 To reroute errors The parity bitis also called what 1 Odd bit 2 Even bit 3 Code bit 4 Check bit The test for bitcount is called what 1 Odd check 2 Even check 3 Stop check 4 Parity check W hat storage area accepts and holds input data to be processed 1 Input 2 Output 3 Working 4 Program A single binary digit is called what 1 Bit 2 Byte 3 ord 4 Record What symbol is used when we refer to the size of computer memory ASNS ABE 4 23 When many magnetic cores are 4 29 strung together on a screen of w
94. d segments of a disk s recording surface SEQUENTIAL ACCESS A storage technique in which the stored items of information become available only in a one after the other sequence whether or not all the information or only some of it is desired Magnetic tape is an example SOFT COPY Output of a computer displayed on a display terminal or monitor crt It is nonpermanent SOFTWARE Programs routines codes and other written information used to direct the operation of a computer as distinguished from hardware AI 8 SORT The process of arranging data records in a predefined sequence by use of sort keys for example to sequence personnel records by social security number the sort key SOURCE DATA Tphe data in its initial state to be processed by a computer system SOURCE DOCUMENT The document that contains the initial raw data for computer processing SOURCE PROGRAM A computer program written in a language like COBOL FORTRAN or assembly language It must be translated into an object program before it can be executed by a computer SPECIAL PURPOSE COMPUTER A computer designed to perform one specific function such as a weather computer STORAGE PRIMARY MAIN INTERNAL The section of the cpu in which instructions and data are held Also called main memory STORAGE SECONDARY AUXILIARY EXTERNAL Storage outside the cpu where programs and data are stored for future computer processing for example tapes
95. d the outcome of the 1952 presidential election the term giant brain caused much confusion and uneasiness Many people assumed that science had created a thinking device superior to the human mind Currently most people know better By human standards the giant brain 1s nothing more than a talented idiot that is wholly dependent upon human instructions to perform even the simplest job A computer is only a machine and definitely cannot think for itself The field of artificial intelligence however is developing computer systems that can think that is mimic human thought in a specific area and improve performance with experience and operation The field of digital computers is still in the growing stages New types of circuitry and new ways of accomplishing things are continuing to be developed at a rapid rate In the military field the accomplishments of digital computers are many and varied One outstanding example is in weapons systems Most of the controlling 1s done by digital computers CLASSIFICATIONS OF COMPUTERS Computers can be classified in many different ways They can be classified by the type of technology they use mechanical electromechanical or electronic the purpose for which they were designed general purpose or special purpose by the type of data they can handle digital or analog by the amount they cost from 50 to 10 million and up and even by their physical size handheld to room size We will briefly expla
96. d to represent data The coding systems included are Extended Binary Coded Decimal Interchange Code EBCDIC and American Standard Code for Information Interchange ASCII EXTENDED BINARY CODED DECIMAL INTERCHANGE CODE EBCDIC Using an 8 bit code it is possible to represent 256 different characters or bit combinations This provides a unique code for each decimal value 0 through 9 for a total of 10 each uppercase and lowercase letter for a total of 52 and for a variety of special characters In addition to four numeric bits four zone bit positions are used in 8 bit code as illustrated in figure 4 3 Each group of the eight bits makes up one alphabetic numeric or special character and is called a byte 4 3 ZONE BITS NUMERIC BITS Z 2 2 2 8 4 2 1 Figure 4 3 Format for EBCDIC and ASCII codes When you look at figure 4 3 you will notice that the four rightmost bits in EBCDIC are assigned values of 8 4 2 and 1 The next four bits to the left are called the zone bits The EBCDIC coding chart for uppercase and lowercase alphabetic characters and for the numeric digits 0 through 9 is shown in figure 4 4 with their hexadecimal equivalents Hexadecimal is a number system used with some computer systems It has a base of 16 0 9 and A F A represents 10 B represents 11 C represents 12 D represents 13 E represents 14 and F represents 15 In EBCDIC the bit pattern 1100 is the zone combination used for the alphabetic character
97. des Some systems can only do one task at a time while others can perform several at a time Some systems allow only one person to use the system and others allow multiple users Single user single tasking operating systems are the simplest and most common on microcomputers CP M amp 80 CP M 86 and MS DOS are examples Single user multitasking operating systems allow you to do more than one task as long as the tasks don t use the same type of resources For example you can print one job while you run another as long as the second job does not require the printer Examples are Concurrent CP M 86 Concurrent amp DOS and MS DOS 3 0 and above Multiuser multitasking operating systems let more than one user access the same resources at the same time This is especially useful for sharing common data These are only feasible on processors the functional unit in a computer that interprets and executes instructions of 16 bits or more and with large memories UNIX is an example There are also multiprocessor systems shared resource systems This means each user or operator has a dedicated microprocessor cpu which shares common resources disks printers etc 1 CP M and CP M 86 are registered trademarks of Digital Research Inc 2 MS DOS is a registered trademark of Microsoft Corporation 3 Concurrent CP M and Concurrent DOS are trademarks of Digital Research Inc 4 UNIX is a trademark of AT amp T COMPATIBILITY WITH APPL
98. ding corrections needed When the program passes these tests it 1s ready for computer implementation Before computer implementation takes place documentation must be completed Documentation Documentation is a continuous process beginning with the problem definition Documentation involves collecting organizing storing and otherwise maintaining a complete record of the programs and other documents associated with the data processing system The Navy has established documentation standards to ensure completeness and uniformity for computer system information between commands and between civilian and Navy organizations SECNAVINST 5233 1 establishes minimum documentation requirements 3 21 A documentation package should include 1 A definition of the problem Why was the program written What were the objectives Who requested the program and who approved it These are the types of questions that should be answered 2 A description of the system The system environment hardware software and organization in which the program functions should be described including systems flowcharts General systems specifications outlining the scope of the problem the form and type of input data to be used and the form and type of output required should be clearly defined 3 A description of the program Programming flowcharts program listings program controls test data test results and storage dumps these and other docume
99. down notes read them and rub them out when you are finished with them In the computer RAM is the working memory Data can be read retrieved from or written stored into RAM just by giving the computer the address of the location where the data is stored or is to be stored When the data is no longer needed you can simply write over it This allows you to use the storage again for something else Core semiconductor and bubble storage all have random access capabilities PROGRAMMABLE READ ONLY MEMORY PROM An alternative to ROM is programmable read only memory PROM that can be purchased already programmed by the manufacturer or in a blank state By using a blank PROM you can enter any program into the memory However once the PROM has been written into it can never be altered or changed Thus you have the advantage of ROM with the additional flexibility to program the memory to meet a unique need The main disadvantage of PROM is that if a mistake is made and entered into PROM it cannot be corrected or erased Also a special device is needed to burn the program into PROM ERASABLE PROGRAMMABLE READ ONLY MEMORY EPROM The erasable programmable read only memory EPROM was developed to overcome the drawback of PROM EPROMS can also be purchased blank from the manufacturer and programmed locally at your command activity Again this requires special equipment The big difference with EPROM is that it can be erased if and when the need
100. ductor storage the silicon chip 2 6 Single user multitasking operating systems 3 2 Single user single tasking operating systems 3 2 SNAP II 1 15 Software 3 1 to 3 29 operating systems 3 1 to 3 4 INDEX 4 Software Continued compatibility with applications software 3 2 operating system functions 3 2 to 3 4 types of operating systems 3 2 packaged software 3 23 to 3 27 data management 3 24 to 3 25 graphics 3 26 to 3 27 spreadsheets 3 25 to 3 26 word processing 3 23 to 3 24 programming 3 8 to 3 22 flowcharting 3 11 to 3 18 constructing a flowchart 3 15 to 3 18 tools of flowcharting 3 12 to 3 14 overview of programming 3 9 to 3 11 program coding 3 18 to 3 22 coding a program 3 19 to 3 21 debugging 3 21 documentation 3 21 to 3 22 implementation 3 22 instruction set 3 19 instructions 3 18 testing 3 21 programming languages 3 6 to 3 8 machine languages 3 6 to 3 7 procedure oriented languages 3 7 to 3 8 symbolic languages 3 7 utility programs 3 4 to 3 6 report program generators 3 5 to 3 6 sort merge programs 3 4 to 3 5 Sort merge programs 3 4 to 3 5 Source document 4 2 to 4 3 Spelling checker 3 23 Spreadsheets 3 25 Storage access methods 4 15 to 4 16 direct access storage 4 15 random access storage 4 16 sequential access storage 4 15 Storage auxiliary see storage secondary Storage internal 2 4 to 2 7 addressing 4 13 to 4 15 Storage internal Continued bubble storage
101. e such as magnetic core storage others were electronic such as semiconductor and bubble storage For purposes of simplicity we have selected magnetic core storage to show you how data is represented and stored in the computer s primary memory BITS AND BYTES A bit is a single binary digit It represents the smallest unit of data just like the good old American penny However computers usually do not operate on single bits rather they store and manipulate a fixed number of bits Most often the smallest unit or number of bits a computer works with is eight bits These eight bits make up a byte You just learned that both EBCDIC and ASCII codes use eight bits excluding the parity bit and that eight bits represent a single character such as the letter A or the 4 8 number 7 Thus the computer can store and manipulate an individual byte a single character or a group of bytes several characters a word at a time These individual bytes or groups of bytes form the basic unit of memory Primary storage capacities are usually specified in number of bytes The symbol K is used whenever we refer to the size of memory especially when the memory is quite large The symbol K is equal to 1 024 units or positions of storage Therefore if a computer has 512K bytes not bits of primary storage then it can hold 512 x 1 024 or 524 288 characters bytes of data in its memory MAGNETIC CORE STORAGE In primary storage many magnetic cores ar
102. e you may be answering inquiries or putting together contracts or proposals Once you select the standard paragraphs you want you add variable information This saves both keying and proofreading time Communications software and hardware enable you to transmit and receive text on your microcomputer Many organizations use this capability for electronic mail In a matter of minutes you can enter and transmit a memo to other commands or to personnel in other locations You can transmit monthly reports notices or any documents prepared on the microcomputer DATA MANAGEMENT Data management software allows you to enter data and then retrieve it in a variety of ways You define your data fields and set up a display screen with prompts Y ou enter the data records according to the prompts Figure 3 9 view A shows an example The system writes the records on a disk or tape Once you have a file keyed and stored you can retrieve records by a field or several fields or by searching the records for specific data For example if you wanted a list of all personnel who reported aboard before January 1988 you could tell the system to search the file and print selected fields of all records that meet that condition You tell the system what fields to print that is name rate SSN date reported and where what print positions to print them At the same time you can specify in what order you want the records printed For example figure 3 9 view B shows t
103. e containing supply inventory records is called a supply inventory file Records can be placed on tape either separately as single records unblocked as shown in figure 2 15 view A or multiple records can be grouped together blocked as shown in figure 2 15 view B to form a record block The number of records stored in a record block is the blocking factor In this example the blocking factor is five 2 15 oauoomza oaoomza 1 2 4 5 6 7 8 10 12 13 14 15 oauoomza oazoomza ozoomz c JC B BLOCKED MULTIPLEJRECORDS WITH A BLOCKING FACTOR OF FIVE f5 Figure 2 15 Record formats on magnetic tape All magnetic tape must be moving at a predetermined speed for data to be read from or written on the tape Data cannot be read or written while the tape is coming up to speed slowing down or stopped During this time delay the tape moves a short distance creating a blank spot on the tape This interrecord gap or interblock gap separates each single record or block of records on the tape The length of the gap varies depending upon the particular system and method of recording but is approximately 2 5 to 3 4 inch in length If single records are stored on the tape the interrecord gap may be longer than the portion of tape used to store the record Therefore much of the tape s recording surface is wasted To overcome the inefficiency of storing s
104. e extent on the mechanical process involved It is usually necessary to scan some but not all of the preceding data 4 15 RANDOM ACCESS STORAGE Random access storage media refers to magnetic core semiconductor thin film and bubble storage Here a given item of data can be selected from anywhere in storage without having to scan any preceding items And the access time is independent of the storage location Q 27 Punched cards paper tape and magnetic tape use what storage access method Q 28 What kind of storage allows you to access the 125th record without having to read the 124 records in front of it Q 29 Random access storage media refers to what types of storage NETWORKS A network can be defined as any system composed of one or more computers and terminals however most are composed of multiple terminals and computers In this section you will learn how this allows dissimilar computers to work together as a team LOCAL AREA NETWORKS LANs In local area networks LANs various machines are linked together within a building or adjacent buildings Figure 4 12 shows an example of a LAN A LAN allows dissimilar machines to exchange information within one universal system With the ability to communicate the dissimilar machines act as a team The information that exists in one system can be reused without being reentered via keyboard or disk into another separate system A universal system for the integration and exchange
105. e of military needs in World War II the science of electronic data processing made giant strides forward In 1944 Harvard University developed a computing system known as the Automatic Sequence Controlled Calculator After the initial design and construction several improved models were built 1 2 Meanwhile at the University of Pennsylvania a second system was being developed This system completed in 1946 was named ENIAC Electronic Numerical Integrator and Computer ENIAC employed 18 000 vacuum tubes in its circuitry and in spite of these bulky hot tubes it worked quite successfully The first problem assigned to ENIAC was a calculation in nuclear physics that would have taken 100 human years to solve by conventional methods The ENIAC solved the problem in 2 weeks only 2 hours of which were actually spent on the calculation The remainder of the time was spent checking the results and operational details All modern computers have their basics in these two early developments conducted at Harvard University and University of Pennsylvania In 1950 the UNIVAC I was developed This machine was usually regarded as the most successful electronic data processor of its day An outstanding feature of the UNIVAC I was that it checked its own results in each step of a problem thus eliminating the need to run the problems more than once to ensure accuracy During the first outbreak of publicity about computers especially when the UNIVAC predicte
106. e problem as a whole 3 One step after another in specified order 4 step after another in random order 3 43 What is the step called in which you code a program that can be translated by a computer into a set of instructions it can execute Program booting 2 Program execution 3 Program logic 4 Program coding QUESTION 3 44 IS TO BE JUDGED TRUE OR FALSE 3 44 It is important to remember program coding is the first step of programming 1 True 2 False 3 45 Before sitting down to code the computer instructions to solve a problem you should complete which of the following activities 1 course in computer operation 2 Acourse in mathematics 3 Planning and coding 4 Planning and preparation 3 46 What is the fundamental element in program preparation 1 Subject 2 Predicate 3 Computer 4 Instruction 3 47 The first part of a computer instruction which answers the question what is known by which of the following terms Operation only Command only Command or operation Operand rs 3 48 3 49 3 52 The second specific part of the predicate in a computer instruction known as the operand in general answers what question 1 Who 2 What 3 When 4 Where What part of the program must the programmer prepare according to the format required by the language and the computer to be used 1 Documentation 2 Implementation 3 Instructions 4 Length To copy
107. e programmed and then in accordance with these instructions it executes the following procedures 1 Locates the parameters constants and such other data as may be necessary for problem solution 2 Transfers the parameters and data to the point of manipulation 3 8 3 Manipulates the parameters and data in accordance with certain rules of logic 4 Stores the results of such manipulations in a specific location 5 Provides the operator user with a useful output Even in a program of elementary character such as the one above this would involve breaking each of the steps down into a series of machine operations Then these instructions parameters and the data necessary for problem solution must be translated into a language or code that the computer can accept Next we ll provide an introduction to the problem solving concepts and flow charting necessary to develop a program OVERVIEW OF PROGRAMMING Before learning to program in any language it is helpful to establish some context for the productive part of the entire programming effort This context comprises the understanding and agreement that there are four fundamental and discrete steps involved in solving a problem on a computer The four steps are as follows 1 State analyze and define the problem 2 Develop the program logic and prepare a program flowchart or decision table 3 Code the program prepare the code in machine readable form prepare test data and perfor
108. e storage capacity of an address into a computer Q 23 What is another name for computers designed to be character oriented or character addressable Q 24 Which computer has the faster calculating speeds the variable word length or the fixed word length Q 25 What is the normal organization of data recorded on magnetic storage media Q 26 What is a file STORAGE ACCESS METHODS How data files are stored in secondary storage varies with the types of media and devices you are using Data files may be stored on or in sequential access storage direct access storage or random access storage SEQUENTIAL ACCESS STORAGE Punched cards paper tape and magnetic tape are examples of sequential access storage media When operating in a sequential environment a particular record can be read only by first reading all the records that come before it in the file When you store a file on tape the 125th record cannot be read until the 124 records in front of it are read The records are read in sequence You cannot read just any record at random This is also true when reading punched cards or paper tape DIRECT ACCESS STORAGE Direct access storage allows you to access the 125th record without first having to read the 124 records in front of it Magnetic disks and drums are examples of direct access storage media Data can be obtained quickly from anywhere on the media However the amount of time it takes to access a record is dependent to som
109. e strung together on a screen of wire to form what is called a core plane fig 4 8 view A As you may know each core can store one binary bit 0 or 1 of data A core is magnetized by current flowing through the wires on which the core is strung Hence a core magnetized in one direction represents a binary 0 and when magnetized in the opposite direction a binary 1 It is the direction that the core is magnetized that determines whether it contains a binary 0 binary 1 refer to fig 4 8 view B These core planes look very much like small window screens and are arranged vertically to represent data as shown in figure 4 8 view C In looking at this figure you will notice that nine planes are needed to code in 8 bit EBCDIC The ninth plane provides for a parity check bit Figure 4 8 view C shows DP 3 in EBCDIC code even parity m e n T z os E eI Qu UE 52 ee ESO 8 ONE OF MANY CORE PLANES THAT MAKE UP PRIMARY STORAGE Figure 4 8A Core storage with DP 3 represented using 8 bit EBCDIC code MAGNETIC SUBRRENT CURRENT IS CORE REMAINS CURRENT IS APPLIED THE MAGNETIZED AFTER REVERSED THE CORE IS CURRENT STOPS CORE REVERSES MAGNETIZED ITS MAGNETIC STATE B THE DIFFERENT STATES OF AMAGNETIC CORE Figure 4 8B Core storage with DP 3 represented using 8 bit EBCDIC code VERTICAL CORE PLANES NUMERIC BITS C DP 3 AS REPRESENTED IN PRIMARY STORAGE USING EVEN PARITY Figu
