NASM

Comprehensive study of nasm covering fundamental concepts and advanced applications.

Introduction to NASM and Assembly LanguageNASM Syntax and StructureRegisters and Memory in x86
Procedures and Modular ProgrammingSystem Calls and Interfacing with Operating SystemsAdvanced Control Flow: Loops, Jumps, and Logic
Building a Simple CalculatorInterfacing NASM with C ProgramsDebugging and Optimizing NASM Code
Breaking Down Complex ProblemsMemorizing Common Instructions and Patterns
Introduction to NASM...NASM Syntax and Stru...Registers and Memory...Procedures and Modul...System Calls and Int...Advanced Control Flo...Building a Simple Ca...Interfacing NASM wit...Debugging and Optimi...Breaking Down Comple...Memorizing Common In...
Advanced Topics

System Calls and Interfacing with Operating Systems

What Are System Calls?

System calls are special requests your program makes to the operating system (OS) to do things like print text, read files, or exit.

Using System Calls in NASM

On Linux, you:

  • Set up arguments in registers (like eax, ebx, ecx)
  • Use the int 0x80 instruction to ask the OS to help

Example: Printing to the Screen

mov eax, 4          ; syscall number for write
mov ebx, 1          ; file descriptor 1 = stdout
mov ecx, message    ; pointer to your message
mov edx, 13         ; message length
int 0x80            ; make the call

Why This Matters

System calls connect your NASM programs to the real world: files, screens, keyboards, and more!

Learning to use them is essential for any non-trivial app.

Examples

  • Writing text to the terminal using a Linux system call.

  • Exiting a program cleanly with a system call.

In a Nutshell

System calls enable NASM programs to interact with the operating system.

Next
Advanced Control Flow: Loops, Jumps, and Logic