Updated: Feb. 6 2026 | Created: Jan. 29 2026
What Is Computer Code?
Computer code is a set of instructions written to tell a computer what to do. These instructions can be created in a form that humans can read, or in a form that computers can directly understand and execute.
In simple terms, computer code is the language used to communicate with computers.
There are several types of computer code, but the most common ones include source code, machine code, bytecode, pseudocode, and markup or styling code.
Source Code
Source code is a human-readable set of instructions written using programming languages such as C, C++, Python, Java, and many others. Developers write source code to create software, applications, and operating systems.
This type of code is easy for humans to read and understand, but it usually needs to be compiled or interpreted before a computer can run it.
Machine Code
Machine code is the lowest-level form of computer code. It consists of raw binary instructions written in 0s and 1s, which are directly executed by the computer’s hardware (CPU).
Unlike source code, machine code is not readable by humans and is specific to a particular processor architecture.
Assembly Code:
Hexadecimal Code:
Binary Code:
Bytecode
Bytecode is an intermediate type of code that sits between source code and machine code. It is designed to be platform-independent, meaning it can run on different operating systems using a virtual machine or interpreter.
A common example of bytecode is Java bytecode, which allows the same program to run on Windows, macOS, or Linux without rewriting the source code.
Source Code (example.java):
Bytecode (example.class):
Pseudocode
Pseudocode is an informal, human-readable way of writing instructions. It is used to outline the logic and steps of a program without following the strict rules of any programming language.
Pseudocode is not meant to be executed by a computer—it is mainly used for planning, teaching, and explaining how an algorithm works.
Markup and Styling Code
Markup and styling code are used to structure and format content rather than perform calculations or logic. These codes define how text, images, and layouts appear on a screen.
Common examples include:
- HTML (HyperText Markup Language) for structure
- CSS (Cascading Style Sheets) for design and layout
- Markdown for simple text formatting
These types of code are widely used in websites and documentation.
HTML or HyperText Markup Language Code:
CSS or Cascading Style Sheet Code:
MD or Markdown Code:
Conclusion
Computer code is the foundation of all modern technology—from simple web pages to complex operating systems. While different types of code serve different purposes, they all work together to turn human ideas into instructions that computers can understand and execute.
Understanding these basic types of computer code is an important step toward learning how software and digital systems really work.