110. e will explain yet another way to classify internal primary or main storage This is by the different kinds of memories used within the cpu read only memory random access memory programmable read only memory and erasable programmable read only memory READ ONLY MEMORY ROM In most computers it is useful to have often used instructions such as those used to bootstrap initial system load the computer or other specialized programs permanently stored inside the computer Memory that enables us to do this without the programs and data being lost even when the computer is powered down is called read only memory Only the computer manufacturer can provide these programs in ROM and once done they cannot be changed Consequently you cannot put any of your own data or programs in ROM Many complex functions such as routines to extract square roots translators for programming languages and operating systems can be placed in ROM memory Since these instructions are hard wired permanent they can be performed quickly and accurately Another advantage of ROM is 2 7 that your computer facility can order programs tailored for its needs and have them permanently installed in ROM by the manufacturer Such programs are called microprograms or firmware RANDOM ACCESS MEMORY RAM Another kind of memory used inside computers is called random access memory RAM or read write memory RAM memory is rather like a blackboard on which you can scribble
111. ed you must be enrolled in the course with the Nonresident Training Course Administration Branch at the Naval Education and Training Professional Development and Technology Center NETPDTC Following enrollment there are two ways of having your assignments graded 1 use the Internet to submit your assignments as you complete them or 2 send all the assignments at one time by mail to NETPDTC Grading on the Internet Internet grading are Advantages to e you may submit your answers as soon as you complete an assignment and e you get your results faster usually by the next working day approximately 24 hours In addition to receiving grade results for each assignment you will receive course completion confirmation once you have completed all the vii assignments To submit answers via the Internet go to your assignment http courses cnet navy mil Grading by Mail When you submit answer sheets by mail send all of your assignments at one time Do NOT submit individual answer sheets for grading Mail all of your assignments in an envelope which you either provide yourself or obtain from your nearest Educational Services Officer ESO Submit answer sheets to COMMANDING OFFICER NETPDTC N331 6490 SAUFLEY FIELD ROAD PENSACOLA FL 32559 5000 Answer Sheets All courses include one scannable answer sheet for each assignment These answer sheets are preprinted with your SSN name assignment number and cour
112. edical and dental data are all to be added to SNAP systems The SNAP concept is to take the power of the modern computer the ability to process information and put that power in the hands of the work center sailors The sailors can use the system to reduce the labor associated with the paperwork function User terminals are placed in the different work centers for use by the work center supervisor Each work center has a different access code This access code or password prevents unauthorized entry into the main computer s program Different levels of entry are also defined The levels depend on a work center s need Information stored in the computer for a typical work center normally has the following items that can be updated by the work center supervisor COSAL coordinated onboard ship shore allowance list is a listing of the repair parts that are allowed to be kept onboard ship at all times APL allowance parts 1 16 list is the reference for stock numbers part numbers and quantity allowed onboard for a specific system EIC equipment identification code identifies a system sub system or equipment SHIP S FORCE WORK LIST is a listing of all work to be performed by a certain work center during a given time period CSMP current ship s maintenance projects provides shipboard maintenance managers with a consolidated listing of deferred maintenance to manage and control its accomplishment These are but a few of the uses of SNAP II that
113. eie anes 2 1 MEC E 3 1 4 Data Representation and Communications eese rennen 4 1 APPENDIX GlOSSaLy E P AI 1 M Listen oido 1 INDEX tet Ep Jack INDEX 1 iii NAVY ELECTRICITY AND ELECTRONICS TRAINING SERIES The Navy Electricity and Electronics Training Series NEETS was developed for use by personnel in many electrical and electronic related Navy ratings Written by and with the advice of senior technicians in these ratings this series provides beginners with fundamental electrical and electronic concepts through self study The presentation of this series is not oriented to any specific rating structure but is divided into modules containing related information organized into traditional paths of instruction The series is designed to give small amounts of information that can be easily digested before advancing further into the more complex material For a student just becoming acquainted with electricity or electronics it is highly recommended that the modules be studied in their suggested sequence While there is a listing of NEETS by module title the following brief descriptions give a quick overview of how the individual modules flow together Module 1 ntroduction to Matter Energy and Direct Current introduces the course with a short history of electricity and elect
114. ending sequence Most sort programs also allow you to sort in reverse order This is called descending sequence In EBCDIC it is 9 0 Z A then special characters To sort a data file you must tell the sort program what data field or fields to sort on These fields are called sort or sorting keys In our example the last name is the major sort key and the first name is the minor sort key Sorting is needed in many applications For example for mailing we need addresses in ZIP Code order personnel records may be kept in service number order and inventory records may be kept in stock number order We could go on and on Because many of our files are large sorting is very time consuming and it is one of the processes most used on computer systems As a user you will become very familiar with this process Sort merge programs usually have phases First they initialize read the parameters produce the program code for the sort allocate the memory space and set up other functions The sort merge program then reads in as many input data records as the memory space allocated can hold arranges sorts them in sequence and writes them out to an intermediate sort work file It continues reading input sorting and writing intermediate sort work files until all the input is processed It then merges combines the ordered intermediate sort work files to produce one output file in the sequence specified The merging process can be accomplished with le
115. ensure that any stored data lost can be recovered Q 59 The most common method of creating a backup for a microcomputer is what Q 60 Other than disk what is another media used for backup files SUMMARY This chapter has presented information on the history and classification of computers It introduced you to electronic digital computers their uses and operation The information that follows summarizes the important points of this chapter Early computers were MECHANICAL or ELECTROMECHANICAL ELECTRONIC COMPUTERS came into use in the 1940s ANALOG COMPUTERS are special purpose computers designed to measure continuous electrical or physical conditions DIGITAL COMPUTERS are special or general purpose computers designed to perform arithmetic and logic functions on separate discrete data They are generally used for business and scientific data processing Digital computers have evolved through four generations vacuum tubes transistors miniaturized circuits and integrated circuits WORD PROCESSING is one of the most widespread uses of desktop computers ACCOUNTING AND RECORDKEEPING are also major uses of computers Included are order entry inventory control accounts receivable accounts payable general ledger and payroll The Navy s SHIPBOARD NON TACTICAL ADP PROGRAM SNAP consists of computers used by work center supervisors for logistic and administrative support This system expedites the storage and retrieval of informat
116. er second produces a smooth flicker free raster and corresponding display on the screen PICTURE ELEMENTS The actual display of data results from the use of picture elements A picture element is a variable dot of light derived from video signals input to the display monitor The picture elements often called pixels or pels are contained in the horizontal scan lines crossing the face of the crt screen The horizontal and vertical sweeps are continuous and repetitive in nature Pictures with alphanumeric characters and graphics can be created and displayed by varying the intensity or brightness of the picture element dots This is done in conjunction with the phosphor coating on the face of the crt The number of picture elements in each horizontal line varies from device to device The actual number of picture elements is dependent on the frequency bandwidth of the video monitor the number of characters to be displayed on a line and the physical size of the screen 2 29 Each picture element is addressable by a row and column address Picture elements are numbered from left to right on each horizontal line column number Each horizontal line has a row number Picture elements at a minimum will have off blanked or on full intensity states Many display devices have the capability to display picture elements at varying degrees of intensity for the display of graphics Characters are assembled on the screen in much the same way as a do
117. er ways to do it Contrary to popular belief digital computers are not a new idea The abacus is a manually operated digital computer used in ancient civilizations and used to this day in the Orient see fig 1 1 For those who consider the abacus outdated in a contest between a person using a modern calculator and a person using an abacus the person using the abacus won 0 2 3 2 15 0 78920 Figure 1 1 Abacus The first mechanical adding machine calculator was invented by Blaise Pascal French in 1642 Twenty years later an Englishman Sir Samuel Morland developed a more compact device that could multiply add and subtract In 1682 Wilhelm Liebnitz German perfected a machine that could perform all the basic operations addition subtraction division and multiplication as well as extract the square root Liebnitz s principles are still in use today in our modern electronic digital computers As early as 1919 electronics entered the scene An article by W H Eccles and F W Jordan described an electronic trigger circuit that could be used for automatic counting It was the ECCLES JORDAN multivibrator which was a little ahead of its time because a trigger circuit is one of many components required to make an electronic digital computer Modern digital computers use these circuits known as flip flops to store information perform arithmetic operations and control the timing sequences within the computer Under the pressur
118. ervices all channels on the drum In this case the head moves back and forth or up and down over the surface of the drum as required Other drums using multiple read write heads have one principal advantage over drums with the single head type Since one read write head is assigned to each channel no read write head movement is required That is the time required for head positioning is zero The only significant time required when reading or writing 1s the rotational delay that occurs in reaching a desired record location To give you some idea of speed and storage capacities some high speed drums are capable of transferring over one million characters of data per second which is roughly equivalent to reading a stack 2 17 of punched cards 8 feet high in one second The storage capacities of magnetic drums range from 20 million to more than 150 000 million characters or bytes of data Q 26 Why are disk storage devices popular Q 27 How is data stored on all disks Q 28 What precedes each record on a disk Q 29 How is the storage capacity of a disk determined Q 30 What two ways can data be physically organized on a disk pack Q 31 The amount of data that can be stored on a linear inch of tape is known by what term Q 32 The length of tape between BOT and EOT is referred to by what term Q 33 How does a magnetic drum differ from a magnetic disk Q 34 Tracks on each channel of a magnetic drum are grouped into what INPUT
119. es and Power Supplies is similar to module 6 but it is in reference to solid state devices Module 8 Introduction to Amplifiers covers amplifiers Module 9 Introduction to Wave Generation and Wave Shaping Circuits discusses wave generation and wave shaping circuits Module 10 Introduction to Wave Propagation Transmission Lines and Antennas presents the characteristics of wave propagation transmission lines and antennas iv Module 11 Microwave Principles explains microwave oscillators amplifiers and waveguides Module 12 Modulation Principles discusses the principles of modulation Module 13 Introduction to Number Systems and Logic Circuits presents the fundamental concepts of number systems Boolean algebra and logic circuits all of which pertain to digital computers Module 14 Introduction to Microelectronics covers microelectronics technology and miniature and microminiature circuit repair Module 15 Principles of Synchros Servos and Gyros provides the basic principles operations functions and applications of synchro servo and gyro mechanisms Module 16 Introduction to Test Equipment is an introduction to some of the more commonly used test equipments and their applications Module 17 Radio Frequency Communications Principles presents the fundamentals of a radio frequency communications system Module 18 Radar Principles covers the fundamentals of a radar system Module 19 The Technicia
120. essing and take action based on the result Q 7 In the arithmetic logic section data is returned to what section after processing Q 8 What is the process by which instructions and data are read into a computer TYPES OF INTERNAL STORAGE You already know that the internal storage section is the holding area in which instructions and data are kept For the control section to control and coordinate all processing activity it must be able to locate each instruction and data item in storage About now you are probably wondering how the control section 1s able to find these instructions and data items To understand this let s look at storage as nothing more than a collection of mailboxes Each mailbox has a unique address and represents a location in memory as shown in figure 2 2 Like the mail in your mailbox the contents of a storage location can change but the number on your mailbox or memory address always remains the same In this manner a particular program instruction or data item that 1s held in storage can be located by knowing its address Some computers can address each character of data in memory directly Others address computer words which contain a group of characters at a single address Each computer word contains a group of characters at a 2 4 single address Some of the more common types of internal storage media used in today s computers are as follows magnetic core semiconductor and bubble PRIMARY STORAGE 1004 10
121. f the following is NOT a basic 3 34 characteristic of a computer 1 It needs commands It needs specifically defined operations 3 Itcan think 4 It can understand instructions only in an acceptable form How many fundamental and discrete steps are involved in solving a problem 3 35 on a computer 1 Five 2 Two 3 Three 4 Four 3 36 In the advance planning phase of programming what are the first two steps Program coding and machine readable coding preparation 2 Problem understanding definition and flowcharting 3 Test data preparation and test run performance 4 Documentation completion and operator procedures preparation Which of the following is NOT part of defining every aspect of a problem The method of pictorially representing a step by step solution to a problem before computer instructions are written to produce the desired results is called what 1 Flowcharting 2 Constructing 3 Documenting 4 Debugging What two types of flowcharts are there System and programming System and data Processing and programming Processing and data Arp What are the four basic tools used in flowcharting 1 Advanced symbols graphic symbols flowcharting template and flowcharting worksheet 2 Fundamental symbols graphic symbols flowcharting template and flowcharting worksheet 3 Fundamental symbols mathematical symbols flowcharting symbols and flowcharting worksheet 4 Fundame
122. forecast crop statistics and believe it or not design other computers Word Processing Remember these words were typed into a desktop computer Word processing is among the most common applications for personal computers If you have not discovered the advantages of computer writing it s time to visit a computer dealer for a personalized demonstration None of this work could be performed by a computer without first instructing the computer how to do it by means of a list of instructions called a program The instructions in the program must be written in one of the languages the computer understands The most popular generic term for computer programs is software this is covered in chapter 3 Hardware covered in chapter 2 of course refers to the computer and related equipment It is easy to say that both computer hardware and software are interdependent because neither can perform useful work without the other Digital computers may be either special or general purpose ACCURACY OF COMPUTERS The fundamental difference between analog and digital computers is that digital computers deal with discrete quantities such as beads on an abacus notches on a toothed wheel or electrical pulses while analog computers deal with continuous physical variables such as electrical voltages or mechanical shaft rotations Computation with analog computers depends on the relation of information to a measurement 1 7 of some physical quantity For examp
123. from a keyboard The most commonly used input devices in this category are magnetic tape units magnetic disk drive units and floppy disk drive units Output information is also made available in three forms 1 Displayed information codes numbers words or symbols presented on a display device like a cathode ray screen 2 18 2 Control signals information that operates a control device such as a lever aileron or actuator 3 Recordings information that is stored in a machine language or human language on tapes disks or printed media Devices that display store or read information include magnetic tape units magnetic disk drive units floppy disk drive units printers and display devices MAGNETIC TAPE UNITS INPUT OUTPUT The purpose of any magnetic tape unit drive or device is to write data on or read data from a magnetic tape fig 2 17 Tape stores data in a sequential manner In sequential processing the computer must begin searching at the beginning and check each record until the desired data is found Like a tape cassette with recorded music to play the fifth song recorded you must play or fast forward the tape past the first four songs before you can play the fifth Figure 2 17 Magnetic tape unit Two reels are used tape moves from a supply reel to a take up reel both are mounted on hubs Figure 2 18 shows the basic tape drive mechanism The magnetic oxide coated side of the tape passes directly over
124. he expense of what capabilities Q 12 All analog computers are what type of computers Q 13 What are analog computers designed to measure Q 14 Early analog computers were what type of devices Q 15 What are computers called that combine the functions of both analog and digital computers Q 16 Digital computers are generally used for what purposes Q 17 What is the fundamental difference between analog and digital computers Q 18 How is the accuracy of an analog computer restricted 1 9 Q 19 A constant represented by a voltage can be read to what decimal place Q 20 The accuracy of a digital computer is governed by what factor Q 21 Ina digital computer what does the number of decimal places in the constant depend on Q 22 You will most likely be working with what type of computer DIGITAL COMPUTER GENERATIONS In the electronic computer world we measure technological advancement by generations A specific system is said to belong to a specific generation Each generation indicates a significant change in computer design The UNIVAC I represents the first generation Currently we are moving toward the fourth generation FIRST GENERATION The computers of the first generation 1951 1958 were physically very large machines characterized by the vacuum tube fig 1 6 Because they used vacuum tubes they were very unreliable required a lot of power to run and produced so much heat that adequate air conditioning was criti
