Intro to x86 Assembly Language (Part 1)

[@bonbonpony]

08:34 Actually, MUL and DIV also affect EDX. The MUL instruction stores the higher half of the result in EDX, while DIV stores the remainder from division there. If one dosn't know about that, one can be very surprised that suddenly their EDX is getting clobbered with "random" numbers after division/multiplication.

[@OmbreeTV]

Omg thank you so much, i've been trying to understand a code for a couple of days and couldn't figure out why edx was being pushed and pop before and after a multiplication

[@小鳥ちゃん]

*boops*

[@mikicerise6250]

OMG, thanks soo much. If not for your comment I would still be mystified at the bizarre results of my test code. xD "Multiplication never works... division only works sometimes... duuhhh..." xD

[@mikicerise6250]

Another thing I've discovered on the MacOSX x64 side of things (still using NASM) is if you divide 64 bit integers the quotient is apparently given by RAX:RDX, for reasons I still don't understand, so since both RAX and RDX are 64 bit integers, aside from giving you the wrong answer, if anything substantial is in RDX it's a ticket to overflow-land unless you initialize RDX at 0 first.

[@Kokurorokuko]

How is storing higher half of the result useful?

[@kraio-sfu]

“Assembly language is basically just a human-readable form of machine code” As a complete beginner who has just looked at Assembly code for the first time, I am crying both tears of laughter and pain at this statement

[@mansodev]

@Kraio have you tried lua or python? Their more higher level and easy to learn.

[@nickstill2666]

I hope you didnt give up but you'll want to start somewhere besides x86 assembly. There are loads of languages that make more sense and are more natural to write for a beginner.

[@kraio-sfu]

nick still Which one would you suggest? I have recently started wanting to make my own computer on a breadboard, but I want to be able to actually make programs for it. Do you think the Motorola 68010 would be an okay pick?

[@kraio-sfu]

The Planebagel Oh I absolutely love Python, it’s my main programming language. I just find it funny because calling Assembly “human-readable” is a very generous statement

[@nickstill2666]

@@kraio-sfu hell ya! A big project but could be rewarding. My personal preference (arm chair opinion) would be to start with a 6502. The Assembly lang is straight forward and there is a community around ROM creation for the 6502 with python and you can even by a kit for breadboarding it

[@c0n-5truct-0r6]

I just had hours over hours of Assembly lessons at University... 6 Videos and I finaly get how it works! Well done! Thanks a lot!

[@serdart7220]

Thanks for this great, very comprehensible, video. Organization of the video (introduction and then development of the body part of this training) really is very nice, 👌👍

[@sgyniguez]

Didn't make sense to me the first time I watched it. After reading through parts of a book, following a tutorial on tutorialspoint, this made SO much more sense. Thank you my man.

[@omarelric]

Salvador Yniguez hey dude, what book was it?

[@mrkewi1]

@@omarelric The Art Of Assembly

[@omarelric]

Fazil Sultan hey, I somehow came across the same book anyways 😂

[@omarelric]

Samyakt Jain “the art of assembly”

[@samyaktjain698]

@@omarelric I am beginner , please help me , where I learn Reverse engineering ?

[@memy4460]

Absolutely brilliant. Nothing, I mean nothing at all worked on my computer from this tutorial.

[@robert-jh3rr]

should be Intel cpu ...if u have amd won't work

[@ivandres73]

Excelent, straight to the point and no "suscribe bull".... Great presentation and introduction

[@ivandres73]

@reena mola because you reference processors registries (eax, ebx, etc) without brackets ([ ]). You use brackets when referencing memory address ([0x400008]).

[@ivandres73]

@reena mola "mov eax,[ebx]". imagine ebx=0x40000. So we are saying: "mov eax, [0x40000]". imagine memory at 0x40000 = 20. So we are saying: "move eax, 20". Note, syntax might change a bit of how to reference a registry depending on the tool (at&t, intel, oracle...). But that is not the case for the example above.

[@ivandres73]

@reena mola No, registries do not have addresses, they are just... "there". Memory has addresses, and the more memory you have (2GB, 4GB, 8GB, etc) the more "addresses" you have.

