Questions tagged [assembly]

An assembly language is a low-level programming language for a computer, or other programmable device, in which there is a very strong (generally one-to-one) correspondence between the language and the architecture's machine code instructions.

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String helper functions in NASM Win16 Assembly

Environment NASM is required to build this program, and DosBox is required to run it. I'd recommend installing these using the ...
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1answer
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Ubuntu 18.04.3 ASCII strings length with embedded VT100 control codes

As my applications rely on VT-100 emulation, I found that I had to do quite a few workarounds to determine the number of visible characters in a string with embedded VT-100 control codes. So that led ...
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Cat program in x64 FASM

I wrote cat program in x64 FASM and I would like to know if there is anything that can be improved. This implementation of cat supports: Reading from stdin. Multiple arguments. I checked few cases ...
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1answer
78 views

Cat program in x86 NASM

I wrote cat program in x86 NASM and I would like to know if there is anything that can be improved. This implementation of cat ...
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Ubuntu 18.04.3 LTS get terminal columns and rows NASM

As part of the prologue of all my console applications, I need to determine the extents of the current terminal so if there are less than 132 columns or 43 lines the user can be warned output may not ...
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Display hexadecimal value stored at a register

I read a book about OS development and faced with a simple exercise: write a function that prints a hexadecimal value stored at a register. The program runs as a boot sector. I would really ...
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188 views

String routines

These are a few string routines (just the mem* ones). I've tried to optimize them the best I can without having them be too big, but I'm unsure if I've done a good ...
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1answer
92 views

Loading a file from a FAT32 filesystem in 16 bit real mode on x86 (Intel syntax assembly)

I am writing a bootloader that needs to load a file from a FAT32 filesytem. Since I need to load both the root directory first to find the start of the file, and then the actual file, I wrote a ...
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2answers
81 views

Find the maximum number in an array of numbers

The task is to find the maximum number in an array of numbers. I have taken every number in the array to be byte-sized. I have written the code such that the result is stored in ...
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1answer
61 views

Multiplying a Matrix with its Transpose

Currently, I am in the process of optimizing a MIPS assembly program that takes a n x n matrix and multiplies it with its transpose. I am trying to optimize my matrix calculation algorithm so that it ...
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1answer
34 views

Transposing a square matrix (n x n)

I wish to transpose a square matrix, permanently overwriting it. This is not the same as creating a 2nd matrix with the transposed contents of the 1st matrix. I call the procedure with 3 parameters: ...
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1answer
234 views

Brainfreeze: A Brainfuck compiler in C

BrainFreeze This is my implementation of a brainfuck compiler in C. The instruction to build/run the project (GitHub repo) can be found here. I am first converting the brainfuck source to x86 ...
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Decoding assembly instructions in a Game Boy disassembler

I am coding a game boy disassembler in C++. The program (simplified here) converts a vector of byte into an assembly instruction and print it. To do so, it iterates through the vector of bytes (char)...
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79 views

Multi-line text reader (x64 ASM)

Building upon my previous question, I have come up with a method that'll search through a buffer and return a pointer to the end of the line. The primary purpose of the function to extract rows from a ...
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1answer
129 views

Reading all file contents via x64 assembly

I have come up with the following snippet by building upon the answers given to my StackOverflow question. Just trying to get some other eyeballs to review things so that they can point out any ...
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1answer
142 views

Brainfuck to NASM compiler in Haskell

After reading this article on writing a Brainfuck interpreter in Haskell and achieving awful performance with it (for example, mandelbrot generating 37.5 minutes on an old Intel Atom powered laptop) I'...
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3answers
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A simple shellcode that will kill all your processes GNU/Linux x86_64

So I made a simple shellcode that will kill all your process. Now I would like to know, can it be done in some better way? It contains 13 bytes. Thanks for all your feedback Assembly: ...
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783 views

strlen and strcmp implementation in x86 FASM assembly

I wrote my own implementation of strlen and strcmp from C in x86 FASM and I would like to know is there anything that should be changed or improved. strlen needs string in eax and is returning length ...
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Collatz Conjecture Disprover Unit - Googol Edition

The Wikipedia article about the Collatz Conjecture has these quotes: If the conjecture is false, it can only be because there is some starting number which gives rise to a sequence that does not ...
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Find some X^2 - Y^2 equal to a given Z

Request input (Z) from user, \$-65535 \leq Z \leq 65535\$. Check if \$(X^2)-(Y^2)=Z\$ (while \$0 \leq X,Y \leq 1000\$). I wrote a code which will receive Z from user, if it's negative, store the ...
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119 views

Test whether a number is a Harshad Number

A little code I wrote that will check if the entered 4-digit number is Harshad or not (Harshad number is one which divided by the sum of its digits will leave no remainder, special Harshad is the same ...
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1answer
102 views

Expand every bit into a byte

I have the following code: ...
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1answer
55 views

X86 Feature detection in preparation for Long Mode

These are the three steps that need to be taken in order to successfully activate Long Mode. Error reporting is sparse as most real hardware for developing an OS is 64 bit but probably still a good ...
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1answer
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Compare two strings in extended memory - classic 8052