125. he records printed in alphabetical order by last name The software also provides routines so you can easily add delete and change records Last Name MOORE First Name Lawrence Rates SSN 213 08 3102 Reporting Date 12 NOV 87 Phone NO 904 452 4781 Figure 3 9A Data management example PROMPTS IN BOLD AND DATA IN ITALICS 324 REPORTING 123 07 0736 15 William 219 347 3261 Figure 3 9B Data management example SAMPLE PRINTED REPORT SORTED BY LAST NAME You can also generate reports by specifying what records to use what fields to print where to print the fields and which data fields if any need to be combined For example your supply officer wants to know the value of the inventory You can specify that the extended price is to be calculated by multiplying the item quantity by the unit price and that the extended prices are to be totaled INVENTORY VALUE ITEM QUANTITY UNIT EXTENDED PRICE PRICE 4 Swabs 77 55 139 50 36 Foxails 36 185 66 60 TOTAL o 283 65 You can also specify the information to be used in report and column headings While the data management programs on micros are not as sophisticated as the data base management systems on mainframes and minis they do provide an extremely useful capability in offices or aboard ship SPREADSHEETS Spreadsheets are tables of rows and columns of numbers Figure 3 10 shows an example Spreadsheet processors allow you
126. hear used for semiconductor memory chips is integrated circuits ICs Developments in technology have led to large scale integration LSI which means that more and more circuits can be squeezed onto the same silicon chip Companies are even manufacturing very large scale integrated circuits VLSI which means even further miniaturization 570421 Figure 2 4 semiconductor memory chip integrated circuit Some of the advantages of semiconductor storage are fast internal processing speeds high reliability low power consumption high density many circuits and low cost However there is a drawback to this type of storage It is volatile which means all data in memory is lost when the power supply 1s removed Should the power on your computer fail and you have no backup power supply all the stored data is lost This is not the case with magnetic core storage Core storage is nonvolatile This means the data 1s retained even if there is a power failure or breakdown since the cores store data in the form of magnetic charges rather than electric current BUBBLE STORAGE One of the latest technological developments in storage media is the introduction of bubble memory Bubble memory consists of a very thin crystal made of semiconductor material The molecules of this special crystal act as tiny magnets fig 2 5 The polarity of these molecules or magnetic domains can be switched in an opposite direction by passing a current through
127. hem out when you are finished with them SECONDARY STORAGE is the memory outside the main body of the computer cpu where we store programs and data for future use MAGNETIC TAPE is a sequential access storage device MAGNETIC DISK is a direct access storage device INPUT OUTPUT DEVICES are the means by which the computer communicates with the outside world These include magnetic tape units magnetic disk drive units floppy disk drive units printers daisy wheel dot matrix ink jet and laser and display devices raster scan crt and flat panel 2 33 4 1 4 2 4 3 4 4 4 5 4 6 4 7 8 9 A 10 4 11 4 12 4 13 4 14 4 15 4 16 4 17 4 18 4 19 4 20 4 21 4 22 4 23 4 24 4 25 A 26 A 27 A 28 ANSWERS TO QUESTIONS Q1 AND Q49 The central processing unit Three Control section internal storage section and arithmetic logic section A telephone exchange Transfer arithmetic logic and control Logic Internal storage Loading Tiny doughnut shaped rings made of ferrite iron Hundreds of thousands of tiny electronic circuits etched on a silicon chip Integrated circuits All data in memory is lost when the power source is removed Nonvolatile magnetic core storage and bubble memory are examples A very thin crystal made of semiconductor material By passing a current through a control circuit imprinted on top of the crystal The data is still present after being read Read only memo
128. her programs use the computer A digital computer uses one central set of programs called the operating system to manage execution of other programs and to perform common functions like read write or print Other programs or you the user can order the operating system to perform these common functions These orders are called system calls when other programs use them or simply commands when you put them through the keyboard First you must load the operating system into the computer so we and our programs can use the computer Remember in our example we have a desktop computer with two floppy disk drives named A and B Booting the System Each desktop computer has a built in program called bootstrap loader When you turn the computer on this program tries to load or boot an external operating system from disk usually from drive A into the computer s internal memory Disk drive B is usually used for data file disks The term boot comes from the idea of pulling yourself up by your bootstraps The computer loads a little program from the disk that tells it how to load a second bigger program the operating system The operating system then tells it how to load another program an applications program or utility program to perform a specific job or function The first thing you need to learn about using a computer is that computers and their programs are very particular They require complete accuracy and attention to detail on your pa
129. hich you want the copy into drive B Be sure it is formatted with the track and sector information so it is ready to receive data Also be sure the disk is not write protected On a 5 1 4 inch floppy disk that means the write protect notch is uncovered Following the A gt type COPY MASTER DOC B and press RETURN The system will copy the file and give it the same name Next you might want to display the directory on drive B to see that the file was copied You can do this by entering DIR B following the A gt prompt To delete the file on the floppy disk in drive A type DEL MASTER DOC following the A gt prompt on the screen and press RETURN You probably noticed each entry in the directory is followed by three characters These are called extensions and we use them to tell us the type of file we are working with For example BAK Means backup file BAS Means BASIC source program TMP Means temporary file Means ASCII document file BIN Means binary file and so on Other typical built in operating system commands you can use might include 3 3 RENAME to change the name of a file DISKCOPY to copy a whole floppy disk FORMAT to initialize a floppy disk get it ready to receive data and programs from the system TIME to display or set the time You will learn to use these and many other system commands as you operate a specific computer We won t go into any more det
130. hile MS DOS uses the command COPY Remember the first thing you need to do is boot initial program load the system There are many ways this can be done Here is an example When you turn on the power a prompt may appear on the 3 2 screen You then insert the operating system floppy disk into the drive A Type a B for boot and press the RETURN key The operating system will load from the disk If you are using a system set up for automatic booting you won t have to type the B The system automatically loads the operating system when you insert the disk that contains it Some systems will then ask for date and time Enter these You will next see a prompt usually A gt or A The system is ready and drive A is assigned as your primary drive One thing you might want to do is to display the disk directory to see what is on the disk To do this enter DIR following the A gt This will list your files COMMAND COM CONFIGUR COM DATDBL DATDBL DOC FINANCE BAS MASTER DOC It may also give you file size and the date and time of the file Let s take an example Let s say you are to copy the file MASTER DOC from the floppy disk in drive A to the floppy disk in drive B and then delete the file on the floppy disk in drive A You have just displayed the directory of the floppy disk in drive A Check to see that the file you want is on the floppy disk in drive A It is You then insert the floppy disk on w
131. ice to another card to tape tape to tape tape to disk and so on SORT MERGE PROGRAMS arrange data records in a predefined sequence or order and are capable of combining two or more ordered files into one file REPORT PROGRAM GENERATORS are used to generate programs to print detail and summary reports of data files 3 27 PROGRAMMING LANGUAGES are the means by which human computer communication is achieved They are used to write the instructions to tell the computer what to do to solve a given problem A MACHINE LANGUAGE uses a string of numbers that represent the instruction codes and operand addresses to tell the computer what to do SYMBOLIC LANGUAGES improved the program preparation process by substituting letter symbols mnemonic codes for basic machine language instruction codes A PROCEDURE ORIENTED LANGUAGE is a programming language oriented toward a specific class of processing problems Examples are BASIC COBOL and FORTRAN PROGRAMMING is the process of planning and coding the computer instructions to solve a problem FLOWCHARTING is one method of pictorially representing a procedural step by step solution to a problem before you actually start to write the computer instructions required to produce the desired results PACKAGED SOFTWARE is designed for specific classes of applications Examples are word processing spreadsheets data management and graphics These off the shelf programs are written by the manufacture
132. icular application or perform a particular function Instructions The instruction 1s the fundamental element in program preparation Like a sentence an instruction consists of a subject and a predicate However the subject is usually not specifically mentioned rather it is some implied part of the computer system directed to execute the command that is given For example the chief tells a sailor to dump the trash The sailor will interpret this instruction correctly even though the subject you is omitted Similarly if the computer is told to ADD 1234 the control section may interpret this to mean that the arithmetic logic section is to add the contents of address 1234 to the contents of the accumulator a register in which the result of an operation is formed In addition to an implied subject every computer instruction has an explicit predicate consisting of at least two parts The first part 1s referred to as the command or operation it answers the question what It tells the computer what operation it is to perform 1 e read print input Each machine has a limited number of built in operations that it is capable of executing An operation code is used to communicate the programmer s intent to the computer The second specific part of the predicate known as the operand names the object of the operation In general the operand answers the question where Operands may indicate the following 1 The location where data to
133. in front of it which of the followin types of storage is being used 1 Reading access 2 Direct access 3 Sequential access 4 Processing access Which of the following is an example of random access storage 1 Disk 2 Thin film 3 Paper tape 4 Magnetic tape Any system composed of one or more computers and terminals is the definition for what Network ADP system Computer system Supply system AUN A network that consists of various machines linked together within a building or adjacent buildings is what type Wide area Linked area Local area Narrow area AUN 4 41 4 42 4 43 4 44 4 45 4 46 25 When dissimilar machines have the ability to communicate they act in which of the following ways 1 Human 2 As a team 3 Individuall 4 Against c ch other F d or local area networks what two esigns are used Broadband and bandpass 2 and bandpass 3 Broadbase and baseband 4 Broadband and baseband The communications channel that uses the basic frequency band of radio waves and a coaxial cable is what type 1 Broadband 2 3 Baseband 4 Bandpass The transmission of voice as well as data and text can be handled by what type of communications channels 1 Broadband 2 3 Baseband 4 Bandpass Wide area networks are sometimes referred to as which of the following networks 1 Local 2 Gl
134. in mechanical electromechanical and electronic computers special purpose and general purpose computers and analog and digital computers MECHANICAL COMPUTERS Mechanical or analog computers are devices used for the computation of mathematical problems They are made up of components such as integrators sliding racks cams gears springs and driveshafts Figure 1 2 shows a typical mechanical computer used by the Navy These computers are analog in nature and their physical size depends on the number of functions the computer has to perform In an analog computer a continuing input will give a constantly updated output This being perfect for target information the Navy uses these analog computers primarily for gun fire control As systems for naval weapons became more and more complex the need for a different computer was apparent The functions that had to be performed had increased the size of the computer to an unreasonable scale 1 3 Figure 1 2 Bulkhead type mechanical computer ELECTROMECHANICAL COMPUTERS Electromechanical computers came next and differ from mechanical computers in that they use electrical components to perform some of the calculations and to increase the accuracy Because the electrical components are smaller than their mechanical counterparts the size of the computer was reduced even though it performs more functions The components used to perform the calculations are devices such as synchros servos res
135. ingle data records we normally block records In figure 2 15 view B you will notice the tape is used more efficiently than the tape in figure 2 15 view A Blocking allows more data to be stored on a reel of tape During reading the record begins with the first character sensed following an interrecord or interblock gap and continues until the next gap is reached All input records read are internally stored in accordance with the amount of storage area set aside by the applications program Magnetic tape as a storage media offers several useful features We can store large amounts of data in a variety of convenient package sizes open reels cartridges or cassettes Magnetic tapes are easily interchangeable between similar tape units of different computer systems and tapes are less prone to damage than other types of storage media MAGNETIC DRUM Like the magnetic disk the magnetic drum is another example of a direct access storage device Although the magnetic drum was once used as main or primary storage it is now used as secondary or auxiliary storage Unlike some disk packs the magnetic drum cannot be physically removed The drum is permanently mounted in the device Magnetic drum storage devices consist of either a hollow cylinder thus the name drum or a solid cylinder that rotates at a constant velocity from 600 to 6 000 rpm The outer surface is coated with an iron oxide material capable of being magnetized 2 16 A
136. ion the Navy has about its ships A DESKTOP PERSONAL COMPUTER is a microcomputer with at least a display screen keyboard floppy disk drive and printer It may also have additional devices such as a second floppy or a hard disk drive An OPERATING SYSTEM is loaded into the computer to let you and other programs use the computer It also provides common functions like read write and print You can direct the computer to run an APPLICATION PROGRAM by telling the operating system the name of program to run Common application programs are word processing accounting and recordkeeping You will probably be using FLOPPY DISKS for data storage and backup To ensure you don t damage a disk use care in handling labeling and storing the disks 1 22 A 2 4 3 4 4 4 5 4 6 4 7 4 6 4 9 4 10 4 11 4 12 4 13 4 14 4 15 4 16 4 17 4 18 4 19 4 20 4 21 4 22 4 23 4 24 4 25 4 26 ANSWERS TO QUESTIONS Q1 THROUGH Q60 Technology mechanical electromechanical electronic purpose special or general type of data they handle analog or digital cost physical size handheld to room size Analog Gun fire control Electromechanical computers use electrical components to perform some of the calculations Integrated circuits Special purpose Its design Lack of versatility To perform a wide variety of functions and operations By storing different programs in its internal storage Speed
137. ire what type of plane is formed 1 A wire plane 2 core plane 3 A screen plane 4 A magnetic plane 4 24 When core is magnetized what characteristic of magnetism 4 30 determines whether it contains a binary 0 or a binary 1 1 Amount 2 Duration 3 Direction 4 Saturation 4 25 The storage capacity of an address is designed and built 4 31 into the computer by which of the following people or organizations 1 Operator 2 Installer 3 Programmer 4 Manufacturer 4 26 Computers that are built to retrieve manipulate and store a fixed number of characters in 4 32 each address are said to be which of the following types of computers 1 Fixed bit length 2 Fixed word length 3 Fixed file length 4 Fixed number length 4 27 Computers that store a single character in each address 4 33 location are said to be which of the following types of computers 1 Variable addressable 2 Data addressable 3 Fixed addressable 4 Character addressable QUESTION 4 28 IS TO BE JUDGED TRUE OR FALSE 4 34 4 28 Fixed word length computers have slower calculating speeds than character addressable computers True 2 False 24 Flexible computers that are byte oriented can operate in either a fixed or variable word length mode by which of the following techniques 1 Proper program length 2 Proper program density 3 Proper program instructions 4 Proper program flexi
138. is recorded 3 Byagap in which the record is numbered 4 By a gap in which the operator s name is placed To increase the amount of data we can store on one track what technique can be used Records 2 Files 3 Disk address 4 Blocking 2 33 2 34 2 35 2 36 2 37 Designers were able to increase the data 2 38 density of a disk by increasing the number of tracks What code name was given to this technology 1 Computer 2 Winchester 3 Solid state 4 Colt 2 39 During reading and writing which of the following changes are achieved by reducing the distance of the read write heads over the disk surface 1 Data density can be improved and storage capacity decreased 2 Data density is lessened and storage capacity increased 3 Data density can be improved and 2 40 storage capacity increased 4 Data density is lessened and storage capacity decreased To physically organize data on diskettes what method is used The lengths of magnetic tapes used with computers have what range 1 From 400 to 1 000 feet 2 From 500 to 2 000 feet 3 From 600 to 3 000 feet 4 From 700 to 4 000 feet Magnetic tapes can be packaged in which of the following ways 2 42 1 Open reel only 2 Cartridge and cassette only 3 Open reel and cartridge only 4 Open reel cartridge and cassette 10 1 Records 2 Cylinder 2 41 3 Files 4 Sector By which of the following methods are magneti
139. is to be performed It is also active in initiating circuits that locate any information stored within the computer or in an auxiliary storage device and in moving this information to the point where the actual manipulation or modification is to be accomplished The four major types of instructions are 1 transfer 2 arithmetic 3 logic and 4 control Transfer instructions are those whose basic function is to transfer move data from one location to another Arithmetic instructions are those that combine two pieces of data to form a single piece of data using one of the arithmetic operations Logic instructions transform the digital computer into a system that is more than a high speed adding machine Using logic instructions the programmer may construct a program with any number of alternate sequences For example through the use of logic instructions a computer being used for maintenance inventory will have one sequence to follow if the number of a given item on hand is greater than the order amount and another sequence if it is smaller The choice of which sequence to use will be made by the control section under the influence of the logic instruction Logic instructions thereby provide the computer with the ability to make decisions based on the results of previously generated data That is the logic instructions permit the computer to select the proper program sequence to be executed from among the alternatives provided by the programmer
140. isplay of alphanumeric data and graphics Two 525 Pixels or pels The number of horizontal scan lines used Reduce the depth of the crt display caused by the length of the tube An external light source called a backlight 2 35 CHAPTER 3 SOFTWARE LEARNING OBJECTIVES Upon completion of this chapter you will be able to do the following 1 Recognize and compare the different types and functions of operating systems 2 Identify the types of utilities and explain their functions 3 Describe the different types and functions of programming languages 4 Explain the steps necessary to develop a program and describe the tools used 5 Compare and describe the types and functions of applications packages INTRODUCTION Up to now we have been discussing computer OPERATIONAL CONCEPTS and HARDWARE the computer and its peripheral devices and how these devices work and communicate with each other What about this thing called SOFTWARE Do we really need it We most certainly do Software plays a major role in computer data processing For example without software the computer could not perform simple addition It s the software that makes everything happen Or putting it another way software brings the computer to life You already know it takes a program to make the computer function You load an operating system into the computer to manage the computer s resources and operations You give job information to the operating system t
141. ital computer the number of decimal places in the constant could be many depending on the design of the computer processing unit The digital computer is therefore capable of higher precision and accuracy However a computer regardless of its accuracy would do you no good if the wrong one were chosen for a given task Most of the computer systems you will work with will be general purpose digital computers The remainder of this module will be about general purpose digital computers Q 1 How are computers classified Q 2 Mechanical computers are considered to be of what type Q 3 The Navy uses analog computers primarily for what purpose Q 4 How do electromechanical computers differ from the mechanical computers Q 5 In electronic computers vacuum tubes were replaced by transistors and transistors have been replaced by what device 6 A computer that is designed to perform a specific operation and usually satisfies the needs of a particular type of problem is said to be what type of computer 7 Rather than using a stored program a special purpose computer s applicability to a particular 8 problem is function of what Q 8 What is a drawback to the special purpose computer Q 9 A general purpose computer is designed for what purpose Q 10 How is a general purpose computer able to perform different operations Q 11 Ina general purpose computer the ability to perform a wide variety of operations is achieved at t