[@ivandres73]

​@reena mola no. you are talking about the "sections" that a registry has. Every 32bit x86 registry has 4 sections, and those are different from memory addresses. memory addresses refers to the RAM. registries do not have addresses. registries can store addresses. references to sections of a registry is with 'ax, al, ah', and other special words; not with brackets. any RAM address is refered with brackets[ ]. [eax+4] = go to the RAM, at the location of eax+4. eax+4 = add 4 to the value stored in eax. (not sure if this is even permitted)

[@ivandres73]

@reena mola Make good use of knowledge! 🤙🏽

[@chevalier5691]

This video is not really an "intro" but fortunately it's exactly what I need.

[@blackham7]

Eurgh You're such a squidward

[@marcussmithwick6326]

Finally a good tutorial on x86

[@asheralbrecht2554]

You are the only person that i could find online that can explain things extremely well! Thanks so much!

[@FoxhoundULM]

Hey Davy, what a masterpiece of a tutorial series, I wanted to have an idea of what Assembly programming looked like and better understand very low level programming, well man i wasn't expecting to find such a brillant tutorial in video ! Thanks, and if you want to carry on with more advance stuffs in assembly, please don't hold your breath !

[@xrafter]

Assembly is a processor language but in human format.

[@PAUNOMOLUSCO]

I gave my thumb’s up to every episode of this series.

[@ahmedomar222]

Thanks for making this video series for free. I am really glad. It is a massive help to me. Plus you really simplify it which good for a beginner like me.

[@vojtechstoklasa3417]

I am programmer for quite some time, but your videos seem to be the right way for me to move into asssembly more! Cheers

[@meno437]

Crack your own programs good way of learning

[@alexcocinda384]

Thank you so much man, this really helped me to get the basics of this thing. I may be able to pass my college exam now.

[@Learnerofthings]

I know this is 3 years old, but this is a very good series and should be continued :)

[@CircularLogic54]

I love your enthusiasm at the end

[@DavyBot]

Example code: github.com/code-tutorials/assembly-intro Slides: docs.google.com/presentation/d/19nVBqrXdsvRHhAXPDwQodSoux-b_PXF9dBe-bfZJS2M

[@godwhomismike]

I really hope you teach computer science courses at your local college(s).

[@Darkleaf-Music]

godwhomismike From what I understand, computer science is more about mathematics and high level abstraction stuff. Most of the courses I've seen teach with Java, though I did know of least one school which focused on embedded systems.

[@godwhomismike]

I've had plenty of CS instructors that were not that great with math, but could code extremely well.

[@bradley1995]

@10:37 Wow amazing descriptions on the code. Seeing it in such fashion helped me understand the translation between that and c code. I believe there will be great insight learned from your video's! Thank you friend

[@myles9193]

Been trying to teach myself x86 for a while, definitely not the 'nicest' language but a great feeling when it works

[@drozcan]

reverse engineering feels like pro

[@wooseliedestine9382]

@@drozcan Yes indeed

[@bradley1995]

I'm learning to create a simple "compiler" using java for a lex/parser and to generate asm code. I'm super excited!

[@suntexi]

I feel privileged that the first language I learnt was IBM 1401 autocoder. I then went onto IBM 360 Assembler and so the concepts of x86 Assemble language are relatively easy. 360 processors had 16 general purpose registers and 4 (I think) floating point registers. Addresses of storage were calculated as base and displacement, that is, four bits denoting the base register and twelve bit denoting the offset from the address in that register.

[@g4yktzgjx6]

First part was informative but. You left out what the different keywords means once you get to 10:08. msg db "Hello World!",10,0 //Here we append ' '(newline) and the numeral 0 to our string in order to 0 terminate it(0-terminated string) - which is good practice. Also you didn't create a string of bytes but an array of bytes. You defined bytes(db). So you defined an array containing characters "Hello world! ". Which you could also have done like so although very messy: msg db 'H', 'e' , 'l',' l', 'o', ' ', 'w', 'o', 'r', 'l', 'd', '!', 0x0a len equ $ - msg // equ is used to define contants. "$" evaluates to the assembly position at the beginning of the line containing the expression(current address). Also maybe tell us why it works. It is not obvious for everyone that you're taking the address exactly after making your string and subtracting the address of the very start of the string. Please remember to tell us what each keyword does and means.

