Posted by Adam Moss on 1999-08-12
> Date: Tue, 10 Aug 1999 18:37:46 -0700 (PDT) > From: Casey Deis <shrap69@xxxxx.xxx> > Subject: boot disk > > > I had a thought cross my mind the other day. > (scary) How do you make a boot disk? > > For example, say I don't have a hard drive or > operating system and say > I have a program on a floppy disk that I want to > run. How do I get my > system to boot from the floppy drive and run the > program? > Shrapnel Shrapnel, When you run a program, you are requesting that the computer toss an executable file's contents into memory, process a file header, and set the CS register and IP register to the first byte of the file. Any programs running in the background (like an operating system) have their address pushed onto the stack segment. So, if you want to run a program which is stored as an executable file, you need an operating system. Don't forget, that IBM's used to run on CPM, and CPM programs were NOT executable under DOS. When you boot up your computer, execution automatically begin as a given point. I think that CS = 0x0000 and IP = 0xFFFF, but I'm not sure. At this point, there's usually a memory check, an option to enter setup, your computer looks for an operating system,first on a floppy drive, then the hard drive, assuming that your computer is setup with default parameters. When hard drives were uncommon, some IBM's ran DOS off of a floppy drive. You inserted DOS when the computer booted, and usually after any program executed, depending on your memory resources. Apple II's did not always use an operating system, and had an understood executable file format. However, PC's have always been Frankenstein's monsters. They were designed to be extremely open-ended, both hardware and software wise. When the original 0x8086 machines came out, there were three operating systems available. If you're a badass, you can write enough assembly language routines to handle executable programs. Don't forget, however that DOS compromises far more than the Command Prompt. All throughout the program, OS calls are made to allocate memory, process input and output, and maintain a file tree. There are very, very few programs that use no OS routines, and you would have to work very, very hard to get even these programs to run. So, if you don't want an OS on your hard drive, simply insert a DOS disk everytime you boot up your computer and exit the installation routine. How do you make a boot disk? Format a floppy disk. Use the /s argument with the format command if you're doing it from the command prompt, or select the appropriate checkbox from the windows prompt. A boot disk is either a sub-set of an operating system or a set of default setting in which to run an installed operating system with. Does that answer your question? Adam Moss _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com
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