142. k inserted incorrectly in drive 3 Lock handle on drive A not lowered 4 Each of the above A display similar to this A gt means what in computer terminology 1 device error 2 No system 3 A prompt 4 Run again 1 42 1 43 1 44 1 45 1 46 What does it mean when the computer displays a prompt on the screen 1 The computer has made an error There is no system in the computer 3 You need to stop putting information into the computer 4 Youcan tell the computer what to do next To tell the operating system what program to run you should take which of the following actions following the operating system prompt A gt Type help Reboot the computer Press the execute key Type the program name Online HELP screens serve what purpose 1 Display the contents of memory Display the operating system directory 3 Tell the operator how to perform given function 4 Stop computer processing so the operator can read the instruction manual Floppy disks provide which of the following functions l Store data 2 Perform arithmetic operations 3 Provide alternate power to the computer 4 Check the accuracy of computer operations Touching the exposed area seen through the timing hole and the read write slots on a floppy disk can do what if anything to the data in that area 1 Ruin it 2 Add to it 3 Move it 4 Nothing 1 47 1 48 1 49 1 50 1 51 What maximum
143. lace in the same document or even move it to a different document Word processing is particularly useful for text documents that are repetitive or that require a lot of revisions It saves a lot of rekeying Wordprocessing software saves keystrokes It helps you create store retrieve edit and print text You can insert delete and rearrange text You can also use special features like spelling checkers mailing lists document compilation and communications Figure 3 8 Word processing example Other features and software often available with a word processing software package include spelling checkers mailing list programs document compilation programs and communications programs Spelling checker software helps find misspelled words but not misused words It scans the text matching each word against a dictionary of words If the word 1s not found in the dictionary the system flags the word You check it If it is misspelled you can correct it You will still have to proofread the document to see that everything was keyed and that the words are used correctly 3 23 Mailing list programs are for maintaining name and address files They often include a capability to individualize letters and reports by inserting names words or phrases to personalize them Document compilation programs are useful when you have standard paragraphs of information that you need to combine in different ways for various purposes For exampl
144. le you can determine the number of boards in a picket fence by either a digital or an analog system as follows In the digital method fig 1 5 view A you use an adding machine and count the boards one by one In the analog method fig 1 5 view B you draw a string marked off in inches for the width of each board including the gap over the length of the fence then measure the length of the string The number of boards may then be determined by dividing the length of string by the number of inches per board 12 3 45 6 7 8 9 10 11121314 DIGITAL Figure 1 5A Digital computation STRING 10 5 ai 6 3 a BOARD STRING SCALE 6 WDE 10 5 LONG ye GAP BOARD GAP 3 WIDE 9 ANALOG 10 5X12 126 14 9 B Figure 1 5B Analog computation 1 8 The accuracy of an analog computer is restricted to the accuracy with which physical quantities can be sensed and displayed This in turn is related to the quality of the components used in constructing the computer for example the tolerance of electrical resistors or mechanical shafts and the quality of the output equipment In an analog computer for example if the constant is represented by a voltage it probably could be read only to the third decimal place On the other hand the accuracy of a digital computer is governed by the number of significant figures carried in the computations This in turn is determined by the computer s design In a dig
145. le track A track can hold one or more records A record is a set of related data treated as a unit The records on a track are separated by gaps in which no data is recorded and each of the records is preceded by a disk address This address indicates the unique position of the record on the track and is used to directly access the record Figure 2 9 shows a track on which five records have been recorded Because of the gaps and addresses the amount of data we can store on a track is reduced as the number of records per track is increased Records on disk can be blocked grouped together Only one disk address is needed 2 10 per block and as a result fewer gaps occur We can use the blocking technique to increase the amount of data we can store on one track gt Figure 2 9 records as they are written to disk on a single track The storage capacity of a disk depends on the bits per inch of track and the tracks per inch of surface Using Winchester technology the designers of disk drive units were able to increase the data density of a disk by increasing the number of tracks Winchester was the code name used by IBM during the development of this technology The designers originally planned to use dual disk drives to introduce the new concept Each drive was to have a storage capacity of 30 million characters and thus was expected to be a 30 30 Since that was the caliber of a famous rifle the new product was nick
146. lement in the top row or line and ending with the last picture element on the bottom row The picture elements are turned on and off at a high enough frequency that the human eye cannot detect the flicker of the off on off cycle The sequential scan used to light the picture elements is continuous and repetitive Once again the page memory must be changed to change the display Flat panel displays may be formatted or unformatted in the same manner as crt displays Q 35 What is the purpose of any magnetic tape unit Q 36 What are the major differences between magnetic tape units Q 37 Why is direct accessing of data a big advantage over the sequential accessing of data Q 38 What is a floppy disk Q 39 What are the three most common sizes of floppy disks Q 40 What output device expresses coded characters as hard copy paper documents Q 41 What four types of printers are commonly used with personal computers Q 42 What is the primary purpose of a keyboard Q 43 Raster scan or tv scan video monitors are used extensively for what purpose Q 44 How many fields make up a frame Q 45 A field is approximately how many horizontal lines 2 32 Q 46 What are picture elements often called Q 47 Vertical resolution depends on what Q 46 Flat panel displays are designed to reduce what problem of a crt display Q 49 What does the liquid crystal display require for computer applications SUMMARY Now that you have finished chap
147. lity for some element of ship s maintenance And for every rate recordkeeping has been a tough nut to turn an administrative chore that goes along with the work to be done but takes a back burner position to the physical maintenance of the ship and equipment Today aboard some ships and soon aboard most much of that hassle will be done with a SNAP 1 15 The Navy has looked at the paperwork blizzard of recordkeeping responsibility of the essential records and reports that must be generated and has offered relief to the fleet This is in the form of S N A P which stands for Shipboard Non Tactical ADP Program SNAP II is a modern shipboard computer system designed to support shipboard and intermediate level maintenance supply financial and administrative functions If this sounds confusing it really isn t for the systems are designed to be user friendly that 1s operating instructions are written in everyday English Figure 1 11 shows the AN UYK 62 V Data Processing Set This is the SNAP II computer and Its associated hardware WORD PROCESSIHG DISPLAY PRINTER PRINTER MAGHETIC COMPUTER TAPE UNIT PAPER TAPE READER PUNCH we M LINE PRINTER DATE TERMINAL HAND FED Ripa CARD READER Figure 1 11 AN UYK 62 V Data Processing Set SNAP Over the next 3 years new functions will be added to SNAP to support more of the ship s administrative workload Pay personnel food service ship s store PMS training m
148. longs together as a unit regardless of the physical size or storage location of the data unit of measurement approximately equal to one million and used to express the capacity of a computer memory 1M is about 1 000 000 units Memory size is usually measured in words or bytes MACHINE LANGUAGE Machine instructions in binary bit patterns that the central processing unit can execute directly without additional interpretation or translation MACHINE TAKE UP REEL A reel that remains on the tape drive and on which magnetic tape is wound during the processing of a tape MAGNETIC MEDIA Magnetic cards tapes disks drums cartridges and cassettes used to record data or information MAGNETIC TAPE A mass storage device in which information is stored on a plastic tape coated with a magnetic film The tape is wound on reels that are rotated by tape drives Information is stored and retrieved sequentially by magnetically sensitive read write heads MAINFRAME COMPUTERS This term is usually used to designate large scale computer systems although the precise definition of mainframe is the cpu and the control elements of any computer system MAIN STORAGE MEMORY See storage primary MASS STORAGE Any external storage medium magnetic tape disk drum and so on that supports and can be linked to the cpu s main memory in the computer When the power is turned off information in the mass storage is retained not lost
149. m debug and test runs 4 Complete the documentation and prepare operator procedures for implementation and production Figure 3 2 depicts the evolution of a program Programming can be complicated and advance preparation is required before you can actually start to write or code the program The first two steps problem understanding definition and flowcharting fall into the advance planning phase of programming It is important at this point to develop correct habits and procedures since this will prevent later difficulties in program preparation 3 9 PROBLEM DEFINITION TERMINAL FOR KEYING PROGRAMS FLOWCHART COMPUTER FOR ASSEMBLY COMPILATION DEBUGGING AND TESTING OBJECT PROGRAM OUTPUT PROGRAM LISTING Figure 3 2 Evolution of a program Whether you are working with a systems analyst a customer or solving a problem of your own it is extremely important that you have a thorough understanding of the problem Every aspect of the problem must be defined e What is the problem e What information or data is needed e Where and how will the information be obtained e What is the desired output Starting with only a portion of the information or an incomplete definition will result in having to constantly alter what has been done to accommodate the additional facts as they become available It is 3 10 easier and more efficient to begin programming after all of the necessary information is underst
150. magnetic drum differs from a magnetic disk in that the tracks in which the data is stored are assigned to channels located around the circumference of the drum as shown in figure 2 16 That is the channels form circular bands around the drum The coded representation of data in figure 2 16 is similar to that used on 9 track magnetic tape 8 bit code The basic functions of the read write heads are to place magnetized spots those little binary 0 s and 1 s on the drum during a writing operation and to sense these spots during a reading operation The read write heads of a drum perform in a manner similar to the read write heads of a magnetic tape unit or disk drive unit TRACKS C222228421 FIRST CHARACTER 111100116 101101000 111001110 911111001 200 CHARACTERS EBCDIC CHANNELS Figure 2 16 Magnetic drum The tracks on each channel are grouped into sectors as illustrated in figure 2 16 Does this sound familiar to you It sounds almost like the format used on disk packs when referring to tracks or cylinders and sectors As the drum rotates the reading or writing occurs when the specified sector of a given channel passes under the read write head for that channel Some drums are mounted in a horizontal position such as the one shown in figure 2 16 while others are mounted in a vertical position Another major difference in the design is the number of read write heads Some drums use only one read write head which s
151. mation The learning objectives for this chapter are listed below Upon completion of this chapter you will be able to do the following 1 Describe the history of computers 2 Describe how computers are classified 3 Explain how digital computers have changed during each generation 4 Describe the practical applications of digital computers in the Navy 5 Describe the initial steps needed to use a microcomputer 6 Explain storage media handling backups and the threats to storage media INTRODUCTION Digital computers are used in many facets of today s Navy It would be impossible for one VEETS module to cover all the ways they are used in any depth A few of these ways are covered later in this chapter The purpose of this module is to acquaint you the trainee with the basic principles techniques and procedures associated with digital computers We will use a desktop personal computer for most of the examples Personal computers should be more familiar to you than the large mainframes and the operating principles of personal computers relate directly to the operating principles of mainframe computers You will learn the basic terminology used in the digital computer world When you have completed these chapters satisfactorily you will have a better understanding of how computers are able to perform the demanding tasks assigned to them If we were to define the word computer we would say a computer is an instrument for perfor
152. mation from city to city across the nation and to other countries throughout the world through the expansion of local area networks into larger network configurations Combinations of telephone lines microwave radio links and satellites are used by these larger telecommunications networks to send information In 1965 the first successful communications satellite for business applications was launched It was not the only try it was preceded by many more primitive satellites With the launching of larger and more complex satellites the size and complexity of earth stations have been shrinking Since satellite services costs have been steadily decreasing it is becoming more cost effective to employ them for business type uses MODEMS Since both signals and data can be transmitted and received through cables communications lines we refer to them as input output channels And when we transmit data directly to a computer over long distances it becomes necessary to add two other devices one at each end of the communications line These devices are called modems fig 4 13 The word modem is an acronym for modulator demodulator combines first syllable of each word A modem converts the digital signal produced by your terminal or the computer to an audio signal suitable for transmission over the communications line The modem at the other end of the line converts the audio signal back to a digital signal before it is supplied to the computers or
153. medium can be processed by a computer Data items might include your service number your name your paygrade or any other fact Until some meaning has been given to the data nothing can really be determined about it therefore it remains data When this data has been processed together with other facts it then has meaning and it becomes information we can understand and properly use DATA REPRESENTATION Data is represented by symbols Symbols convey meaning only when understood The symbol itself is not the information but merely a representation of it Symbol meaning is one of convention fig 4 1 Symbols may convey one meaning to you and me another meaning to others and no meaning at all to those that do not know their significance Data must be reduced to a set of symbols that the computer can read and interpret before there can be any communication with the computer The first computers were designed to manipulate numbers to solve arithmetic problems But as you can see in figure 4 1 we create 4 1 use and manipulate many other symbols to represent facts in the world in which we live We are fortunate that early computer experts soon realized the need to manipulate nonnumerical symbols as well Manipulating these symbols is possible if an identifying code or coded number is assigned to the symbol to be stored and processed Thus the letters in a name such as ALBERT or CAROL can be represented by different codes as can all special ch
154. ming mathematical operations such as addition multiplication division subtraction integration vector resolution coordinate conversion and special function generation at very high speeds But the usage of computers goes well beyond the mathematical operations level Computers have made possible military scientific and commercial advances that before were considered impossible The mathematics involved in orbiting a satellite around the earth for example would require several teams of mathematicians for a lifetime Now with the aid of electronic digital computers the conquest of space has become reality 1 1 Computers are employed when repetitious calculations or the processing of large amounts of data are necessary The most frequent applications are found in the military scientific and commercial fields They are used in many varied projects ranging from mail sorting through engineering design to the identification and destruction of enemy targets The advantages of digital computers include speed accuracy reliability and man power savings Frequently computers are able to take over routine jobs releasing people for more important work work that cannot be handled by a computer HISTORY OF COMPUTERS The ever increasing need for faster and more efficient computers has created technological advances that can be considered amazing Ever since humans discovered that it was necessary to count objects we have been looking for easi
155. mprovements in software what kind of computer languages could be used on second generation computers 1 13 Q 32 What do the smaller circuits in third generation computers allow for Q 33 On third generation computers what results are gained by faster internal processing speeds Q 34 The data cell had a storage capacity of how many characters Q 35 What type of applications were most third generation computer systems designed to accomplish Q 36 What type of computers are small and inexpensive yet provide a lot of computing power Q 37 What does the acronym ROM stand for Q 38 What will be one of the future challenges involving computer power Q 39 What term is used for programs such as assemblers compilers and operating systems USES OF A DIGITAL COMPUTER In the modern computer world of today the uses of the digital computer are almost as limitless as a person s imagination New and better programs are being written everyday for easier and greater uses Consider how many mathematicians it would take to put an astronaut in orbit around the moon but it only takes one computer Think back to the days without word processing when a document had to be retyped entirely when any changes were needed Think back to the days of using an adding machine to prepare and revise budgets and accounting reports Let s look at three of the primary uses of general purpose digital computers in the Navy word processing accounting recordkeeping and w
156. mputer s internal storage is limited in size it cannot always hold all the data we need Second in secondary storage data and programs do not disappear when power is turned off Secondary storage is nonvolatile This means information is lost only if you the user intentionally erase it The three types of secondary storage we most commonly use are magnetic disk tape and drum MAGNETIC DISK The popularity of disk storage devices is largely because of their direct access capabilities Most every system micro mini and mainframe will have disk capability Magnetic disks resemble phonograph records round platters coated with a magnetizable recording material iron oxide but their similarities end there Magnetic disks come in many different sizes and storage capacities They range from 3 inches to 4 feet in diameter and can store from 2 5 million to 600 million characters bytes of data They can be portable in that they are removable or they can be permanently mounted in the storage devices called disk drive units or disk drives They can be made of rigid metal hard disks or flexible plastic floppy disks or diskettes as shown in figure 2 6 PERMANENT DISK STORAGE DISK PACKS FLOPPY DISKS DISKETTES Figure 2 6 Various types and sizes of magnetic disk storage Music is stored on a phonograph record in a continuous groove that spirals into the center of the record But there are no grooves on a magnetic disk Instead data is st
