User Manual - Programmer`s Heaven User Uploaded Files
Contents
1. not allocate multiple sectors into one allocation unit it uses each individual sector as one allocation unit This method wastes less disk space Comparing BDFS to the other major file systems shows the increased level of efficiency that BDFS brings to the PC platform NTFS FAT HFS and EXT 2 group several physical disk sectors into a single unit called a Cluster Disk Size Cluster Size Physical Disk Sectors 1 025 MB 2 GB 2 KB 4 2 GB 2 terabytes 4 KB 8 If a single text file is 50 bytes long it will take up one cluster since the system sees one cluster as the smallest addressable unit of storage If you have a modern 20 GB hard drive with NTFS and this 50 byte text file is stored on the disk you have 3 950 bytes 8 physical sectors that contain no usable data and cannot be allocated to anything besides the 50 byte text file The more small files you have on the disk the larger the wasted space becomes BDFS fixes this problem by using Logical Sector Numbers to keep track of each physical disk sector Taking the 50 byte text file and 20GB hard drive from the previous example we can compute the amount of wasted space that BDFS will allow Since each Logical Sector Number is 512 bytes and is the smallest addressable unit of storage there is a total of 462 bytes wasted NTFS FAT HFS and EXT 2 waste 3 950 bytes per every 50 bytes and BDFS wastes 462 bytes per every 50 bytes which means Exacta wastes 88 less disk space than Microsof2. the application programming interface Any programmer can use the above interrupt definitions when writing a program to accomplish a task the core kernel provides The kernel accomplishes memory management in a very simple way since this version runs in 16 bit Real Mode The first segment of memory available is held in a variable that the kernel will modify when a program attempts to load Whena program exits the kernel will decrease the variable by the same size that was requested when the program first ran Memory management will be a larger factor when the Exacta operating system is run in 32 bit Protected Mode Exacta 4 0 changed the way file handling is controlled There are four file handles to which an Open File call will assign to the operation The only contents of this file handle are the File Table entry offset value There is another kernel function that controls outputting the contents of the entry Command Line Interface The Exacta Command Line Interface CLI takes user input transfers it to the core kernel in terms of Interrupts receives the core kernel output and translates it into user friendly terminology The user prompt most commonly identifies a command line interface Microsoft DOS has a default prompt of C gt which in turn can be customized by the user UNIX LINUX operating systems have different command line interfaces that are called shells A Bash shell has a user prompt of gt and various other shells The Exa
3. Exacta Operating System Version 4 0 V ECTRASOFT A Division Of Vectra Enterprises Created By Robert Svec Conceived On J une 22 2005 Copyright 2005 2007 Vectra Soft February 18 2007 Section 1 Part Part II Part III Part IV Contents Introduction Description Basic Disk File System Core Kernel Command Line Interface Page 3 Page 4 Page 5 Page 7 Page 14 Introduction An operating system designed for an IBM compatible PC must include the following four things I O Control File System Memory Management and an Application Programming Interface API These four characteristics are the absolute minimum requirements for a program to be defined as an operating system As most PC users know Microsoft Windows the most common operating system This operating system has advanced I O Control in the form of being able to use any type of I O device available on the market keyboard mouse printer USB devices CD ROM drives etc The simplest I O devices are the keyboard input and monitor output The Exacta operating system utilizes these two I O functions The older DOS and Windows 9x operating systems had a file system called the File Allocation Table FAT The new Windows 2000 XP uses a file system called New Technology File System NTFS These file systems provide data organization on a disk which can be anything including a floppy disk hard drive or CD ROM The Exacta operating system uses the Basic Disk File Sy
