Introduction to x86 Assembly (DOS)

My first tutorial ever on programming with much more to follow. This set of assembly language videos will provide what you need when we start to discuss about computer viruses and beyond.

[СветославАнгелов-эб]

And here am I...in 2024. Returning to the roots.

[HellJustFroze]

and that was the moment I realized I was subscribed to you.

[CrayTheZ]

“Or something like that..” I love this guy already! Lmao

[freecrac]

Now i like to show how to redirect some assembler mnemonics and debug commands for to telecontrol debug within a batchfile and some pipe(> <) operators. Description: The first step is to redirect all commands into a temporary textfile and the second step is to redirect the temporary textfile to debug.

These following examples have to be copy and paste into a new texttfiles. And the textfile have to be renamed with the "bat" file-extension: Example: "Hello.bat"

@echo off
echo a cs:100>tmp.deb
echo mov dx, 108>>tmp.deb
echo mov ah, 9>>tmp.deb
echo int 21>>tmp.deb
echo ret>>tmp.deb
echo db "Hello World!$">>tmp.deb
echo g=cs:100 107>>tmp.deb
echo q>>tmp.deb
debug<tmp.deb>tmp.inf
del tmp.deb
type tmp.inf

Variation and alternative example with a similar content:

@echo off
echo e cs:100>tmp.deb
echo ba 08 01 b4 09 cd 21 c3>>tmp.deb
echo a cs:108>>tmp.deb
echo db "Hello World!$">>tmp.deb
echo g=cs:100 107>>tmp.deb
echo q>>tmp.deb
debug<tmp.deb>tmp.inf
del tmp.deb
type tmp.inf

[rafaeloledo]

9:25, i think u meant the first 8 bits or one byte of the AX

[schweizerd]

Why is the instruction different for letter 'H' DEC AX but for 'e', 'l', 'l', 'o' DB 65 6C 6C 6F? DOS looks similar to whats done in linux but you do interrupt 0x80, mov edx, length / mov ecx, message / mov ebx, 1 (standard output) / mov eax, 4 (sys_write) - tells it to print to screen on interrupt, setting eax to 1 and recalling int80 will exit the program

[lukesymmons]

danooct1 favourited this video so it must be good

[CZghost]

RIP headphone users. Dude your voice is so clipping that my ear hurts. I know that I'm a little bit late and I guess many people have pointed that out long before me (frankly, I didn't seek it out), but I hope that if they did, you learned about that and talk to the mic from further distance...

[nikolaikalashnikov]

I always thought DOS had null terminating Strings ? You said 0D 0A is a newline. And you also said that 24 is the dollar sign ($). But I'm sure the dollar sign ($) is printable too.
Which would mean that the end of the series of printable characters woud be 24 00, right ?

[Ikkepop]

why does everyone pronounce DIR as DURRR just sounds so derpy...

[jacqueslavoie]

Do you mean treating a data 'type' like it's part of the code, maybe. Not sure but that's the way I'm seeing it. Good vid. I'm a little late but hey.

[michaelperugini]

so how do you take a ASM instruction set and actually create a executable/com file that will run from DOS? I have a 1987 code that i want to make into a program how do you do that thru debug?