157. n much the same manner as the telephone exchange uses telephone numbers When a telephone number is dialed it causes the telephone exchange to energize certain switches and control lines to connect the dialing phone with the phone having the number dialed In a similar manner 2 2 each programmed instruction when executed causes the control section to energize certain control lines enabling the computer to perform the function or operation indicated by the instruction The program may be stored in the internal circuits of the computer computer memory or it may be read instruction by instruction from external media The internally stored program type of computer generally referred to only as a stored program computer is the most practical type to use when speed and fully automatic operation are desired Computer programs may be so complex that the number of instructions plus the parameters necessary for program execution will exceed the memory capacity of a stored program computer When this occurs the program may be sectionalized that is broken down into modules One or more modules are then stored in computer memory and the rest in an easily accessible auxiliary memory Then as each module is executed producing the desired results it is swapped out of internal memory and the next succeeding module read in In addition to the commands that tell the computer what to do the control unit also dictates how and when each specific operation
158. n s Handbook is a handy reference of commonly used general information such as electrical and electronic formulas color coding and naval supply system data Module 20 Master Glossary is the glossary of terms for the series Module 21 Test Methods and Practices describes basic test methods and practices Module 22 Introduction to Digital Computers is an introduction to digital computers Module 23 Magnetic Recording is an introduction to the use and maintenance of magnetic recorders and the concepts of recording on magnetic tape and disks Module 24 Introduction to Fiber Optics is an introduction to fiber optics Embedded questions are inserted throughout each module except for modules 19 and 20 which are reference books If you have any difficulty in answering any of the questions restudy the applicable section Although an attempt has been made to use simple language various technical words and phrases have necessarily been included Specific terms are defined in Module 20 Master Glossary Considerable emphasis has been placed on illustrations to provide a maximum amount of information In some instances a knowledge of basic algebra may be required Assignments are provided for each module with the exceptions of Module 19 The Technician s Handbook and Module 20 Master Glossary Course descriptions and ordering information are in NAVEDTRA 12061 Catalog of Nonresident Training Courses Throughout the text of this co
159. named Winchester The designers found that data density could be improved and storage capacity increased by reducing the flying height the distance of the read write heads over the disk surfaces when reading and writing By doing this smaller magnetized spots could be precisely written and then read The read write heads were moved so close to the disk that a human hair looked like a mountain in the path of the flying head Winchester technology reduces this potential problem by sealing the disks in a contamination free container This eliminates foreign objects from coming in contact with the read write heads Data can be physically organized in one of two ways on a disk pack depending on the manufacturer and the model of disk drive you are using One way uses the cylinder method and the other uses the sector method On diskettes data is organized using the sector method The cylinder method uses a cylinder as the basic reference point When you look at figure 2 10 view A you will see a disk pack containing six disk platters with 10 recording surfaces Imagine you are looking down through the disk pack from the top All the tracks with the same number line up vertically Together they are called a cylinder These 10 tracks one on each recording surface can be referenced by the 10 read write heads on the five access arms at each discrete location where the access arms can be positioned 2 11 000 199 ACCESS MECHANISM SACCESS 10 R
160. ngle user single tasking Single user multitasking Multiuser multitasking No EU Which of the following programs must be compatible with the operating system in use 1 CP M 86 2 UNIX 3 Applications 4 MS DOS THIS SPACE LEFT BLANK INTENTIONALLY 15 3 5 3 6 3 7 3 8 To overcome the applications software compatibility problem which of the following is done so the application can be run under several different operating systems 1 Some software comes in several versions 2 Computers are designed to accept all applications software 3 Software comes in a universal version 4 Operating systems are changed to be compatible What is another term for initial program load the system 1 Start 2 Boot 3 Kick 4 Run When the symbol A is on the screen of a computer crt it tells the operator user which of the following information 1 The system is not ready and drive A is busy 2 The system is ready and drive A is assigned as your secondary drive 3 The system is ready and drive A is assigned as your primary drive 4 The system is activating and no drive is available The three characters following each directory entry are called what 1 Files 2 Records 3 Locators 4 Extensions 3 11 Commands built into the operating system that control actions like diskcopy and rename are what type of commands 1 Independent 2 Copy 3 Spread 4 Utility To elimina
161. nsive and often resulted in errors Correcting errors or making modifications to these programs was a very tedious process SYMBOLIC LANGUAGES In the early 1950s mnemonic instruction codes and symbolic addresses were developed This improved the program preparation process by substituting letter symbols mnemonic codes for basic machine language instruction codes Each computer has mnemonic codes although the symbols vary among the different makes and models of computers The computer still uses machine language in actual processing but it translates the symbolic language into machine language equivalent Symbolic languages have many advantages over machine language coding Less time is required to write a program Detail is reduced Fewer errors are made Errors which are made are easier to find and programs are easier to modify PROCEDURE ORIENTED LANGUAGES The development of mnemonic techniques and macroinstructions led to the development of procedure oriented languages Macroinstructions allow the programmer to write a single instruction that is equivalent to a specified sequence of machine instructions These procedure oriented languages are oriented toward a specific class of processing problems A class of similar problems is isolated and a language is developed to process these types of applications Several languages have been designed to process problems of a scientific mathematical nature and others that emphasize file processing
162. ntains the UIC We provided specifications to the RPG program to tell it to accumulate totals from the detail individual data records until the UIC changed We then told it to print the total number of requisitions and total cost for that UIC We did not have it print each detail record although we could have The UIC is called the control field Each time the control field changes there is a control break Each time there is a control break the program prints the summary information After all records are read and processed it prints a summary line TOTALS for all UICs You can also use RPGs to generate a program to update data files Q 6 What programs eliminate the need for programmers to write new programs when all they want to do is copy print or sort a data file Q 7 How do we tell a utility program what we want it to do Q 8 What is the term given to arranging data records in a predefined sequence or order Q 9 To sort a data file what must you tell the sort program Q 10 What are report program generators used for PROGRAMMING LANGUAGES Programmers must use a language that can be understood by the computer Several methods can achieve human computer communication For example let us assume the computer only understands French and the programmer speaks English The question arises How are we to communicate with the computer One approach is for the programmer to code the instructions with the help of a translating dictionary
163. ntal symbols advanced symbols flowcharting template and flowcharting worksheet QUESTION 3 37 IS TO BE JUDGED TRUE 1 What information or data is needed OR FALSE 2 Where and how will the information be obtained 3 37 Fundamental symbols are standard for 3 Whatis the desired output 4 What is the computation time Once you have a thorough understanding of the problem what is the next step in programming l Gathering information 2 Coding the program 3 Flowcharting 4 Debugging 18 the military as directed by Department of the Navy Automated Data Systems Documentation Standards SECNAVINST 5233 1 1 True 2 False 3 38 Within a flowchart what type of symbols are used to specify arithmetic operations and relational conditions 1 Fundamental symbols 2 Graphic symbols 3 Arithmetic symbols 4 Arabic symbols 3 39 What is the graphic symbol for less than or equal to BR WN VIA V QUESTION 3 40 IS TO BE JUDGED TRUE OR FALSE 3 40 The flowchart worksheet is a means of standardizing documentation 1 True 2 False 3 41 To develop a flowchart which of the following must you know first What type of computer is to be used What problem you are to solve What code you are going to use What logic the computer will use to solve a problem T 9g 3 42 In solving a problem which of the following ways does a computer operate 1 Two steps at a time in random order It processes th
164. nts that describe the program and give a historical record of problems and or changes should be included 4 Operator instructions Items that should be included are computer switch settings loading and unloading procedures and starting running and termination procedures Implementation After the documentation is complete and the test output is correct the program is ready for use If a program is to replace a program in an existing system it is generally wise to have a period of parallel processing that is the job application is processed both by the old program and by the new program The purpose of this period 1s to verify processing accuracy and completeness Q 16 What is programming Q 17 In programming how many steps are involved in solving a problem on a computer Q 18 What is required before you can actually start to write or code a program Q 19 In flowcharting what method is used to represent different operations data flow equipment and so forth Q 20 What type of flowchart is constructed by the programmer to represent the sequence of operations the computer is to perform to solve a specific problem Q 21 How many tools are used in flowcharting Q 22 Is there a best way to construct a flowchart Q 23 What controls the computer during processing Q 24 What is the fundamental element in program preparation Q 25 What type of instructions permit addition subtraction multiplication and division Q 26
165. number of disks should be stacked horizontally 1 5 2 10 3 15 4 20 What is perhaps the most common source of a magnetic field that can affect a floppy disk 1 Crt s 2 Printer 3 Telephone 4 Disk drives In which of the following ways does smoke affect a computer It damages the electronics It causes the monitor to fail It coats the keyboard It causes buildup on disks and disk drives Ter What if anything can happen to a floppy disk when it is exposed to direct sunlight or excessive heat 1 Itcan become warped or distorted so it cannot be used 2 become sticky which stops the drive 3 Itcan lose part of the data recorded on it 4 Nothing it is not affected Typically floppy disks will operate only in what temperature range 1 40 to 120 degrees Fahrenheit 2 50to 120 degrees Fahrenheit 3 60 to 120 degrees Fahrenheit 4 70 to 120 degrees Fahrenheit 1 52 A floppy disk will accept what relative humidity range 1 54 l 2i 3 4 5 to 60 10 to 70 10 to 80 10 to 90 When a pencil or ballpoint pen is used to write on the label after it is attached to the disk what if anything can happen to a disk 1 Some of the data written on the label can be added to the disk 2 All of the data can be lost but the disk can be used again 3 The disk can be destroyed 4 Nothing there can be no effect In the computer world what method provides a means to ens
166. o tell it what you want the computer to do You may tell it to assemble or compile a COBOL program You may tell it to run the payroll or print inventory reports You may tell it to copy a tape using a utility program You may tell it to print the data from a disk file also using a utility program You may tell it to test a program This job information may be entered through the console or read into the computer from tape or disk It also may be entered by the programmer or user from a remote computer terminal The operating system receives and processes the job information and executes the programs according to that job information Software can be defined as all the stored programs and routines operating aids needed to fully use the capabilities of a computer Generally speaking we say If it is not hardware then it must be software OPERATING SYSTEMS The operating system is the heart of any computer system Through it everything else is done Basically operating systems are designed to provide the operator with the most efficient way of executing many user programs 3 An operating system is a collection of many programs used by the computer to manage its own resources and operations These programs control the execution of other programs They schedule assign resources monitor and control the work of the computer There are several types TYPES OF OPERATING SYSTEMS Operating systems are designed to provide various operating mo
167. obal 3 Satellite 4 Telephone The first successful communi cations satellite for business applications was launched in what year RUN N 4 47 4 48 4 49 4 50 When we transmit data directly to a computer over long distances it becomes necessary to add two other devices one at each end of the communications line These devices are called what 1 Modems 2 Printers 3 Converters 4 Input output buffers A modem converts the digital signal produced by your terminal or the computer to what type of signal suitable for transmission over the communications line 1 Video 2 Audio 3 Carrier 4 Hybrid If conversion of the digital signal to be transmitted were not carried out it would degenerate and become what 1 Lost 2 Strong 3 Doubled 4 Garbled Telephone lines are a frequently used type of communications channel They are often referred to by which of the following terms Land lines Microwave link High frequency link Communications lines BEN 4 51 4 53 4 54 26 In communications what name is given to those devices that serve to interconnect Connectors 2 System controllers 3 Interface elements 4 Impedance matchers When using a modem what are the two methods of data transmission Digital and analog Mechanical and light Continuous and non continuous 4 Asynchronous and synchronous WNre The transmission method that uses
168. of Defense U S Department of Transportation Xs pau 17 3 25 3 26 3 27 3 28 What are the two most familiar of the procedure oriented languages used for scientific or mathematical problems 1l PASCAL and FORTRAN 2 PASCAL and COBOL 3 COBOL and FORTRAN 4 BASIC and FORTRAN Compared with programs written in symbolic languages programs written in procedure oriented languages differ in which of the following ways 1 They can only be used with small computers 2 They can only be used with large computers 3 They can only be used with the computer for which the program was written 4 They can be used with a number of different computer makes and models Compared with symbolic languages procedure oriented languages have which of the following disadvantages 1 They require more space in memory and they process data at a slower rate 2 They require more space in memory and they process data too fast for some printers 3 They require a special memory and they process data at a slower rate 4 They require a special memory and they process data too fast for some printers Which of the following is a simple definition of programming 1 The process of planning which computer system to use 2 The process of planning the computer solution to a problem 3 The process of planning the mathematical solution to a problem 4 The process of planning which computer program to use 3 29 Which o
169. olvers amplifiers servo amplifiers summing networks potentiometers and linear potentiometers Figure 1 3 shows one of the Navy s electromechanical computers These computers are used in gun fire control and missile fire control Even though they are better than the mechanical computer they still have their drawbacks Of prime importance is that they are special purpose computers This means they can only be used for one job dependent on their design characteristics By today s Navy standards they are still too large and the maintenance time on them is excessive The need for a more accurate reliable versatile and smaller computer was recognized 1 4 COMPUTER MK47 COMPUTER 16 Figure 1 3 Electromechanical computer ELECTRONIC COMPUTERS Next came electronic computers The early electronic computers mathematical processes were solved by using electrical voltages only applied to elements such as amplifiers summing networks differentiating and integrating circuits The weak link in this type of electrical computation was the vacuum tube To correct this transistors which consume less power and last longer than vacuum tubes were used in the amplifiers Through technological research and development we have progressed from tubes to transistors to miniaturized circuits to integrated circuitry These advances have made it possible to reduce the size and weight of our computers Figure 1 4 is an example of one of our modern elec
170. omputer that is designed to perform a 1 15 specific operation is what kind of computer All purpose General purpose Special purpose Single purpose er How are the instructions that control a computer applied to a special purpose computer 1 From a stored program 2 Froma keyboard 3 From an input device 4 From built in instructions What is a drawback to the specialization of a special purpose computer 1 Low speed 2 Lack of versatility 3 Large size 4 High cost What gives a general purpose computer the ability to perform a wide variety of operations 1 It can store and execute different programs in its internal storage 2 Itis a much larger computer 3 It has a huge built in program 4 It can operate faster than other computers All analog computers are what type Mechanical Electromechanical Special purpose General purpose BROTOS What are computers called that combine the functions of both analog and digital Analog digital computers Mixed computers Duplexed computers Hybrid computers Xs 1 17 1 18 1 20 1 21 A digital computer knows how to do its work by what means 1 By a list of instructions called a program 2 By a list of instructions called a job sequence 3 By its hardware 4 By its peripheral equipment What is the most popular generic term for computer programs 1 Hardware 2 Software 3 Wordprocessing 4 Graphics
171. ood Once you have a thorough understanding of the problem the next step is flowcharting FLOWCHARTING Flowcharting is one method of pictorially representing a procedural step by step solution to a problem before you actually start to write the computer instructions required to produce the desired results Flowcharts use different shaped symbols connected by one way arrows to represent operations data flow equipment and so forth There are two types of flowcharts system data flowcharts and programming flowcharts A system data flowchart defines the major phases of the processing as well as the various data media used It shows the relationship of numerous Jobs that make up an entire system In the system data flowchart an entire program run or phase is always represented by a single processing symbol together with the input output symbols showing the path of data through a problem solution For example SYSTEM FLOWCHART PAY RECORDS PROCESS PAYROLL The second type of flowchart and the one we will talk about in this section is the programming flowchart It is constructed by the programmer to represent the sequence of operations the computer is to perform to solve a specific problem It graphically describes what is to take place in the program It displays specific operations and decisions and their sequence within the program For example PROGRAMMING FLOWCHART INPUT EMPLOYEE HOURS PAYRATE HOURS vee
172. orage device in which information is stored on one or both sides of a rigid disk that can be magnetized The disk is rotated by a disk drive and information is stored and retrieved by one or more magnetically sensitive read write heads AI 3 DISKETTE A mass storage device in which information is stored on one or both sides of a flexible disk that can be magnetized The diskette is rotated by a diskette drive and information is stored and retrieved by one or more magnetically sensitive read write heads Diskettes are also called floppy disks because the disk bends easily DOWNTIME The length of time the computer is not operating either because of preventive maintenance scheduled downtime or a malfunction nonscheduled downtime EBCDIC Extended Binary Coded Decimal Interchange Code An 8 bit coding system for representing uppercase and lowercase letters numbers and special characters EPROM The acronym for erasable programmable read only memory FIELD DATA An item of information in a data record One or more related characters that are treated as a unit of information FILE A collection of related records for example a payroll file Any collection of records holding similar data or transactions that are stored together to permit systematic access and modification FILE MASTER The file that contains all the data records in up to date form It is a main reference file of relatively more permanent information which is u
173. ored on all disks in a number of invisible concentric circles called tracks Each track has a designated number beginning with track 000 at the outer edge of the disk The numbering continues sequentially toward the center to track 199 800 or whatever the highest track number is No track ever touches another fig 2 7 The number of tracks can vary from 35 to 77 on a floppy disk surface and from 200 to over 800 on hard disk surfaces 2 9 READ WRITE HEAD TRACK 000 Figure 2 7 Location of tracks on the disk s recording surface Data is written as tiny magnetic bits or spots on the disk surface Eight bit codes are generally used to represent data Each code represents a different number letter or special character In chapter 4 you ll learn how the codes are formed When data is read from the disk the data on the disk remains unchanged When data is written on the disk it replaces any data previously stored on the same area of the disk Characters are stored on a single track as strings of magnetized bits 0 s and 1 s as shown in figure 2 8 The 1 bits indicate magnetized spots or ON bits The 0 bits represent unmagnetized portions of the track or OFF bits Although the tracks get smaller as they get closer to the center of the disk platter each track can hold the same amount of data because the data density is greater on tracks near the center TRACK 025 Figure 2 8 A string of bits written to disk on a sing
