char *vidmem=(char *)0xb8000

[slacker]

By "hack", I mean "code which isn't compliant with the ISO C Standard". You're breaking the C Standard by merely writing an operating system

well im hearing two different things.....

[Whatever5k]

The type cast is totally fine, use it. I do not understand the problem you have with it. Tim was referring to your code:

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pointer = 0xb8000;

_This_ is indeed something which is not ISO-C compliant. Use following instead which *is* ISO-C compliant:

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char *pointer = (char *) 0xb8000;

End of story

[nullify]

Assigning an int to a pointer is a hack which will only work on machines with a flat address space, so you need the cast to let you do it.

Tim never said that type casting is against the ISO C standard! The only problem is when you don't explicity tell the compiler what you are intending to do. In other words, there is nothing hackish about doing:

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char *vidmem = (char *)0xb8000;

There's nothing wrong with doing this to reference memory.

[slacker]

aah i see. i thought he meant that type casting was a hack and wasnt compilant with the standard

[slacker]

why is writing an OS breaking the C standard (according to Tim) ?

[Therx]

The C standard includes what should be in the C library etc. Now I'm sure that your OS doesn't have a complete libC which makes it not compliant

[slacker]

thanks to all this posting i finally see what is going on

(char *)0xb8000; <---makes to pointer from an integer

vidmem=(char *)0xb8000 <-----setting the video pointer equal to the pointer which points to the video memory

yes! i should of caught this on the first response but im slow.

[Tim]

why is writing an OS breaking the C standard (according to Tim) ?

Well, on the x86, you've got to use assembly language somewhere. If that's not inline then you're breaking the standard by using the asm extension (which is pretty common).

The ISO C Standard provides for freestanding and hosted implementations of C. A hosted implementation is what you'll use under a full OS, with main, <stdio.h>, and everything else. A freestanding implementation consists of the language itself, a few header files consisting only of #defines (no library functions), and not much else.

By writing an OS you can conform to a freestanding implementation. And by writing an OS, you can provide an environment for other people to write hosted programs.