I'm looking for a simpler code that isn't resource hungry that can compare two strings stored in different locations in the extended memory of a classic 8052 (namely the AT89S52 microcontroller) to ...
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Swapping variable length strings asynchronously with connected microcontroller (Byte-banging)

I have an AT89S52 and an AT89C4051 microcontroller (both in the 8052 family) in which the bit lines of the data bus, one control pin and one status pin are connected together. In code, the data bus is ...
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3answers
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Simple puts() function in x64 assembly

I'm trying to write as simple I/O library in x64 using linux syscalls ...
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1answer
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Variadic Functions in NASM Win64 Assembly

Simple variadic function implementation in NASM Assembly. When implemented like I have below: sum.asm ...
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1answer
367 views

Tower of Hanoi in NASM Win64 Assembly

This program is an implementation of the classic puzzle Tower of Hanoi! This is my first mostly recursive Assembly program. Any advice and all topical comments on code optimization and conventions is ...
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x64 Windows Assembly - Structs in Assembly

I'm trying to code a simple person database using structs and arrays in assembly. Each person has a firstName, lastName, ...
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1answer
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Guessing game in NASM Win64 Assembly

Still learning Assembly. This program is a simple guessing game to test most of the new things I've learned! Any advice and all topical comments on code optimization and conventions is appreciated! ...
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Checking if a number is prime in NASM Win64 Assembly

I'm just learning Assembly. This program is a simple attempt to determine if a given number is prime or not. Any advice and all topical comments on code optimization and conventions is appreciated! ...
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1answer
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gcc constant time implemenation [closed]

I need to make the following function time constant - I have already removed if statements and have written it down to one line in the loop. ...
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1answer
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Main loop in assembly for a Brainfuck interpreter

I have written 2 Brainfuck interpreters, one in C++, then another in C++ with Assembly inner loop. My interpreter code can be found here (C++/ASM, requires MSVC and MASM) and here (C++). Both are ...
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1answer
206 views

Hex Dump Utility in x86-64 Assembly: Version 1.1

I recently posted a code review and received some very useful feedback. I have spent some time implementing the suggested improvements/fixes, and wish to post a follow up review, with the new and ...
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347 views

Hex Dump Utility in x86-64 Assembly, under Linux

As a relative newbie to Assembly programming, although I can get my programs to work, I have no idea if they are disastrously constructed or not. I have created a simple Hex Dump Utility, using x86-...
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Disassembler for intel 8080 v2

As many suggestions were given for the code I posted here, I decided to show you the new version for review. I Removed the OpenCatalog class, ...
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Disassembler for intel 8080

I have written a disassembler for Intel 8080, able to translate binaries into opcodes and parameters. Sorry for posting so much code, but everything posted here is useful for the understanding of the ...
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1answer
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string length in x64 assembly (fasm)

Please critique this very, very basic routine which returns the length of a given char buffer or "string." ...
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MIPS Assembly Program to access elements in the 4x4 matrix, row or column-major oder

This MIPS Assembly program will make you access the elements in the 4x4 matrix in either row or column-major order i.e. accessing all elements row by row or column by column. Output is posted below ...
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1answer
79 views

Console TicTacToe implementation

I am new to assembly and I want to know how I can improve this implementation both by speed and/or binary size optimization and making code to read and support easily. Platform: Linux, x64 Assembler:...
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2answers
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Multiplying big numbers using Long Multiplication

Three weeks ago I posted Multiplying big numbers using Karatsuba's method where I made reference to my version of the classical long multiplication. That's what I'm posting today so people can compare ...
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1answer
673 views

Linked List in x86 assembly(MASM)

Module 1: ...
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1answer
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Block Allocation in Fixed-Size Block Allocator

The following routine is the block-allocation procedure in a fixed-size allocator being written for library use. It is designed to be accessed from C++ (the un-mangled symbol name is ...
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1answer
432 views

SIMD memcpy assembler implementation

I am fairly rusty with assembler, let alone the AT&T syntax. I would appreciate it if someone with more experience could please review the following memcpy implementation. Note that this will only ...
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Multiplying big numbers using Karatsuba's method

The Karatsuba algorithm, first published in 1962, aims to speed up the multiplication of big numbers by reducing the number of 'single-digit-multiplications' involved. Because of its complexity (...
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1answer
1k views

Convert unsigned Integer to ASCII in x86 assembly

This is my best effort to code an x86 32 bits to get an unsigned int (4 bytes) and convert it into a string. My strategy was successively divide the number by ten and fulfill the remainder of the <...
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1answer
588 views

Dynamic Fibonacci algorithm in x86 (MASM)

My task was to implement this algorithm that uses memoization to calculate fibonnaci numbers: ...
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1answer
1k views

Quick Sort in x86 assembly (MASM)

My task was to implement Quick Sort in assembly from pseudocode. ...
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Euler's Totient Function in x86 assembly (MASM)

My task was to implement Euler's totient function, and I'm looking for any and all criticism. ...
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Caesar cipher in i686 assembly + MMX

I have written the following implementation of the Caesar cipher for an old Linux computer with a Pentium MMX chip. The code has been written with the following design goals in mind: the code should ...