--- In [email protected], Muhammad Yasir <[EMAIL PROTECTED]> wrote: > > Dear Nico Heinze, > > Actually i am making a DOS like OS i have created my boot > loader,and now i want that if there is any exe file in my > directory or floppydrive then i must be able to run it. > but problem is that for any kind of executable to be > executed i need interrupts.So now i want to make my own > interrupts not all but some specific and want to load it > IVT. > Please also mention the method that how can i load it in IVT. > Thanks in Advance <snip>
When the CPU boots, it always works in the so-called Real Mode. A modern OS will switch to protected mode (or V86 mode) as soon as possible, but that's a different story. What sort of EXE files do you intend to work with? If it's the NE or PE format as used by Windows since 3.1, no chance. If it's the old MS-DOS format, you will have to populate the IVT on your own. In real mode this is easy to do. I suggest you look at OpenDOS; as far as I recall it (I haven't taken a look in ages) the sources are / were available, and of course this system booted in real mode as well, so you can directly apply what you find there to your own system. Despite that you might want to take a look at those kernel routines of some Linux distribution which are executed when the CPU starts up; you should find some information about what you need there. In general I wonder why you intend to write your own MS-DOS clone, but that's a different story. I simply don't see too much reason to work with a MS-DOS like OS these days, I am admittedly curious about it. If possible, try to get hold of an "ancient" book about MS-DOS PCs written by Peter Norton (yes, that's the founder of the system utility company Norton Enterprises). I don't recall the title, but it gave quite a good introduction into many aspects of this area. Regards, Nico
