_ _ ____ _____ | | | | / __ \ / ____| | |__ ___ ___ | |_| | | | (___ | '_ \ / _ \ / _ \| __| | | |\___ \ | |_) | (_) | (_) | |_| |__| |____) | |_.__/ \___/ \___/ \__|\____/|_____/ bootOS operating system in 512 bytes (boot sector) by Oscar Toledo G. Jul/22/2019 http://nanochess.org https://github.com/nanochess/bootOS It's compatible with 8088 (the original IBM PC). If you want to assemble it, you must download the Netwide Assembler (nasm) from www.nasm.us Use this command line: nasm -f bin os.asm -l os.lst -o os.img What is bootOS: bootOS is a monolithic operating system that fits in one boot sector. It's able to load, execute, and save programs. Also keeps a filesystem. It can work with any floppy disk size starting at 180K. It relocates itself at 0000:7a00 and requires further 768 bytes of memory starting at 0000:7700. This operating system runs programs as boot sectors at 0000:7c00. It provides the following services: int 0x20 Exit to operating system. int 0x21 Input key and show in screen. Entry: none Output: AL = ASCII key pressed. Affects: AH/BX/BP. int 0x22 Output character to screen. Entry: AL = Character. Output: none. Affects: AH/BX/BP. int 0x23 Load file. Entry: DS:BX = Filename terminated with zero. ES:DI = Point to source data (512 bytes) Output: Carry flag = 0 = Found, 1 = Not found. Affects: All registers (including ES). int 0x24 Save file. Entry: DS:BX = Filename terminated with zero. ES:DI = Point to data target (512 bytes) Output: Carry flag = 0 = Successful. 1 = Error. Affects: All registers (including ES). int 0x25 Delete file. Entry: DS:BX = Filename terminated with zero. Affects: All registers (including ES). Filesystem organization: bootOS uses tracks from 0 to 32, side 0, sector 1. The directory is contained in track 0, side 0, sector 2. Each entry in the directory is 16 bytes wide, and contains the ASCII name of the file finished with a zero byte. A sector has a capacity of 512 bytes, it means only 32 files can be kept on a floppy disk. Deleting a file is a matter of zeroing a whole entry. Each file is one sector long. Its location in the disk is derived from its position in the directory. The 1st file is located at track 1, side 0, sector 1. The 2nd file is located at track 2, side 0, sector 1. The 32nd file is located at track 32, side 0, sector 1. Starting bootOS: Just make sure to write it at the boot sector of a floppy disk. It can work with any floppy disk size (360K, 720K, 1.2MB and 1.44MB) and it will waste the disk space as only uses the first two sectors of the disk and then the first sector of each following track. For emulation make sure to deposit it at the start of a .img file of 360K, 720K or 1440K. (at least VirtualBox detects the type of disk by the length of the image file) For Mac OS X and Linux you can create a 360K image in this way: dd if=/dev/zero of=oszero.img count=719 bs=512 cat os.img oszero.img >osbase.img Replace 719 with 1439 for 720K, or 2879 for 1.44M. Tested with VirtualBox for Mac OS X running Windows XP running it, it also works with qemu: qemu-system-x86_64 -fda os.img Running bootOS: The first time you should enter the 'format' command, so it initializes the directory. It also copies itself again to the boot sector, this is useful to init new disks. bootOS commands: ver Shows the version (none at the moment) dir Shows the directory's content. del filename Deletes the "filename" file. format As explained before. enter Allows to enter up to 512 hexadecimal bytes to create another file. Notice the line size is 128 characters so you must break the input into chunks of 4, 8 or 16 bytes. It also allows to copy the last executed program just press Enter when the 'h' prompt appears and type the new name. For example: (Character + is Enter key) $enter+ hbb 17 7c 8a 07 84 c0 74 0c 53 b4 0e bb 0f 00 cd+ h10 5b 43 eb ee cd 20 48 65 6c 6c 6f 2c 20 77 6f+ h72 6c 64 0d 0a 00+ h+ *hello+ $dir+ hello $hello+ Hello, world $ bootOS programs: (Oh yes! we have software support) fbird https://github.com/nanochess/fbird Pillman https://github.com/nanochess/pillman invaders https://github.com/nanochess/invaders bootBASIC https://github.com/nanochess/bootBASIC You can copy the machine code directly using the 'enter' command, or you can create a file with signature bytes with the same command and later copy the binary into the .img file using the signature bytes as a clue to locate the right position in the image file. Or you can find a pre-designed disk image along this Git with the name osall.img Enjoy it! Special thanks to Jakub Kądziołka (NieDzejkob) for finding some bugs and suggesting enhancements. >> ATTENTION << Would you like to learn 8086/8088 programming? Then you must get my new book Programming Boot Sector Games including a 8086/8088 crash course! Now available from Lulu: Soft-cover http://www.lulu.com/shop/oscar-toledo-gutierrez/programming-boot-sector-games/paperback/product-24188564.html Hard-cover http://www.lulu.com/shop/oscar-toledo-gutierrez/programming-boot-sector-games/hardcover/product-24188530.html These are some of the example programs documented profusely in the book: * Guess the number. * Tic-Tac-Toe game. * Text graphics. * Mandelbrot set. * F-Bird game. * Invaders game. * Pillman game. * Toledo Atomchess. * bootBASIC language.