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Questions - real-mode

Segmented far pointer allocation in 16bit x86 MS-DOS real mode

I'm trying to get my head around programming real mode MS-DOS in C. Using some old books on game programming as a starting point. The source code in the book is written for Microsoft C, but I'm trying...
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IronPug

c

dos

x86-16

real-mode

watcom

Votes: 0

Answers: 1

Latest Answer

It appears your OpenWatcom C compiler is defaulting to using C89. In C89 variable declarations must be at the beginning of a block scope. In your case all your code and data is at function scope, so t...
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Michael Petch

Base poiner offset in x86 real mode

Having a following code: .code16 _entry: xorw %ax, %ax movw %ax, %ds movw %ax, %ss movw %ax, %es movw $0x7c00, %ax movw %ax, %sp movw %ax, %bp pushw $49 callw ...
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TheCPPNoob

assembly

x86

bootloader

att

real-mode

Votes: 0

Answers: 1

Latest Answer

Answer in a comments. The value is actually stored at 4(%bp), but in this case 6(%bp) just happens to be the same, but in general, 6(%bp) would be undefined (some old stack frames data).
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TheCPPNoob

String Output in Real-Mode by using LODS instruction

I'm need to write function, which output a string in real-mode. There is that code: ;; ds:si - string address, cx - length of string cld putc: lods mov ah, 0x0E xor bh, bh int 0x10 ...
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SubtRose

assembly

x86

real-mode

Votes: 0

Answers: 1

Latest Answer

lods isn't a valid instruction mnemonic; you probably mean lodsb. On my assembler (nasm), a token that isn't a valid mnemonic gets parsed as a label instead, and so no code is emitted. Thus your lods...
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Nate Eldredge

Binding PIT, PIC and IVT together to get a sleep() function

I have decided to write a small program to check, if I am able to implement a sleep function in a real mode app. Thats, what I did: Added an IRQ_0 handler function to the address at 0x0000:0x80, corr...
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adivanced

nasm

intel

x86-16

real-mode

Votes: 0

Answers: 1

Latest Answer

I guess, I figured out, what i was doing wrong. First of all, PIC is already initialized by BIOS, defaulting IRQ0 to interrupt 0x08. Also we need to send the EOI to the PIC in the end of out custom in...
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