4. ble PCs such as FAT Windows 9x NTFS Windows XP HFS Mac OS X UNIX and EXT 2 Linux UNIX The file system takes up space on the disk so the most compact way to store all the information in the database is a large factor of efficiency Since the operating system kernel will control file routines such as create file open file read file and write file the database structure needs to be set up in a way the kernel can easily access the data structures modify them and create new entries Disks store data in physical sectors that can hold 512 bytes The actual geometry of the disk is quite complicated and in turn creates a problem for a file system to accurately manage each and every sector Here is a diagram of a physical floppy disk Breakdown Identifiers 18 Sectors Per Track 1 18 80 Tracks Per Head 0 79 2 Heads 0 1 A file system typically uses a logical numeric method to keep track of the physical sectors This is known as a Logical Sector Number LSN An example of a LSN and a physical sector is below Logical Physical LSN 1 Sector 2 Track 0 Head 0 LSN 17 Sector 18 Track 0 Head 0 LSN 18 Sector 1 Track 0 Head 1 LSN 2879 Sector 18 Track 79 Head 1 To make this structure easier to use a typical file system will group several physical disk sectors into one organizational unit called an allocate block and keep track of each allocation block rather than each individual physical disk sector Basic Disk File System BDFS does
5. cta CLI is called the Aurora Prompt This is what the Aurora Prompt looks like Prompt Location gt Root BIN gt Bin folder under root BIN SYSTEM gt System folder under Bin The current directory and its path are displayed and always in capital letters The pound sign shows that this is the Exacta Aurora Prompt There are several commands that the CLI provides which are outlined below Command Parameters Function Ver N A Displays version info Dir N A Displays all files and folders In current directory Mkdir lt directory name gt Create Directory in current Directory Rmdir lt directory name gt Remove directory in current Directory Show lt file name gt Display contents of a text file On screen Drive Oorlor2 0 15 Floppy 1 2 Floppy 2 15 Hard Drive 3 2 Hard Drive If no parameters current drive Will be displayed Help N A Displays commands and syntax Del lt file name gt Remove file under current directory Rename lt file name gt Change file name of a file under Current directory Mem N A Display Free Memory Segment Handles N A Display File Handle data Label N A Changes Current Drive Label NOTE all commands are in lower case The CLI also allows the user to run programs You can type in the full program name or omit the com extension to run a specific program Once the program exits you will be back into the CLI Future command line interfaces will display the operating system different
6. e more efficient in the two most important functions of an operating system the File System and Memory Management Description The Exacta operating system runs on an IBM compatible PC with an Intel x86 CPU All versions of Exacta run in 16 bit Real Mode typically on a 1 44MB floppy disk Applications are flat binary linear execution files commonly known in the Microsoft world as com executables Exacta will run any Microsoft com executable as long as all of the interrupts are available in Exacta Version 4 0 optimizes all functions of the 3 x series as well as provides improved error handling and reduced external applications bundled with the installation Complete with a Kernel and a Command Line Interface Exacta allows complete freedom of usage and expansion This publication will list all available API functions and known processes for complete user customization of the operating system The ability of any programmer to assist in the evolution of the operating system is the main reason Exacta was written Basic Disk File System A file system organizes data on a hard drive into files for users to access and modify Utilizing the most of the hard drive is the ultimate goal of a file system How well a file system organizes data as well as utilizing the most of the disk possible determines how efficient the file system is There are a few major file systems that exist today that are used by the common operating systems for IBM compati