174. ork center uses WORD PROCESSING One of the more widespread uses of the computer is word processing The word processor can be considered a typewriter with a display screen To the hundreds of thousands of word processor users the computer is nothing more than a typewriter Both have keyboards and both have a mechanism for making the image of the character you strike on the keyboard appear on some type of visual medium When using an electric typewriter the process is strictly mechanical When you press the key it causes the type face to strike the paper and in so doing it leaves an impression In the computer the process is more indirect A program stored in the computer s memory causes a visual representation to appear on a crt cathode ray tube or at a printer However from the view point of the user the result is the same a printed document The great advantage of computers over typewriters is in correcting errors In the past correcting a document with a typewriter has meant typing it all over again Since computers allow the movement of information from one part of memory to another it is possible to make many changes on a document and print the result If the document is still not correct only the changes need to be entered The use of computers in this particular way came to be known as word processing A further breakthrough came with the development of word processing application programs for microcomputers These programs cost
175. orrect an existing document print a document and so on You ll learn more about both the operating system and application programs in chapter 3 Each application program will have its own set of instructions to follow In addition to printed documentation many will include online HELP screens you can display while you are working These will tell you how to perform a given function or operation Another area that needs your constant attention relates to handling floppy disks and making backup copies to be sure your work is not lost STORAGE MEDIA HANDLING AND BACKUP Floppy disks fig 1 13 are one means by which you will store data files that you create either directly or in backing up the data you store on hard or fixed disk For this reason and because floppy disks are extremely fragile you should follow certain guidelines to ensure their proper care and handling This includes properly labeling and backing up disks DISK LINER Jac WRITE PROTECT NOTCH a DISK JACKET TIMING HOLE READ WRITE SLOT DISK ENVELOPE Figure 1 13 Floppy disk Handling Never touch the exposed surface of a disk As you know or will learn most of the surface of the actual disk is protected most of the time however there are areas that are exposed These areas are the timing hole and the read write slots Touching an exposed area can ruin that particular area If you are familiar with Murphy s Law you will realize the area
176. ot matrix print head builds characters out of the dots created by the pins in the matrix Figure 2 25 view A shows what dot matrix characters look like when printed 2 25 rxXcC rommoouo o c lt S lt cAMADVOZEZ gt ON lt A DOT MATRIX CHARACTERS B DOT MATRIX PRINT MECHANISM VIEWED FROM THE FRONT 0000000 LP C ALLOWABLE SPACE FOR EACH PRINTABLE CHARACTER D THE LETTER H USING A 5 BY 7 DOT MATRIX Figure 2 25 Dot matrix printing The dot matrix is defined in terms of rows and columns of dots A 5 by 7 matrix uses up to five vertical columns of seven dots to create a character An example of a 5 by 7 matrix printing the letter H is shown in figure 2 25 view D The size of dot matrixes varies from a 5 by 7 matrix to as large as a 58 by 18 matrix A number of dot matrix printers use a single vertical column of pins to print characters as shown in figure 2 25 view B The characters are printed by moving stepping the print head a small amount and printing the vertical columns one at a time until the character is printed as shown in figure 2 25 views C and D The size of the matrix determines the quality of the printed character In other words the more dots used to print a character the better the character is filled in and the higher its print quality Dot matrix printers are faster than the daisy wheel printers with speeds ranging from 60 to 350 cps but their prin
177. our own you will find we don t usually think in small detailed sequential steps However that is exactly how a computer operates one step after another in a specified order Therefore it is necessary for you to think the problem solution through step by step You might clarify the problem as shown by the Problem Definition in figure 3 6 3 16 PROBLEM DEFINITION MORTGAGE AMORTIZATION This program is to de termine the monthly amount of interest A and amount applied to the principal P of the mortgage giving the balance B at the end of a thirty six month period INPUT The monthly payment is to be en tered as variable D the beginning balance of the mortgage is to be entered as variable B and the annual in terest rate is to be entered as variable I This input is to be entered into the sys tem via the terminal OUTPUT The end result is to be a listing dis playing the amount ap plied to principal and interest and the cur rent loan balance each month with one final entry showing the final payment on the mortgage START INPUT MONTHLY PMT LOAN AMT INT RATE CALCULATE MONTHLY INTEREST RATE COMPUTE COMPUTE AMOUNT APPLIED TO INTEREST COMPUTE AMOUNT APPLIED TO PRINCIPAL COMPUTE LOAN BALANCE PRINT MONTHLY PRINT LOAN BALANCE Figure 3 6 Problem definition and programming flowchart 3 17 After you have this level of narrative problem definition
178. ows a keyboard combined with a crt on a microcomputer CRT DISPLAY SCREEN Figure 2 26 Keyboard combined with a crt and microcomputer The primary purpose of a keyboard is to enter or input alphanumeric numbers letters and special characters character codes The major grouping of keyswitches on a keyboard will be in one of the two styles of a typewriter keyboard arrangement QWERTY or DVORAK The typewriter keyswitches are arranged in 4 rows of 10 or more switches The keyboard arrangement shown in figure 2 27 is QWERTY The rows are usually offset to the row above to make it easier to reach all the keys when typing The tops of the individual keyswitches are sculptured to conform to the shape of the human finger 2 27 DATA SET POWER ON READY PP EEE ET CLO NUMBER CURSOR TYPEWRITER KEYS ____ ENTRY CONTROL KEYPAD KEYS m S BACK 4 LLEDBEDBDLELLDLLLELIZ FUNCTION KEYS b OGL DEL CELFLEELLLELELLLLIILDLI CAPS CLELELELEELLLELLLLI PEELE CLE EL COD coo Figure 2 27 Keyboard layout Other groupings of keyswitches are used for special purposes such as number entry calculator keypads special function switches F1 F12 and cursor control keys The special function switches allow an operator to use the special functions designed in the software For example in a word processing program you can use them to spell check a document search for a particular portion of text move text from
179. pe of language Ly form Q 12 When were mnemonic instruction codes and symbolic addresses developed Q 13 What led to the development of procedure oriented languages Q 14 What computer language was developed for mathematical work Q 15 What are two disadvantages of procedure oriented languages PROGRAMMING Programming is simply the process of planning the computer solution to a problem Thus by writing 1 Take the reciprocal of the resistance of all resistors expressed in ohms 2 Sum the values obtained in step 1 3 Take the reciprocal of the sum derived in step 2 A generalized process or program for finding the total resistance of a parallel resistance circuit has now been derived To progress from this example to preparing a program for a computer is not difficult However one basic characteristic of the computer must be kept in mind It cannot think It can only follow certain commands and these commands must be correctly expressed and must cover all possibilities Thus if a program is to be useful in a computer it must be broken down into specifically defined operations or steps Then the instructions along with other data necessary for performing these operations or steps must be communicated to the computer in the form of a language or code that is acceptable to the machine In broad terms the computer follows certain steps in executing a program It must first read the instructions sequentially unless otherwis
180. r a software house or a central design agency ANSWERS TO QUESTIONS Q1 THROUGH Q33 A 1 The operating system A 2 Single user single tasking A 3 Multiuser multitasking A 4 Because to use applications software it must be compatible with the operating system A 5 Some software comes in several versions so it can run under several different operating systems A 6 Utility programs A 7 By providing information about files data fields and the process to be used A 8 Sorting A 9 What data field or fields to sort on A 10 To generate programs to print detail and summary reports of data files A 11 Machine A 12 In the early 1950 s A 13 The development of mnemonic techniques and macroinstructions 4 14 FORTRAN 3 28 4 15 4 16 4 17 4 18 4 19 4 20 4 21 4 22 A 23 A 24 4 25 4 26 4 27 A 28 4 29 4 30 4 31 4 32 4 33 They require more space in memory and they process data at a slower rate than symbolic languages The process of planning the solution to a problem Four Advance preparation Different shaped symbols A programming flowchart Four No there isn t a way to standardize problem solution Coded instructions The instruction Arithmetic In the computer manufacturers or software designers user s manual Bugs To determine that all data can be processed correctly and that the output is correct Off the shelf programs designed for specific classes of applications
181. r checking method in which the binary digits in a character or word are added and the sum is checked against a single previously computed parity digit The check tests whether the number of one bits in a character or word are odd or even depending on the parity of the computer PASSWORD A protected word or string of characters that identifies or authenticates a user for access to a specific resource such as a file or record PERIPHERAL EQUIPMENT Equipment used for data entry storage or retrieval but which is not a part of the central processing unit Peripherals include crt displays terminals printers and mass storage tape disk and drum devices PERSONAL COMPUTER PC A computer usually a microcomputer that is more affordable than minicomputers or mainframes and is used by one person at a time PICTURE ELEMENT Synonym for pixel See pixel PIXEL computer graphics the smallest element of a display surface that can be independently assigned color or intensity AI 7 PRIMARY STORAGE See storage primary PRINTER A device used with a computer to produce hard copy printed output PROGRAM 1 Verb The act of writing instructions for computer execution 2 Noun The set of instructions that tells the computer the steps to execute to automatically solve a problem PROGRAM FLOWCHART See flowchart PROM Acronym for programmable read only memory PUNCHED CARD A card punched with hole patterns th
182. rding proc essed information is an Output function DECISION SYMBOL is used to depict a point in a program at which a branch to one of two or more alternate paths is possible TERMINAL INTERRUPT SYMBOL represents a terminal point in a flowchart for example start stop halt delay or inter rupt CONNECTOR SYMBOL repre sents a junction in a line of flow to another part of the flowchart A common identifier such as an alphabetic character number or mnemonic label is placed within the exit and its associated entry FLOWLINE SYMBOL is used to represent flow direction by lines drawn between symbols Normal direction of flow is left to right and top to bottom If the direc tion of flow is other than normal arrowheads are required at the point of entry EXAMPLE COMPUTE MONTHLY INTEREST Rz 1 12 INPUT B D YES START STOP COMPUTE MONTH OF LOAN LAST MONTH OF LOAN PRINT LOAN BALANCE DUE EXPLANATION Divide I by 12 assign value to R Enter these values through the terminal store in locations B D I If A is NOT equal to B take NO branch If A is equal to B take YES branch START STOP flow chart at this point This represents the EXIT point and the ENTRY point in a flowchart Initial processing is shown here If the NO branch is taken the processing block is performed again If the YES branch is taken the INPUT OUTPUT operation is performed Figure 3 3
183. re 4 8C Core storage with DP 3 represented using 8 bit EBCDIC code STORAGE CAPACITY AND ADDRESSES The storage capacity of an address is designed and built into the computer by the manufacturer Over the years several different design approaches to partition primary storage have been used With this in mind let s take a look at some of the ways primary storage is partitioned into addresses One way to design or organize the primary storage section is to store a fixed number of characters bytes at each address location We can then reference these characters as a single entity called a word as illustrated in figure 4 9 view A The name CHARLIE address location 400 or the amount he is paid in this case 69 00 address location 401 are each treated as a single word Computers that are built to 4 10 retrieve manipulate and store a fixed number of characters in each address are said to be word oriented word addressable machines or fixed word length computers ADDRESS LOCATIONS BYTES AAs ASSAI CHECK BITC 1 0 0 0 1 1 i 1 3 1 2 1 i 1 1 1 1 9 0 9 0 1 1 Q 21 1 ZONE 1 1 13 1 10 10 10 i d 1 d gd oi d 1 8 BITS X 0 0 50 0 0 0 3 i 1 z 6 0 6 4 1 9 0 0 1 t 1 1 8 1 3 O 1 9 0 0 1 1 1 NUMERIC J4 o o 1 0 0 0 1 6 BITS 2 1 9 1 90 8 0 0 1 1 1 6 1 P1 6 3 3d d 10 1 6 0 0 1 0 1 1 6 8 A FIXED LENGTH WORDS CONTAINING EIGHT CHAR
184. rks 4 17 storage access methods 4 15 to 4 16 direct access storage 4 15 random access storage 4 16 sequential access storage 4 15 Data storage concepts 4 8 to 4 15 Debugging 3 21 Desk checking 3 21 Direct access storage 2 9 2 16 4 15 Disk cylinder method 2 11 Disk pack 2 22 Disk sector method 2 12 Disks magnetic 2 8 to 2 12 Displays formatted 2 31 Displays unformatted 2 31 Document compilation programs 3 24 Documentation 3 21 to 3 22 Dot matrix printers 2 25 Drum magnetic 2 16 to 2 18 E EBCDIC 4 3 to 4 6 Erasable programmable read only memory EPROM 2 8 Extended binary coded decimal interchange code EBCDIC 4 3 to 4 6 Extensions 3 3 F Field 4 14 File 4 14 Firmware 2 7 Fixed word length computers 4 12 Flexible computers 4 12 Floppy disk drive units input output 2 23 Flowcharting 3 11 to 3 18 FORTRAN 3 7 Function switches 2 28 G Generations digital computers 1 10 to 1 14 Glossary AI 1 to AI 9 Graphics software 3 26 to 3 27 H Handshaking 4 18 Hardware 2 1 to 2 35 central processing unit cpu 2 1 to 2 4 arithmetic logic section 2 3 control section 2 2 to 2 3 memory internal storage section 2 4 classifications of internal storage 2 7 to 2 8 erasable programmable read only memory EPROM 2 8 programmable read only memory PROM 2 8 random access memory RAM 2 8 read only memory ROM 2 7 input output devices external 2 18 to 2 33 display
185. rm of bits concurrently across the width of the tape characteres BCDEFGHI JKLMNOPGR STUVYVWXYZ 01234567183 CHECK EIT c 1 E 2 ZONES 3 4 TRACKS NUMERIC 4 5 i BITS z 6 1 7 SEVEN TRACK MAGNETIC VIEW CHARACTEREITS ABCOEFGHI JKLMNOPGR STUVWwXYZ 0123456789 TRACKS NUMERIC BIT 1 TRACK 4 NUMERIC BIT 2 2 TRACK 6 ZOHEEIT 3 TRACK 0 ZOHEEIT 4 4 TRACK 1 5 TRACK 21 ZONEBIT 2 PARITY BIT 5 PARITYBIT ZINE BIT 1 T TRACK 2 NUMERIC BIT 1 TRACK 7 NUMERIC EIT 4 3 TRACK 5 NINE TRACK MAGNETIC TAPE VIEW B Figure 2 13 Multi track magnetic tape The amount of data or the number of binary digits 0 and 1 bits that can be written stored on a linear inch of tape is known as the tape s recording density Common recording densities for multitrack tapes range from 200 to 6 250 bits bytes per inch BPI Also note that sometimes the density of a tape 1s 2 14 referred to as the number of frames per inch FPI or characters per inch CPI rather than BPI Regardless of which term is used a frame or byte is a group of related bits that make up a single character written across the width of the tape Most magnetic tape units are capable of reading and writing in several different densities Magnetic tapes have many common features and data recording formats Each tape is physically marked in some manner to indicate where reading and writing on tape is to begin known as the beginning
186. ronics and proceeds into the characteristics of matter energy and direct current dc It also describes some of the general safety precautions and first aid procedures that should be common knowledge for a person working in the field of electricity Related safety hints are located throughout the rest of the series as well Module 2 Introduction to Alternating Current and Transformers is an introduction to alternating current ac and transformers including basic ac theory and fundamentals of electromagnetism inductance capacitance impedance and transformers Module 3 Introduction to Circuit Protection Control and Measurement encompasses circuit breakers fuses and current limiters used in circuit protection as well as the theory and use of meters as electrical measuring devices Module 4 Introduction to Electrical Conductors Wiring Techniques and Schematic Reading presents conductor usage insulation used as wire covering splicing termination of wiring soldering and reading electrical wiring diagrams Module 5 Introduction to Generators and Motors is an introduction to generators and motors and covers the uses of ac and dc generators and motors in the conversion of electrical and mechanical energies Module 6 Introduction to Electronic Emission Tubes and Power Supplies ties the first five modules together in an introduction to vacuum tubes and vacuum tube power supplies Module 7 Introduction to Solid State Devic
187. rt They are not good at guessing what you meant You ll quickly learn there are a few things that can go wrong at this point in which case the computer will give you an error message on the display screen similar to this Device Error This means the computer is not reading anything in A drive Check for 1 No floppy disk in drive A 2 Floppy disk inserted incorrectly in drive 3 Lock handle on drive A not lowered Another error message you might receive at this time is No System This means the computer is reading a properly inserted floppy disk but the disk does not have an operating system on it Replace the disk with one that does contain the operating system Once the operating system is properly booted loaded you will see a display similar to this A gt You now have what is called a prompt At this point you can tell the computer what to do next such as run an application program for example word processing accounting or recordkeeping Running an Application Program To load an application program into the computer from drive A you put the disk with the application program in disk drive A Next you type the name of the program following the operating system prompt A gt A gt WORDPROC This tells the system what program to load and run in this case Word Processing The computer then does what the application program tells it If the application is word processing the system is ready for you to type a new document c
188. ry ROM Only the manufacturer No Read write memory By giving the computer the address of the location where the data is stored or is to be stored Already programmed by the manufacturer or in a blank state If a mistake is made and entered it cannot be corrected or erased Erasable programmable read only memory With a burst of ultra violet light Largely because of their direct access capabilities In a number of invisible concentric circles called tracks A disk address 2 34 4 29 4 30 4 31 4 32 4 33 4 34 4 35 4 36 4 37 4 38 4 39 4 40 4 41 4 42 4 43 4 44 4 45 4 46 4 47 4 48 4 49 By the bits per inch of track and the tracks per inch of surface By cylinder or sector Recording density The usable recording reading writing surface or usable storage area The tracks in which the data is stored are assigned to channels that form circular bands around the drum Sectors To write data on or read data from a magnetic tape The speed at which the tape is moved past the read write head and the density of the recorded information It gives us fast immediate access to specific data without having to examine each and every record from the beginning A thin flexible platter coated with magnetic material so characters can be recorded 8 inch 5 1 4 inch and 3 1 2 inch Printers Daisy wheel dot matrix ink jet and laser To enter or input alphanumeric character codes The d
189. ry ROM on a piece of equipment no bigger than a desktop calculator more about ROM 1n chapter 2 The future challenge will not be in increasing the storage or increasing the computer s power but rather in properly and effectively using the computing power available This is where software programs such as assemblers report generators subroutine libraries compilers operating systems and applications programs will come into play see chapter 3 Some believe developments in software and in learning how to use these extraordinary powerful machines we already possess will be far more important than further developments in hardware over the next 10 to 20 years As a result the next 20 years during your career may be even more interesting and surprising than the last 20 years Q 23 Technological advancement is measured by what in the electronic computer world Q 24 What does each generation of computer systems indicate Q 25 What were computers of the first generation characterized by Q 26 How did vacuum tubes cause a problem for first generation computers Q 27 In first generation computers internal processing functions were measured by what division of time Q 26 The software computer program used on first generation computers was what type Q 29 How were processing speed and reliability increased in second generation computers Q 30 In second generation computers how was the storage capacity greatly increased Q 31 With i