[@DavyBot]

You don't need to end your string with a 0x00 unless you're dealing with C library functions. The system call for writing to stdout requires the length and that 0x00 doesn't matter. Also... What do you think the difference between a string and an array of character bytes is? :) Also, to each their own. I write the bytes out in hex format as 0x0a instead of just 10 or even 0xa because I'm used to working with hex editors (as people working with low level languages like this tend to be). But, yes, I could have explained in more detail that the $ was for taking the location after the string.

[@g4yktzgjx6]

There is no difference between a string and an array of characters. But in the video you called it a string of bytes. Which I find wrong. It is an array of bytes or a sequence of bytes representing a string.

[@DavyBot]

They're all valid terms. You probably hear people use "string of bytes" more when they've had to deal with unicode strings in addition to ascii strings. But you're just being picky (or not being picky enough?), it isn't "wrong". en.wikipedia.org/wiki/String_(computer_science)#Representations www.google.com/search?tbm=bks&q=%22string+of+bytes%22

[@homelessrobot]

A more relevant section of that wikipedia article is probably: en.wikipedia.org/wiki/String_(computer_science)#Non-text_strings (maybe it wasn't there two years ago) The meaning of the word 'string' has evolved to mean 'a sequence of character elements' (or whatever) over time, but its really just another word for vector, array, or sequence. In particular if you are working on x86 in machine instructions, you should probably already be somewhat familiar with this because there are a whole class of string operations for x86 that aren't related t zero terminated character encoding anything. They are just for operating over a contiguous, addressable sequences of elements of a given size.

[@beasusan521]

happy I've found your videos. from this video alone, I already understood more, then in my lecture to this topic. Thanks for uploading such a great video series and taking your time explaining it so good!

[@043_fazlerabbi5]

He is best

[@hjrgf]

​​​@@043_fazlerabbi5 yeah the video is formatted to make it easy to learn all of the assembly stuff I remembered much more stuff than other tutorials 10/10 tutorial

[@kingbeencent]

This video suddenly appeared on my playlist after watching virus testing videos, I am interested in remember the Assembly Language, thanks for this content!!!!!

[@tardis2005]

Though these have been here a bit, I've just recently found them. Well explained, Davy. Should keep me busy for a while. I've always liked the closest to the metal. Thought C was as far as I could go with any proficiency, but maybe not. It is good practice for VIM.

[@J0rD5t3R]

This video just saved my whole day. Thank you! Now on to the rest of the playlist...

[@myartchannel8205]

Hurray! Now we're getting somewhere, assembly is a set of different languages. I'm definitely bookmarking this.

[@a.v7998]

This was really very intresting! I think learning assembly teaches you a lot about computers!

[@regretkagami1004]

I'm so glad you've made these videos. I been using asmtutor which is good, but it goes down a lot easier when you've got a good video series to follow along to. Dope shit man, thank you

[@Rogue_Art]

One thing you should mention is that there are two ways to write x86-64 assembly. The one you've shown in your video is the Intel syntax which is a lot nicer and readable, but is read right-to-left. The other one, which is just as common, is the AT&T and GNU syntax which is more complex and is read left-to-right.

[@tree9380]

I came here from michael reeves saying this is a easy language and my friend says its not, naturally im going to torture myself to spite my friend. This will be my first coding language, wish me luck

[@undefinedchannel9916]

cmon atleast learn a high-level language to get used to big brain code logic like loops and if statements and stuff like that

[@tree9380]

@@undefinedchannel9916 my suffering is and will be immeasureable till im done and move on to less suffering like c++

[@tree9380]

@steev i do hate myself imdeed

[@wassuupman764]

@@tree9380 start with python or JS dude... you will lose motivation

[@xrafter]

Do c first it will help you understanding the assembly and amd64 abi . Abi is just a way of two programs to talk to each other in assembly .

[@shvideo1]

Thank you for this great tutorial. Covered a lot of information and produced a working executable. You are a great teacher!

[@10hourslooney25]

Thank you. And no needless Videohive inspired introductions! Straight to the point.

[@gregwoolley]

Nice video! Good pace, well structured and clearly explained, thank you!

[@kr1spybac0n]

Your explained this way better than my professor ever did

[@Vermilicious]

Short and easy-to-follow presentations. Good job.