7. imal to ASCII character INPUT OUTPUT NOTES ES DI segment offset of buffer DX hex character ES DI terminated ASCII string AH 7 Load Byte From File Table INPUT OUTPUT NOTES SI Offset in File Table AL Byte This function will read the next File Table sector into memory if needed AH 8 Read Logical Sector INPUT OUTPUT NOTES DX Logical Sector Number BP BX segment offset of buffer AX 0 Successful AX 1 Disk Read Error Make sure your buffer is 512 bytes AH 9 Write Logical Sector INPUT OUTPUT NOTES DX Logical Sector Number BP BX segment offset of buffer AX 0 Successful AX 1 Disk Write Error Make sure your buffer is 512 bytes AH OAh Set Text Color INPUT AL Color OUTPUT N A NOTES Color Table Low 4 bits set foreground color High 4 bits set background color BIN 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 COLOR black blue green cyan red magenta brown light gray dark gray light blue light green light cyan light red light magenta yellow white Example 1110000b White background black text AH OBh Reset File Table Sectors INPUT N A OUTPUT NOTES First File Table Sector loaded into memory AH OFFh Shutdown System INPUT N A OUTPUT NOTES Restart kernel code Pressing Enter will restart kernel This interrupt I O is also
8. k of the directory numbers Itis 254 bytes long which is less than one disk sector The value of each byte is either 0 which means the directory number is free or 1 which means that directory number is taken There is a maximum number of 254 directories in each file system until future versions increase the table to 2 byte and 4 byte values Kernel The Exacta Kernel Version 4 0 has four main goals Provide efficient I O functions efficient memory management efficient file system functions and an efficient application programming interface The Exacta Kernel currently supports Interrupt I O from applications as well as some minute keyboard input and monitor output The Kernel creates interrupt 20h and 21h Interrupt 21h is identical to Microsoft DOS in syntax for compatibility but Interrupt 20h is defined for Exacta operation The complete Interrupt reference is contained below Interrupt 21h AH 1 Character Input from Keyboard INPUT N A OUTPUT AL Character received AH 2 Character Output to Screen INPUT AL ASCII Character OUTPUT Character on screen AH 9 Print String INPUT DS DX segment offset of terminated string OUTPUT string printed on screen AH A Buffered Input INPUT DS DX segment offset of buffer OUTPUT Character from keyboard stored in DS DX DX Incremented NOTES Maximum size 65 536 bytes AH 30h Get Kernel Version INPUT ES DX segment offset of input string buffe
9. ly and have different functions as well The kernel looks for a file named cli com upon boot and loads that into memory so you could write your own CLI and replace the Aurora Prompt CLI with your own There are a few rules that need to be followed by the user since there are no rule checking procedures in this version You cannot have two files with the same filename This will cause a huge problem when it comes time to access them by reading writing or deleting Do not create a file with the same name as a CLI command The internal commands described above have precedence over the external files and applications so if you created your own program that plays Blackjack and you save it as handles you will never be able to run this application because the internal handles command will execute before a search for an external file is performed The CLI offers the execute bat function which is an automatic script that will run a program before the command prompt is displayed This is the same concept as the MS MS DOS autoexec bat file You can create the execute bat file by running edit com and typing the filename you want to run on boot followed by a carriage return new line Save the file as execute bat press Escape to exit the operating system and reboot After the welcome message the program you listed will execute and when it finishes the command prompt will appear To remove this function just delete the execute bat file
10. r OUTPUT DH Major DL Minor AH 3Ah Remove Directory INPUT DS DX segment offset of terminated directory name OUTPUT AX 0 Success NOTES Removes directory only if it is under current directory AH 3Ch Create File INPUT DS DX segment offset of terminated filename OUTPUT AX 0 Success NOTES Creates file in current directory size 0 bytes AH 3Dh Open File INPUT AL mode 0 DS DX segment offset of terminated filename OUTPUT AX File handle BP Segment where file contents are located NOTES Opens file under current directory only AH 39h Create Directory INPUT DS DX segment offset of terminated directory name OUTPUT AX 0 Success NOTES Creates directory under current directory AH 40h Write File INPUT BX handle CX of bytes to read DS DX segment offset of buffer OUTPUT AX 0 Success NOTES AH 48h Allocate Memory INPUT BX Number of paragraphs to allocate bytes 16 OUTPUT AX Segment of allocated memory NOTES Offset is always 0 AH 49h Release Memory INPUT CX Number of bytes to release OUTPUT N A NOTES AH 4Bh Execute Program INPUT DS DX segment offset of filename OUTPUT Jump to program code NOTES Filename does not need to be in current directory AH 4Eh Find File INPUT DS DX segment offset of terminated filename OUTPUT AX 0 Success BX Starting Block or Directory Number CX Size FFFF if di