190. s A through I 1101 1s used for the characters J through R and 1110 is the zone combination used for characters S through Z The bit pattern 1111 is the zone combination used when representing decimal digits For example the code 11000001 is equivalent to the letter A the code 11110001 is equivalent to the decimal digit 1 Other zone combinations are used when forming special characters Not all of the 256 combinations of 8 bit code have been assigned characters Figure 4 5 illustrates how the characters DP 3 are represented using EBCDIC 4 4 ALPHABET IC CHARACTERS UPPERCASE LOWERCASE E BCcDiC IH HE BINARY DECI 2122 421 5421 1100 60001 1100 0010 1100 0011 1100 0100 1100 0101 1100 0110 1100 0111 1100 1000 1100 1001 em E C m gt WA 08 Oh LA RI er PFO n 0 UC 3 me 1101 0001 1101 0010 1101 0011 1101 0100 1101 0101 1101 0110 1101 0111 1101 1000 1001 UD nj CR LA de Lu Fa m SOD O39 De ru Wu UD sd CR QA ein be J L M H 0 0010 00211 0100 0101 0110 0111 1000 1001 gt ee ee a a eee APARNA AAAAaAAAARA W UB ER LEE Lu hE OR X XE X UR xd LA Lu Kd HNC Ce ew NUMERIC CHARACTERS Figure 4 4 Eight bit EBCDIC coding chart including hexadecimal equivalents D P 3 1100 0100 1101 0111 0110 0000 1111 0011 Figure 4 5 DP 3 represented
191. s and Data Processing Anaheim Publishing Co Brea Calif 1980 U S Army Signal School Digital Computers FM 11 72 Fort Gordon Ga 1977 Van Overberghe Albert G Jr DPCS Data Processing Technician 3 NAVEDTRA 10263 NETPDTC Pensacola Fla 1987 Vermillion Associates Computer Concepts For Small Business Heath Company Benton Harbor Mich 1978 AII 1 MODULE 22 INDEX A Access arms 2 22 Accounting and recordkeeping 1 15 Ada 3 7 Alphanumeric 2 27 American Standard Code for Information Interchange ASCII 4 6 to 4 7 Arithmetic instructions 2 3 ASCII 4 6 to 4 7 Asynchronous transmission 4 18 Auxiliary storage see storage secondary B Baseband communications channel 4 16 BASIC 3 7 Bits and bytes 4 8 4 13 Blocking factor 2 15 Booting the system 1 18 Bootstrap program 2 4 Broadband communications channel 4 17 Bubble storage 2 6 Bytes 4 8 4 13 Central processing unit cpu 2 1 to 2 4 arithmetic logic section 2 3 control section 2 2 to 2 3 memory internal storage section 2 4 Character oriented addressable computers 4 11 Check bit 4 7 COBOL 3 7 Coding program 3 19 to 3 21 Coding systems 4 3 to 4 8 Collating sequence 3 4 Communications data 4 16 to 4 18 Communications software and hardware 3 24 Compiler programs 3 24 Computer coding systems 4 3 to 4 7 ASCII 4 6 to 4 7 EBCDIC 4 3 to 4 6 Computer generations digital 1 10 to 1 14 first gener
192. se number Explanations for completing the answer sheets are on the answer sheet Do not use answer sheet reproductions Use only the original answer sheets that we provide reproductions will not work with our scanning equipment and cannot be processed Follow the instructions for marking your answers on the answer sheet Be sure that blocks 1 2 and 3 are filled in correctly This information is necessary for your course to be properly processed and for you to receive credit for your work COMPLETION TIME Courses must be completed within 12 months from the date of enrollment This includes time required to resubmit failed assignments PASS FAIL ASSIGNMENT PROCEDURES If your overall course score is 3 2 or higher you will pass the course and will not be required to resubmit assignments Once your assignments have been graded you will receive course completion confirmation If you receive less than a 3 2 on any assignment and your overall course score is below 3 2 you will be given the opportunity to resubmit failed assignments You may resubmit failed assignments only once Internet students will receive notification when they have failed an assignment they may then resubmit failed assignments on the web site Internet students may view and print results for failed assignments from the web site Students who submit by mail will receive a failing result letter and a new answer sheet for resubmission of each failed assignmen
193. solve a horizontal line of display This characteristic remains true up to a point called the merge point where the variation between the lines cannot be detected by the human eye DISPLAYING DATA ON RASTER SCAN SCREENS Raster scan displays are repetitive in nature The raster frame is displayed approximately 30 times a second The basic video monitor does nothing more than display the video signals it receives If no video signals are received then all the picture elements remain blanked and the screen is blank in each frame For data to be displayed accurately each and every frame must blank and unblank the same picture elements 2 30 The digital logic that drives video monitors is designed to take advantage of the repetitive nature of frames There can only be a fixed number of picture elements on the screen of a display therefore the contents of the display screen are organized into a data unit called a page The page contains the status of every picture element on the display screen The page is usually stored in some form of random access memory RAM chips being the most common The contents of page memory or as it is sometimes called video memory are continually scanned by the video generation logic and used to develop the video signals for the picture element display The picture element locations in page memory are read in time to develop the video signals for the picture element display on the horizontal lines If the di
194. splay is to be changed the contents of page memory must be changed The display on the screen changes as new data is stored in page memory Two addressing methods are used with page memory Unformatted Displays Displays that reference page memory by picture element address are called unformatted or fully populated displays These displays are more commonly used for graphics rather than alphanumeric characters Formatted Displays Often displays are organized by character position and line number These displays are known as formatted displays This display method is used with devices displaying alphanumeric characters only or those with an alternate graphic capability The video generation logic of these types of displays scans the entire page memory as before to generate the display picture elements The difference is in the way the new data is written into the page memory Individual picture element addresses are not used Character addresses are used to reference page memory The screen is organized into character lines Each line is made up of a fixed number of character positions or columns A fixed number of character lines can be displayed A common arrangement found on display screens is twenty five 80 character lines or 2 000 characters The character set that can be displayed on a device s formatted screen is stored in ROMs or PROMS That is the dot matrix picture element patterns for each individual character to be displayed
195. ss memory than the sort process since the intermediate sort work files are all in the same sequence Records from each work file can be read the sort keys compared based on the collating sequence and sort parameters and records written to the output file maintaining the specified sequence REPORT PROGRAM GENERATORS Report program generators RPG are used to generate programs to print detail and summary reports of data files Figure 3 1 is an example of a printed report RPGs were designed to save programming time Rather than writing procedural steps in a language like BASIC or COBOL the RPG programmer writes the printed report requirements on specially designed forms SUMMARY OF REQUISTIONS BY UNIT IDENTIFICATION CODE 40 000 00 Figure 3 1 Printed report using a report program generator RPG program 3 5 Included in the requirements are an input file description the report heading information lines the input data record fields the calculations to be done and the data fields to be printed and summarized The RPG program takes this information and generates a program for the specific problem You then run that program with the specified input data file to produce the printed report The input data file must be in the sequence in which you want the report to summarize the data In our example fig 3 1 we summarized requisitions based on unit identification codes UIC We first sorted the input data file on the field that co
196. stalled in ROM by the manufacturer are called what 1 Firmware 2 Software 3 Hardware 4 Diskware What kind of memory used inside computers has a read write capability without any additional special equipment 1 ROM 2 RAM 3 EPROM 4 PROM A special device is needed to burn the program into what type of memory 1 ROM 2 PROM 3 ERAM 4 RAM EPROM can be erased by what method With a current charge With a voltage change With a burst of ultra violet light With a special program TU To coat magnetic disks what magnetizable recording material is used 1 Plastic 2 Mylar amp 3 Aluminum oxide 4 Iron oxide What is the size range of the diameters of magnetic disks 3 inches to 4 feet 4 inches to 3 feet 5 inches to 6 feet 6 inches to 5 feet JS US DAE 2 28 2 29 2 30 2 31 2 32 Data is stored on all disks in a number of invisible concentric circles called what 1 Cracks 2 Grooves 3 Paths 4 Tracks A floppy disk surface has what maximum number of tracks 1 66 2 77 3 88 4 99 When data is written on a disk in the same area where data is already stored the old data is affected in which of the following ways if at all It is moved to a new area It is mixed with the new data It is replaced It is not affected Tope How are records on a track separated 1 By a gap in which no data is recorded 2 Byagapin which the name of the record
197. stroyed or becomes unusable the backup file can be used to recreate the file or data base Two media are commonly used for backup disk or tape Disk The most common method of creating a backup for a microcomputer is to use a floppy disk and the diskcopy procedure This is accomplished by using the original data base or file and copying the information onto a blank floppy disk The instructions for this procedure will be provided with the particular computer and program you are using Tape Another method of creating a backup is to use magnetic tape The information contained on your disk whether it is a data base or file can be copied onto a tape The instructions for this procedure will also be provided with the particular computer and program you are using Q 51 What is a central set of programs called that manages the execution of other programs and performs common functions like read write and print Q 52 What is the function of a built in program called a bootstrap loader Q 53 When you see the error message NO SYSTEM what does it mean Q 54 When an operating system prompt A gt is displayed on the screen what do you enter from the keyboard to load an application program Q 55 If disks are stored horizontally how many can be stacked Q 56 What can exposure to a magnetic field do to the data on a disk 1 21 Q 57 What is the temperature range within which a disk will operate Q 56 What is the most common method to
198. sually updated periodically FIRMWARE A set of program instructions a microprogram permanently stored in read only memory FLAT PANEL DISPLAY A display device that consists of a grid of electrodes in a flat gas filled panel The image can persist for a long period of time without refresh FLOPPY DISK See diskette FLOWCHART A graphic representation of the processing steps logic of a program a program flowchart or the inputs outputs and processing steps of a system a systems data flowchart The graphic representation uses symbols to represent operations and directional lines to indicate sequence and direction of flow FORMA T The arrangement or layout of data in or on a data medium FORTRAN FORmula TRANslator A high level programming language for scientific and mathematical applications FULL DUPLEX CHANNEL A channel that provides for simultaneous transmission in both directions such as the telephone GENERAL PURPOSE COMPUTER A computer designed to operate on a program of instructions for the purpose of solving many different types of processing problems GENERATIONS OF COMPUTERS Historically the distinctive types of computers from the 1940s to the present the first generation was based on vacuum tubes the second on transistors the third and current features integrated circuits Recent developments involve the use of VLSI very large scale integration and semiconductor memories GRAPHICS The
199. t COMPLETION CONFIRMATION After successfully completing this course you will receive a letter of completion ERRATA Errata are used to correct minor errors or delete obsolete information in a course Errata may also be used to provide instructions to the student If a course has an errata it will be included as the first page s after the front cover Errata for all courses can be accessed and viewed downloaded at http www advancement cnet navy mil STUDENT FEEDBACK QUESTIONS We value your suggestions questions and criticisms on our courses If you would like to communicate with us regarding this course we encourage you if possible to use e mail If you write or fax please use a copy of the Student Comment form that follows this page For subject matter questions E mail n315 products cnet navy mil Phone Comm 850 452 1001 ext 1728 DSN 922 1001 ext 1728 FAX 850 452 1370 Do not fax answer sheets Address COMMANDING OFFICER NETPDTC N315 6490 SAUFLEY FIELD ROAD PENSACOLA FL 32509 5237 For enrollment shipping grading or completion letter questions E mail fleetservices cnet navy mil Phone Toll Free 877 264 8583 Comm 850 452 1511 1181 1859 DSN 922 1511 1181 1859 FAX 850 452 1370 Do not fax answer sheets Address COMMANDING OFFICER NETPDTC N331 6490 SAUFLEY FIELD ROAD PENSACOLA FL 32559 5000 NAVAL RESERVE RETIREMENT CREDIT If you are a member of the Naval Reserve
200. t quality is not as good 2 26 Ink Jet Printers Ink jet printers employ a technique very similar to the way we use a can of spray paint and a stencil A spray of electrically charged ink 1s shot under pressure toward the paper Before reaching the paper the ink is passed through an electrical field which forms the letters in a matrix form The print resulting from this process consists of easy to read high quality characters Some manufacturers use large droplets of ink for faster printing while others use small droplets for better clarity but with slightly reduced printing speeds These printers can print up to 300 cps characters per second Laser Printers Laser printers direct a beam of light through a rotating disk containing the full range of print characters The appropriate character image is directed onto photographic paper which is then put through a toner developed and used to make additional copies The print resulting from this process consists of sharp clean images that are easy on the eyes These printers can print up to 20 000 plus lines per minute or 26 666 cps characters per second KEYBOARDS INPUT A keyboard is nothing more than an array of switches called keyswitches Keyboards are designed to input a code to the computer when a keyswitch is depressed Each keyswitch or key on the keyboard is assigned a particular code value and it is usually imprinted with a legend to identify its function Figure 2 26 sh
201. t matrix print head prints a character It takes several horizontal lines and picture elements on each line to create a character Figure 2 29 shows the generation of the character A 7 picture elements wide and 9 horizontal lines high The character is built using what is in effect a 7 by 9 dot matrix The picture elements used to build the character would be at full intensity the remaining picture elements in the matrix would be blanked If dark characters on a lighted screen were desired then the character picture elements would be blanked and the remainder displayed at full intensity Figure 2 29 A 7 by 9 picture element character Approximately 640 picture elements per horizontal line are required for the display of an 80 character line Therefore you can expect 140 000 picture elements on a raster scan display screen 80 alphanumeric characters per line and 25 lines HORIZONTAL AND VERTICAL RESOLUTION Horizontal resolution is defined in terms of the number of picture elements that can be displayed on the horizontal line without overlapping or running into each other It is often stated in terms of lines of resolution In other words a monitor with a horizontal resolution of 1 000 lines can display 1 000 vertical lines using 1 000 picture elements per line Vertical resolution depends on the number of horizontal scan lines used by the particular display raster Generally the greater the number of scan lines the easier it is to re
202. t uses 1 000 picture elements per line with a horizontal resolution of 1 000 can display what total number of vertical lines 1 10 2 100 3 1 000 4 10 000 A raster frame is displayed approximately how many times a second 1 5 2 10 3 20 4 30 To reduce the depth of crt caused by the length of the tube what type of displays were designed 1 Wide panel 2 Flat panel 3 Narrow panel 4 Short panel 2 73 Compared to the gas plasma and 2 74 The operation of an electroluminescent electroluminescent displays a liquid display requires what total number of crystal display differs in which of the volts following ways 1 5 1 It does not use as many picture 2 10 elements 3 15 2 It does not use a light for the picture 4 20 elements 3 It does not generate its own light for the picture elements 4 It does not have a backlight 14 3 3 4 ASSIGNMENT 3 Textbook assignment Chapter 3 Software pages 3 1 through 3 29 What must you load into a computer to manage its resources and operations Bootstrap program Word processor Graphics program Operating system eU ICE What program controls the execution of other programs according to job information 1 An operating system 2 A bootstrap program 3 A word processor 4 Autility program The simplest and most commonly used operating systems on microcomputers are which of the following types Multiuser single tasking Si
203. taining stock number the name of the item its unit price the quantity on hand and its bin location FILE A collection of related records such as the payroll or supply inventory records Normally all records within the file are in the same format When processing data we think in terms of data files For example to process a parts inventory you would need the master parts inventory file and the file that contains up to date information on each part that has been issued The master parts inventory file would have a record for every part in the inventory The update file parts issued file would have a record for each part issued You would use a program to read the records on the parts issued file and update the matching records on the master parts inventory file Depending on whether the data is stored on magnetic tape or disk or in internal storage the program would use different methods to access storage to obtain the data In the next section you ll learn about storage access methods 4 14 15 What area in the computer s primary storage area holds the processing instructions the program Q 16 How are the boundaries determined for the separate areas of the computer s primary storage area Q 17 What is a bit Q 18 How many bits make up a byte Q 19 Primary storage capacities are usually specified in what unit of measure Q 20 How are core planes formed Q 21 Where are core planes used Q 22 Who designs and builds th
204. te the need for programmers to write new programs when all they want to do is copy print or sort a data file which of the following types of programs can be used 1 Word processor 2 Graphics 3 Utility 4 Spreadsheet What is the term given to arranging records in a predefined sequence or order 1 Sorting 2 Merging 3 Writing 4 Shifting On a computer what is the sequence of characters called Numerical sequence Collating sequence Random sequence Alphabetic sequence TA To sort a data file what must you tell the sort program How many characters are in the file How many records are in the file The length of the data file The data field or fields to sort on Ta 16 3 14 3 15 3 16 3 17 Sort merge programs usually have which of the following characteristics 1 Specific file length 2 Specific run time 3 Phases 4 Names What personnel or methods are used to generate programs to print detail and summary reports of data files Programmers Operating systems Sort merge programs Report program generators Boer What are report program generators designed to save 1 Runtime 2 Programming time 3 Operator time 4 Printer time Each time there is a control break what does the program developed by the report program generator print Input information Output information Summary information Programming information Mus a a A computer language th
205. ter 2 you should be feeling more at ease with digital computers You should realize by now that they are not so hard to understand once you have the terminology down The information that follows summarizes the important points of this chapter The CENTRAL PROCESSING UNIT is the brain of the computer We generally refer to it as the cpu or mainframe The CONTROL SECTION directs the flow of traffic operations and data and maintains order within the computer The ARITHMETIC LOGIC SECTION performs all arithmetic operations adding subtracting multiplying and dividing It also tests various conditions during processing and takes action based on the result INTERNAL STORAGE is sometimes referred to as primary storage main storage or main memory because its functions are similar to our own human memory It stores the programs and data MAGNETIC CORE STORAGE is made up of tiny doughnut shaped rings made of ferrite iron that are strung on a grid of very thin wires SEMICONDUCTOR STORAGE consists of hundreds of thousands of tiny electronic circuits etched on a silicon chip BUBBLE STORAGE is made of semiconductor material in the form of a very thin crystal READ ONLY MEMORY ROM allows us to permanently store programs that will not be lost even when the computer is powered down RANDOM ACCESS MEMORY RAM is read write memory It is the working memory rather like a blackboard that you can scribble down notes read them and rub t
