Recreating strlen and strcmp in Assembly: A Step-by-Step Guide

Writing low-level functions in assembly might seem daunting, but it’s an excellent way to deepen your understanding of how things work under the hood. In this blog, we’ll recreate two popular C standard library functions, strlen and strcmp, in assembly language and learn how to call them from a C program.

This guide is beginner-friendly, so don’t worry if you’re new to assembly programming. Let’s dive in! ?

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Table of Contents

1. Introduction to Assembly and C Integration
2. What Are strlen and strcmp?
3. Setting Up Your Environment
4. Writing strlen in Assembly
5. Writing strcmp in Assembly
6. Integrating Assembly with C
7. Compiling and Running the Program
8. Expected Output
9. Conclusion
10. Connect on Twitter

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1. Introduction to Assembly and C Integration

Assembly language operates at a very low level, close to machine code. When combined with a high-level language like C, you get the best of both worlds:

• High-level readability.
• Low-level control and optimization.

In this guide, we’ll write two functions in assembly—my_strlen and my_strcmp—and call them from C to demonstrate this integration.

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2. What Are strlen and strcmp?

• strlen: This function calculates the length of a null-terminated string (a string that ends with

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