11. rectory DH Directory file located in BP File Table offset of entry beginning AH 3Eh Close File INPUT BX Handle OUTPUT AX 0 Success NOTES Kernel File handle variable is cleared Kernel Memory is released AH 41h Delete File INPUT DS DX segment offset of terminated filename OUTPUT AX 0 Success NOTES File must be under current directory AH 25h Set Interrupt Vector INPUT DS DX segment offset of new handler code AL Interrupt number OUTPUT AX 0 Success NOTES AH 35h Get Interrupt Vector INPUT AL Interrupt number OUTPUT AX BX segment offset of handler code NOTES AH OEh Set Current Drive INPUT DL Drive OUTPUT AX 0 Success NOTES AH 19h Get Current Drive INPUT N A OUTPUT AL Drive NOTES Interrupt 20h AH 0 Terminate Program INPUT N A OUTPUT Resets registers and restarts kernel code NOTES Use RET command in a COM executable to return to CLI AH 1 Read File system INPUT N A OUTPUT AX 0 Success NOTES AH 2 Write File system INPUT N A OUTPUT AX 0 Success NOTES AH 3 Get Free Segment INPUT N A OUTPUT DX Free segment NOTES Offset is always 0 AH 4 Get File handle information INPUT AL File Handle OUTPUT BX Starting LSN Block CX Size DH Directory BP File Table Offset NOTES AH 5 Next free LSN INPUT N A OUTPUT DX Free LSN NOTES AH 6 Convert Hexadec
12. stem version 16 Memory Management is the organization and utilization of RAM The most common CPU is the Intel x86 Architecture CPU ex Pentium 4 This CPU can access up to 4GBs of RAM using 32 bit operation codes An operating system needs to make sure this possible 4GB of RAM is organized protected and properly utilized by applications The old days of Microsoft DOS had quite a bit of user level memory managers such as drivers like HIMEM SYS and EMM386 EXE but the current Microsoft technology takes care of memory management in the background An Application Programming Interface is simply a way for programmers to write applications that use functions provided by the operating system There are many ways in which a modern operating system provides an API one of which is called the Interrupt Microsoft DOS provided an API through Interrupt 21h and 20h Functions that programmers can access via interrupt API include Create File Open File Run Program etc If the operating system does not provide a good API then programmers cannot create applications that utilize the operating system functions Exacta uses the same interrupt scheme as Microsoft DOS which allows programs written for Microsoft DOS to be compatible with Exacta As stated earlier an operating system needs to have these four parts The only thing that distinguishes a good operating system from a bad one is the amount of efficiency each of the four parts The goal of Exacta is to becom
13. t The BDFS file system is broken down into three databases the File Table Location Block and an optional Directory Table The File Table holds 16 byte entries for each file and directory hence it is BDFS version 16 The breakdown of the File Table entry is below AAAAAAAAAAABBCCD Filename 11 characters Location Block if file Directory Number if directory Size in bytes if file FFFFh if directory Directory file or directory resides in A B C D Since each entry is 16 bytes and the maximum number of Location Blocks usable for files is 65 532 and the maximum number of directories is 254 there is a maximum of 65 786 entries The maximum number of disk sectors the File Table takes up is 129 which makes the maximum File Table size 66Kb The Location Block is a database that tracks each disk sector for file allocation The values for a Location Block are listed below Value Definition 0000h Free FFFEh Reserved FFFFh End of entry 0001h FFFDh Pointer to next block Since each block equals one disk sector 512 bytes and a maximum of 65 532 blocks limits BDFS to a maximum amount of storage 32MB which is extremely less than other file systems The only limiting factor is the 2 byte length of the allocation block Future Exacta file systems will be 32 bit which will bring the maximum storage value over 2 Terabytes The Location Block takes up 128 disk sectors which makes the maximum size 65 5Kb The Directory Table keeps trac
Download Pdf Manuals
Related Search