206. the program from a keyboard console intervention by the operator FOURTH GENERATION AND BEYOND The computers of the fourth generation are not easily distinguished from earlier generations yet there are some striking and important differences The manufacturing of integrated circuits has advanced to the point where thousands of circuits active components can be placed on a silicon wafer only a fraction of an inch in size the computer on a chip This has led to what is called large scale integration LSI and very large scale integration VLSI As a result of this technology computers are significantly smaller in physical size and lower in cost Yet they have retained large memory capacities and are ultra fast Large mainframe computers are increasingly complex Medium sized computers can perform the same tasks as large third generation computers An entirely new breed of computers called microcomputers fig 1 9 and minicomputers are small and inexpensive and yet they provide a large amount of computing power 1 12 CRT DISPLAY SCREEN aw DRIVE DISK SIME TII KEYBOARD Figure 1 9 Fourth generation desktop personal computer What is in store for the future The computer industry still has a long way to go in the field of miniaturization You can expect to see the power of large mainframe computers on a single super chip Massive data bases such as the Navy s supply system may be written into read only memo
207. the read write head assembly making contact with the heads The magnetic tape unit reads and writes data in parallel channels or tracks along the length of the tape as shown in figure 2 19 view A Each channel or track is used by a read write head one for each channel as the tape moves across the magnetic gap of the head Read write heads may be either one gap or two gap as shown in figure 2 19 views B and C The one gap head has only one magnetic gap at which both reading and writing occur The two gap head has one gap for reading and another for writing Although the one gap is satisfactory the two gap head gives increased speed by checking while writing For example a tape being written on passes over the write gap where the data is recorded and then the data is read as it passes over the read gap to make a comparison With this method errors are detected almost instantly When you look closely at figure 2 19 view B top view you will notice that there is one read write coil in the write head for each channel or track In this particular case there are seven It is the electrical current flowing through these coils that magnetizes the iron oxide coating on the surface of the tape 2 19 SUPPLY REEL TAKE UP REEL READ WRITE HEAD ASSEMBLY Figure 2 18 A basic tape drive mechanism 2 20 RECORDS A f TAPE MOTION SEVEN TRACK ah o gt ONE GAP READ WRITE HEAD VIEW FROM TOP TAPE GAP PLA
208. tions such as SNAP II user terminals and desktop computers 2 28 The raster is a series of horizontal lines crossing the face of the crt screen fig 2 28 Each horizontal line is made up of one trace of the electron beam from left to right The raster starts at the top left corner of the crt screen As each horizontal line is completed the blanked electron beam is rapidly returned or retraced to the left of the screen START HORIZONTAL SWEEP RETRACE BLANKED VERTICAL N RETRACE BLANKED END SWEEP NOTE REMEMBER IN REALITY THESE LINES ARE PACKED TIGHTLY TOGETHER THEY ARE SPREAD OUT IN THIS ILLUSTRATION ONLY TO GIVE YOU AN IDEA OF HOW THEY ARE DEFLECTED Figure 2 28 Raster or TV scan Vertical deflection moves the beam down and the horizontal sweep repeats When the vertical sweep reaches the bottom line of the raster a vertical blanked retrace returns the sweep to the starting position of the raster and the process is repeated Each completed raster scan is referred to as a field two fields make up a frame The display rate of fields and frames determines the amount of flicker in the display that is perceived by the human eye Each field is made up of approximately 525 horizontal lines The actual number of horizontal lines varies from device to device A frame consists of the interlaced lines of two fields The horizontal lines of the two fields are interlaced to smooth out the display A display rate of 30 frames p
209. to set up a table of rows and columns and specify what calculations to perform on the columns You enter values for the basic information into the appropriate rows and columns Then the processor performs the calculations In our example fig 3 10 we used a spreadsheet to project magnetic media costs You enter the item descriptions column headings report title and data for columns 1 2 and 4 and the software calculates column 3 by adding columns 1 and 2 Then it multiplies column 3 times column 4 and puts the result in column 5 It also subtotals and totals the columns you specify in this case columns 1 through 3 and column 5 3 25 TAPES DISKS DISKETTES 3a SUBTOTAL TOTAL MAGNETIC REQUIREMENTS NUMBER TO EE REPLACED 1 a ar a 20 33 SPREAD SHEET NUMIBER FOR EXPANSION 2 ae f AA ao 0 115 ITALICS DATA YOU ENTER BOLD INFORMATION CALCULATED BY THE PROGRAM GRAPHICS Graphics capability is available on many microcomputers One use is to produce data displays like bar charts pie charts and graphs See figure 3 11 view A and view B On some micros you can do line drawings on others you can create sophisticated engineering drawings High resolution color graphics are COST PER TEM 4 SRG FONT Figure 3 10 Spreadsheet example also available for specialized applications NAP A PIE CHART Figure 3 11A Graphics examples PIE CHART
210. tored contain only three or four characters then many of the storage positions in each word are not being used Fixed word length computers have faster calculating speeds They can add two data words in a single operation This is not so with character addressable computers Here only one digit byte in each number can be added during a single machine operation Thus eight steps are required to complete the calculation The larger mainframe computers super computers like the CRAY 1 and CYBER 205 use only fixed word length storage Most microcomputers use the variable word length approach allowing them to operate on one character at a time Somewhere in between these two extremes are the dozens of existing minicomputer and mainframe models that have what is called built in flexibility These flexible computers are byte oriented but can operate in either a fixed or variable word length mode through the use of proper program instructions Let s take a look at how these flexible computers operate in a variable and fixed word length environment Working in a variable word length environment each address holds one alphanumeric character as shown in figure 4 9 view B Since a byte usually represents a single alphanumeric character unless you are using packed decimal a flexible computer is often said to be byte addressable Don t become confused the terms character addressable character oriented and byte addressable all have the same meaning B
211. tored program computer where is the overflow stored Input storage area Output storage area Primary memory Auxiliary memory Tu 2 6 2 7 2 8 2 10 What part of the computer dictates how and when each specific operation is to be performed 1 Control section 2 Arithmetic logic section 3 Input storage area 4 Output storage area Of the four major types of instructions which one has the basic function of moving data from one location to another 1 Control 2 Logic 3 Arithmetic 4 Transfer To send commands to devices not under direct command of the control section what type of instructions are used 1 Control 2 Logic 3 Arithmetic 4 Transfer Operations like adding and multiplying are performed by what section Control logic Storage logic Arithmetic logic Transfer logic Se ca When processing is taking place data is transferred back and forth between what two sections Control and internal storage Internal storage and arithmetic logic Control and arithmetic Arithmetic and output 2 11 2 12 2 13 2 14 2 15 The process by which instructions and data are read into a computer is called what 1 Moving 2 Storing 3 Inputting 4 Loading An auxiliary wired memory is used in some computers to permanently store a small program that makes manual loading unnecessary What is this program called 1 Operating system 2 Bootstrap 3
212. tronic digital computers 1 5 Figure 1 4 Electronic digital computer SPECIAL PURPOSE COMPUTERS A special purpose computer as the name implies is designed to perform a specific operation and usually satisfies the needs of a particular type of problem Such a computer system would be useful in weather predictions satellite tracking or oil exploration While a special purpose computer may have many of the same features found in a general purpose computer its applicability to a particular problem is a function of its design rather than to a stored program The instructions that control it are built directly into the computer which makes for a more efficient and effective operation A drawback of this specialization however 1s the computer s lack of versatility It cannot be used to perform other operations GENERAL PURPOSE COMPUTERS General purpose computers are designed to perform a wide variety of functions and operations You will probably use this type of computer A general purpose computer is able to perform a wide variety of operations because it can store and execute different programs in its internal storage Unfortunately having this ability is often achieved at the expense of speed and efficiency In most situations however you will find that having this flexibility makes this compromise a most acceptable one ANALOG CO
213. tware We refer to the machines that compose a computer system as hardware This hardware includes all the mechanical electrical electronic and magnetic devices within the computer itself the central processing unit and all related peripheral devices printers magnetic tape units magnetic disk drive units and so on These devices will be covered in this chapter to show you how they function and how they relate to one another Take a few minutes to study figure 2 1 It shows the functional units of a computer system the inputs the central processing unit cpu and the outputs The inputs can be on any storage medium from punched cards paper tape or magnetic ink to magnetic tape disk or drum or they can be entries from a console keyboard or a cathode ray tube crt terminal The data from one or more of these inputs will be processed by the central processing unit to produce output The output may be in punched cards or paper tape on magnetic tape disk or drum or it may be printed reports or information displayed on a console typewriter or crt terminal The figure also shows the data flow instruction flow and flow of control We ll start our hardware discussion with the cpu and then move into storage media disk tape and drum We ll end the chapter with a discussion of input output devices and how they work CENTRAL PROCESSING UNIT CPU The brain of a computer system is the central processing unit which we generally refer to as the
214. urce often called a backlight for computer applications The liquid crystal material between the charged electrodes becomes translucent when voltage is applied and allows the backlight to shine through as a picture element In the gas plasma and electroluminescent displays the picture element light is generated by ionizing a gas neon or neon argon between the charged electrodes gas plasma display or by stimulating a luminescent material in the same manner electroluminescent display In either case the picture element only emits light when the electrodes have voltage applied to them One of the advantages of flat panel displays is that smaller voltages are required for their operation than for a crt Gas plasma displays use approximately 200 volts to charge the electrodes and electroluminescent displays require only 20 volts The picture elements in these displays are addressed by the row and column method Displays with as many as 737 280 picture elements 960 rows by 768 columns have been developed The picture elements on flat panel displays are not lighted continually This would require a large amount of power and generate excessive heat A sequential scan similar to a crt raster is used Once again a page memory is required The picture element electrodes are on and off as the scan sequentially addresses page memory Those picture elements that are to display a dot are momentarily turned on and off starting with the first picture e
215. ure that any data lost can be recovered ule Records Backup files Tracks Blocks 1 55 What two media are commonly used for 1 56 backup 1 Paper tape and punched cards 2 Magnetic tape and punched cards 3 Disk and magnetic tape 4 Disk and drum What is the most common method of creating a backup for a microcomputer 1 2 3 Copying the disk onto a magnetic tape Copying the disk onto a paper tape Copying the disk onto a punched card Copying the disk onto another disk 2 1 2 2 2 3 2 5 ASSIGNMENT 2 Textbook assignment Chapter 2 Hardware pages 2 1 through 2 35 The components or tools of a computer system can be grouped into what two categories Hardware and software Hardware and firmware Firmware and software Software and programs eS et Er What section unit is the brain of a computer system Control section Arithmetic logic section Central processing unit Input unit Burgo What section unit is the computing center of a computer system Arithmetic logic section Central processing unit Control section Output unit roD The central processing unit is made up of which of the following sections 1 Control and internal storage only Central and arithmetic logic only 3 Arithmetic logic and internal storage only 4 Control internal storage and arithmetic logic When a program is so large and complex that it exceeds the memory capacity of a s
216. urse and while using technical manuals associated with the equipment you will be working on you will find the below notations at the end of some paragraphs The notations are used to emphasize that safety hazards exist and care must be taken or observed WARNING AN OPERATING PROCEDURE PRACTICE OR CONDITION ETC WHICH MAY RESULT IN INJURY OR DEATH IF NOT CAREFULLY OBSERVED OR FOLLOWED CAUTION AN OPERATING PROCEDURE PRACTICE OR CONDITION ETC WHICH MAY RESULT IN DAMAGE TO EQUIPMENT IF NOT CAREFULLY OBSERVED OR FOLLOWED NOTE An operating procedure practice or condition etc which is essential to emphasize vi INSTRUCTIONS FOR TAKING THE COURSE ASSIGNMENTS The text pages that you are to study are listed at the beginning of each assignment Study these pages carefully before attempting to answer the questions Pay close attention to tables and illustrations and read the learning objectives The learning objectives state what you should be able to do after studying the material Answering the questions correctly helps you accomplish the objectives SELECTING YOUR ANSWERS Read each question carefully then select the BEST answer You may refer freely to the text The answers must be the result of your own work and decisions You are prohibited from referring to or copying the answers of others and from giving answers to anyone else taking the course SUBMITTING YOUR ASSIGNMENTS To have your assignments grad
217. use of pictorial means to present data in the form of plotted curves graphs bar pie line and so on or diagrams These may be displayed on a crt or printed AI 4 HANDSHAKING The process through which the rules for exchanging data over a communications line are defined for the two devices involved HARD COPY The term given to humanly readable printed output from a computer HARDWARE The visible physical equipment of a system including the computer cpu and related peripheral equipment as distinguished from software HEAD POSITIONING Placing a read write head over a specified track on a disk or drum HEXADECIMAL The number system with base 16 0 9 and A F A represents 10 B represents 11 C represents 12 D represents 13 E represents 14 and F represents 15 Used in some computer systems HIGH LEVEL LANGUAGES Programming languages that allow the programmer to write programs in English like terms and symbols and mathematical notation rather than the O s and 1 s used by the computer These high level programs must be translated into machine language before the computer can execute them FORTRAN Ada COBOL and BASIC are examples HOST COMPUTER The main or controlling computer in a distributed data processing network ddp HYBRID COMPUTER A computer that combines the functions of both analog and digital computers I O Input Output INPUT The data entered into a computer system for processing INPUT DEVICE
218. using 8 bit EBCDIC code Since one numeric character can be represented and stored using only four bits 8 4 2 1 using an 8 bit code allows the representation of two numeric characters decimal digits as illustrated in figure 4 6 Representing two numeric characters in one byte eight bits is referred to as packing or packed data By packing data numeric characters only in this way it allows us to conserve the amount of storage space required and at the same time increases processing speed 4 5 DECIMAL VALUE 9 2 7 3 EBCDIC CODE 1001 0010 0111 0011 BIT PLACE VALUES 8421 8421 8421 8421 BYTE 1 BYTE 1 Figure 4 6 Packed data AMERICAN STANDARD CODE FOR INFORMATION INTERCHANGE ASCII Another 8 bit code known as the American Standard Code for Information Interchange ASCII pronounced ASS KEY was originally designed as a 7 bit code Several computer manufacturers cooperated to develop this code for transmitting and processing data The purpose was to standardize a binary code to give the computer user the capability of using several machines to process data regardless of the manufacturer IBM HONEYWELL UNIVAC BURROUGHS and so on However since most computers are designed to handle store and manipulate 8 bit code an 8 bit version of ASCII was developed ASCII is commonly used in the transmission of data through data communications and is used almost exclusively to represent d
219. uter Q 6 What does the acronym EBCDIC stand for Q 7 By using an 8 bit code how many characters or bit combinations can be represented Q 8 What is the base of a hexadecimal number system Q 9 What term is used for the representation of two numeric characters stored in eight bits Q 10 What does the acronym ASCII mean 11 What was the purpose of several computer manufacturers cooperating to develop ASCII code for purp processing and transmitting data Q 12 Are there any differences in the concepts and advantages of ASCII and EBCDIC Q 13 How is the parity bit in each storage location used Q 14 A computer or device that uses 8 bit ASCII or EBCDIC will use how many bits to store each character DATA STORAGE CONCEPTS You learned in chapter 2 that a computer s primary storage area is divided into four areas each serving a specific purpose The input storage area accepts and holds input data to be processed The working storage area holds intermediate processing results The output storage area holds the final processing results The program storage area holds the processing instructions the program You also learned that these separate areas do not have built in physical boundaries rather the boundaries are determined by the individual programs being used You also may recall in chapter 2 we talked about the different types of primary storage used in computers and how they differ from one another Some were magnetic in natur
220. y using the appropriate program instructions a programmer can retrieve a stored data element by identifying the address of the first character say position 300 as in fig 4 9 view B and specifying the number of address locations to be included in the word In this case there are seven positions 300 through 306 When a flexible computer is working in a fixed word length environment each address identifies a group of bytes that can be operated on as a unit This processing method helps to achieve faster calculating speeds A programmer can use program instructions to cause the computer to automatically retrieve manipulate and store as a unit a fixed word of say two four or eight bytes of data in one machine operation by identifying the address of the first character of data At the same time all remaining bytes are acted upon as a unit moving from left to right Figure 4 10 illustrates the different word lengths possible with many byte addressable computers They are half word 2 bytes full word 4 bytes and double word 8 bytes 4 12 i 1 BYTE 1 CODED ALPHANUMERIC CHARACTER NORMALLY amp BITS IN LENGTH FIXED HALF wORD REPRESENTS HALF OF COMPUTER 2BYTES WORD FOR ADDRESSING PURPOSES AX 4 UNIT OF STORAGE USED ON MANY MICROCOMPUTERS 16 BITS IN LENGTH FIXED REPRESENTE FULL COMPUTER WORD FOR ADDRESSING PURPOSES UNT OF STORAGE USED MOSTLY ON MAINFRAME COMPUTERS r38 BITS IM
221. you ruin will invariably contain the most important data on that disk Storage Never bend fold or otherwise distort the shape of a disk Never place heavy objects such as books on top of disks Store disks in the box they came in or in filing containers that are specifically designed for storing disks Try to store disks vertically but if you do store disks horizontally do not stack more than 10 disks Exposure Disks are subject to exposure from magnetic fields smoke heat and sunlight X rays may also have a negative effect MAGNETIC FIELDS Disks should never be exposed to anything that could be the source of a magnetic field Exposure of a disk to a magnetic field could cause the destruction of some or all of the data contained on that disk Some common sources of magnetic energy are crt s disk drives and perhaps the most common the telephone SMOKE Smoke can cause buildup on disks and on disk drives DO NOT SMOKE while you work at a terminal or computer 1 20 HEAT AND SUNLIGHT Never expose disks to excessive heat or direct sunlight Either can cause the disks to become warped or distorted so they cannot be used Disks are made of a plastic material and 1f you have ever seen a phonograph record that has been exposed to heat or sunlight you have some idea of the damage that can result from exposure Typically disks will operate only between 10 and 50 degrees Celsius 50 to 120 degrees Fahrenheit They will accept a

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