[@trifalgarh]

I wish we had a professor for assembly & computer architecture like you in my Uni 😅

[@MrGSA1310]

I wish I had a professor who teach me something instead of forcing me to watch this kind of videos in order to have any hope of success for his exam 😢

[@grandmakisses9973]

@@MrGSA1310 that’s what I’m scared for I’m going to university soon :( wish me luck

[@MoveTrueRecords_]

Bro u just explained this easy

[@finlayhutchinson7370]

Very helpful I watched a few tutorials and this is the easiest one to understand thank you.

[@jefferystone1]

Good job - ignore the haters - we all have to start somewhere which is why many are here.

[@maelstrom57]

I hadn't been this excited to print "hello world" before.

[@jpalacios117]

You reeeeaaaly hace to watch it more than once... Great video!

[@gumboe2007]

Great video Davy, clear and easy to follow. Thanks for putting it together

[@crabmothflunderbum7770]

Outstanding video series, thank you so much, it really helped. You are a pioneer of knowledge

[@BytebroUK]

There's probably no-one who cares about this, but. My first ever 'proper' programming gig was in about 1979 and was a "This is stupidly slow. Speed it up, if you can" kinda thing. I turned 4 lines of FORTRAN 'IF' statements into about a page and a half of inline assembler, and instead of taking around 24 hours, it now ran in about 2 hours and produced the same answers. Go me!

[@Videosuser]

You've saved my college semester, sir. Thank you.

[@germondhipolito9883]

03:00 does it mean that The Stack is physically on the CPU, like the registers? It's different from the stack in RAM?

[@HonsHon]

when I first got it to compile, I was so happy haha

[@Fabik11]

That was pretty cool.

[@yelircaasi]

This is great, and very helpful. Thanks for making it.

[@rexseppe7084]

Thanks, finally someone with a good tutorial!

[@booleanscene8882]

The information in this video is spot on

[@Mbro-dq2do]

You can also install NASM natively on ANY Mac via homebrew package manager.$- brew install nasm

[@sameermubeen8495]

very useful and informative video, amazing work

[@wqatch]

2:42 32-bit's max is 4,294,967,296, while 64 bit's max is 18,446,744,073,709,551,616. 64 bit's max is actually 32 bit max' squared.

[@peterparker-fg5kr]

conclusion 64 bit are no more useful than 32 bits

[@wqatch]

@@peterparker-fg5kr *laughs in >4GB of ram*

[@husamalzahrani2503]

Really thanks man we really were need this courses for learninh you really amazing and great persone dont stop 🔥👍👍👍👍🔥🔥

[@dezcraft_dev]

Davy you are a wonderful teacher

[@tomaszx7760]

Nice. Many years ago i write some Asm code in dos. And use int 13h mode to create games.

[@lucasbpsx8566]

Wow, you teach Go and x86, you're a god

[@Bod88]

I really enjoyed this. I'm currently reading the PDF Reverse Engineering For Beginners (understanding Assembly Language) and it gets a bit heavy at times when it talks about different CPU architecture sets and different compiler output. But your video is straight to the point. Thanks

[@sealkeen]

5:44 *accumulator register, the first important one. Something that is missing is the general purpose registers' description/declaration/definition.

[@ArneChristianRosenfeldt]

I wish that new students learn a sane language with Registers R00 .. R31 .

[@MosinShooter109]

Oh man what a find! Knowledgeable and understandable.

[@slowedmood7440]

1 week of college in 10min thank you

[@gustavosalmeron2013]

Everytime I try to learn assembly, I thank Dennis Ritchie for creating C.

[@DividedWarrior]

Very helpful video. You are the best! Very fun language. Wish me luck!

[@pendergastj]

What a great video. Thank you for making this! Subscribed.

[@tracetv8115]

10:32 I am a little bit confused. How does the System know, if we want to store the value 4 into the eax to calculate with it or if we want a system call? I don't get it?

[@infrakazos]

Finally, some good fking -food- _tutorial_

[@trulyspinach]

Thank you for the great video, very clear explanations.

[@PerreRust]

Great video, no bullshit, and excellently explained!

[@N3fario]

Thanks for the tutorial, it's pretty useful. Sometimes there's things that aren't explicitly explained though, which I have to google. For example, knowing what $? in bash is, or what equ/db do es in assembly. Still, nice tutorial

[@elikelik3574]

Thanks a lot for such a great explanation. I have seen a lot of super videos but I'm not clever enough to understand them, but now eventually I start to understand =D . Again Thanks a lot.

