Whether the operands are 8-bit or 16-bit is specified in the
opcode of the instruction by the word bit (bit 0), also
whether REG field in the modR/M specifies the destination
operand is determined...

Here's what some of the values mean in the modR/M byte:
Operands Mod Reg R/M Displacement
Reg,Reg 11 XXX XXX Here R/M is treated as Reg ...

On the MS-DOS system functions for input I usually
use, atimes a Carriage-Return character is at the
end of the buffer lest the maximum count of
characters is met. 21/3F
0xd ends the input, that...

[[[AxxAxLLlaLLLaXBxG]]]]

mov cx, 0x10
mov ax, 0x123
db 0x66
shl ax, cl ; shift 0x123 into high-word of EAX
db 0x66
shr ax, cl ; shift back into low-word of EAX, that is, AX

You would need...

mov ds, seg buff ; works in MASM
mov si, offset buff

All you need is the segment address on which the buff string
lies, this is because your generating an .EXE.

Here's one way to wait for a...

To print out your commandline arguments with
function 9, simply add a '$' to the end of the actual command tail.
example:

xor bx, bx
mov bl, [0x80]
mov byte [bx+0x81],'$'
mov bx, 0x81

But...

16-bit OS dos I need help vortex reign....
Hello, to answer your question NASM16 is a 16-bit (80x86) assembler
for MS-DOS.
To access commandline parameters, they are passed by the
loader (your...

Color text-mode memory lies at segment 0xb800 and is 4000 bytes
in length 80*25*2 cuz each visible character on the screen
is accompanied by a text attribute byte.
00000000 Text Attribute Byte...

Access violation is caused when a program attempts to
access memory reserved for the operating system.
I thought this could only happen in a windows program?

I assume your using MASM:

mov ax,...

Why do you open the file with 3Dh when you already
have the file handle returned by 3Ch?
This will create two file handles that refer to the same
file, so if you want to be a well-behaved...

INT 21 - DOS 2+ - "LSEEK" - SET CURRENT FILE POSITION
AH=42h
AL=origin of move
00h - start of file
01h - current file position
02h - end of file
BX=file handle
CX : DX = (signed) offset from...

I do not know if the above is right....

I would assume the .386 directive means to generate
32-bit code. And your calling 16-bit Dos interrupts???
I don't know what else is wrong, I do not use MASM.

It's been a while, but I think this is right.
Upon execution of the bootloader
CS,DS,ES will be zero,
And there is a 512-byte stack allocated by the BIOS.
SS (points where?) SP ?
I do not know...

I added this to quickly boot your code with Bochs:

times 1474560 - ($ - $$) db 0

The code worked.
Your problem most likely is how you wrote it out to the disk.
The 512-byte image has to be...

The high-byte and low-byte of AX,BX,CX,DX are also
referable by name.
AX-AH|AL
BX-BH|BL
CX-CH|CL
DX-DH|DL
So to refer to the lower eight bits of AX the name
AL is used.

For example:

AX and BX are 16-bit registers.

His origin is at 7C00h because the BIOS bootstrap
will load the first sector of a drive containing a valid boot sector
at physical address 07C00h and will jump to it
loading CS with 0 and IP with...

All values stored in memory are represented in binary,
so I would assume that if you had a decimal value
it would be the ASCII representation of a decimal value,
as if it were entered in by the...

I assume you would like to turn the value in memory
into the asci representation of the decimal value.
For example, the value 20h (32d) in a byte
into the asci characters 33h '3' and 32h '2',...

And also do not forget that the quotient cannot be larger
than the destination register.
So when using a 16-bit divisor make sure the quotient
will not be larger than 16-bits, the size of AX.
And...

With a 32-bit divisor it is divided against the quad-word
in EDX:EAX, quotient is returned in EAX, remainder in EDX.
You said you do not understand the hi and lo part,
they represent the high and...