x86 Assembly System Monitor

A small system monitor written in x86-64 assembly for Linux.
It shows basic CPU and memory usage by reading system data directly.

What it does

• Shows total, free, and used memory
• Shows CPU usage percentage
• Reads data from /proc and system calls
• No libraries, just pure assembly

Requirements

• Linux (64-bit)
• NASM
• ld (linker)

Install NASM:

# Ubuntu / Debian
sudo apt install nasm

# Arch
sudo pacman -S nasm

# Fedora
sudo dnf install nasm

Build

nasm -f elf64 monitor.asm -o monitor.o
ld -o monitor monitor.o
chmod +x monitor

Or in one line:

nasm -f elf64 monitor.asm -o monitor.o && ld -o monitor monitor.o

Run

./monitor

Example output:

Memory:
Total: 16384000 KB
Free: 8192000 KB
Used: 8192000 KB

CPU:
Usage: 35%

How it works (simple)

• Memory → uses sysinfo syscall
• CPU → reads /proc/stat
• Calculates usage from active vs idle time

Notes

• Runs once and exits (not live updating)
• Linux only
• Very small and fast

If you want to improve it

• Add a loop for live monitoring
• Add colors or better formatting
• Show more stats (disk, network, etc.)

Why this exists

Just a simple project to understand:

• assembly basics
• Linux syscalls
• how the system actually works under the hood