[@Dom-zy1qy]

When he says "the syntax can differ between different assemblers" does he mean some will default to using AT&T syntax, others intel syntax? Or is he referring to something else?

[@Daniel-m4l1p]

Awesome content, thanks for sharing this!

[@ahmedghallab5342]

شكرا كان ذالك رائعا Thanks it was amazing

[@awecwec3720]

very clear and efficient thank u

[@satejtawade]

Good video. Thnx sir. Kindly upload more video on assembly language

[@IronJmo]

For anyone else who ran into this issue like I did, mov eax, 4 is for 32 bit. If you're working on a 64 bit like I am the system call number is different. mov eax, 1

[@lilraahdreadlockvideosandm1648]

I’m about to watch this 😁

[@eddiemorales4728]

Have you watched it yet?

[@lilraahdreadlockvideosandm1648]

Eddie Morales yea I watched all 6 videos

[@lilraahdreadlockvideosandm1648]

Eddie Morales your about to watch ?

[@eddiemorales4728]

@@lilraahdreadlockvideosandm1648 nice.. I watched the first and bookmarked and subscribed for later.. I got worried.. you told us you were going to watch a month ago and disappeared 😆

[@kmengkomsot1479]

Thanks for the tutorial🥰🥰🥰

[@EzProgrammingPro]

Subbed, this is useful for reverse engineering and game hacking

[@PureASM-ShellCoder]

Excellent video, thanks man ! 👍👏

[@isme364]

Comments are full of assholes your explanations are great started taking programing seriously recently and i was able to i understand you perfectly thank you

[@Rachaelshaw7]

Oh my gawd i just realised my teacher at school was teaching us assembly language... Holy crap

[@UniqueGlover]

Great video, easy to follow

[@joriskbos1115]

I've seen assembly code that just uses syscall instead of int 0x80 and as far as I know it does exactly the same. Does it matter what I use? My best guess is that syscall might be something specific to nasm and int 0x80 is more common across assemblers.

[@Rokannon]

I am thinking about watching this series. Did anyone watch the whole thing? Is it worth the watch? Thank you.

[@ivancizse]

How to make the following program in 8086. Input: Characters (10 maximum) Output: Simulates the operation of a queue of a maximum of 10 characters allowing the user insert and delete elements, with the permanent display of the queue on the screen (cursor handling).

[@wisdommonger]

I'd love to see the final right half of the video, but it's populated by overlays. I've got annotations turned off, but they still show up.

[@myartchannel8205]

You know, I'm glad I know other languages as well. I might find a way to automate some of this.

[@masqueradethemusketeer3101]

i wanted a basic tutorial...but this guy jumped from basic arithmetic operations to making things that i didn't undertand...

[@techtimefly]

@9:14 what is the value of ecx before adding to ebx?

[@samaellovecraft]

Thanks for the knowledge!

[@toopkarcher]

Very nice video. Hope the flashing isn't a big thing for the rest of the series. #epilepsyWarning 😂

[@willychrosnik1925]

thanks bro. amazing video

[@sivaaj8504]

To the point. Excellent video.

[@johnrothe6981]

Great contents, great communication!

[@srshk257]

Very cool series. I wish my professors taught like you. Any plans on doing a series on ARM64 or x86_64 assembly?

[@ShivanshPlays1]

I think this series is about x86_64

[@flameofthephoenix8395]

Hm, I'm trying to directly alter the bytes of a .exe in order to write a program, hopefully I can skip that whole assembler nonsense and get straight to machine code, however I keep getting an error when I try to run a .exe in administrator mode that the .exe cannot be found it will state the exact file path of the .exe I'm attempting to run, which is odd because I can see very clearly the .exe is located on that branch in file explorer. It may be worth mentioning the way I'm going about all this is creating a .txt file that has nothing in it, changing the extension to .exe manually, then opening the file for Binary as #1 in Excel and putting a bunch of bytes of programming into the .exe file, this seems more likely to work than other methods like inputting the byte information into an ASCII .txt before changing to a .exe due to some ASCII characters potentially getting messed with by the .txt before the transformation to a .exe happens.

[@colza1025]

For those who are curious about the list of available system calls. asm.sourceforge.net/syscall.html