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ASM in C

Started by MattCarpenter Jul 22, 2002 at 3:00 PM 9 replies 450+ views

Original Post

Jul 22, 2002 at 3:00 PM

I have a problem using djgpp with the asm command. Here is my code: asm("mov %ah, 0"); asm("mov %al, 19"); asm("int 16"); when it goes to the int 16 function though, when i compile it it gives me an error that says "error: operands given don't match any known 386 instruction" although int 16 is suppose to be the correct command. Whats up here? /\/\att [edited by - mattcarpenter on July 22, 2002 4:00:52 PM]

Xanth

Jul 22, 2002 at 4:18 PM

Maybe try...

asm("mov %ah, $0x0");
asm("mov %al, $0x19");
asm("int 16");

I''m not really familiar with the GCC Assembly syntax, I''ve only peaked at it.

"I thought Genius lived in bottles..." - Patrick Star

LessBread

558

LessBread

Jul 22, 2002 at 4:22 PM

Here''s a pretty good reference for AT&T assembly and djgpp: Brennan''s Guide to Inline Assembly

Kars

Jul 23, 2002 at 11:07 AM

is it asm("int 16"); (dec 16) or should it be asm("int 16h"); (hex 16)?

Kars

MENTAL

Jul 23, 2002 at 11:15 AM

it should either be asm("int 0x16"); or asm("int 16h"); - not sure which one djgcc uses (MSVC is 0x16)

Null and Void

163

Null and Void

Jul 23, 2002 at 1:34 PM

Not to say this will actually work, but it will compile:


asm("mov $0, %ah\n"
    "mov $19, %al\n"
    "int $16\n");

In AT&T syntax the value of 'mov' goes on the left, and all constant values are in decimal and prefixed with a dollar sign.

[edited by - Null and Void on July 23, 2002 2:37:14 PM]

MattCarpenter

Author

MattCarpenter

Jul 24, 2002 at 10:05 PM

tanx, damn these mosquito bites ITCH! i just went camping for 3 days in the middle of the desert. Wenatchee Confluence State Park in Washington, actually.