Object code

Note: there is technically a difference between “object code” and “machine code”, but in this document, we’ll treat them as the same thing for simplicity.
Object code is the output of a compiler before linking, while machine code is the final executable code.
Also, “object code” is sometimes executed by the operating system and not directly by the hardware, but again, we’ll ignore that distinction here.

What is object code?

Object code is essentially the compiled version of a program, translated into a low-level language that the computer’s CPU can understand and execute directly.

This low-level language is often referred to as machine code or machine language.

When you write a program in a high-level programming language (like C, C++, or Rust), you typically write it in a way that’s easy for humans to read and understand. However, computers can’t directly execute this high-level code - as there’s no way that the CPU could be expected to understand every programming language in this list.

To make the program executable, we need to convert it into a form that the CPU can understand. We do this using a compiler, which translates the high-level code into object code (machine code).

Summary

• Source code is the human-readable code that we write.
• A compiler translates source code into object code (machine code).
• Object code is the low-level code that the CPU can execute directly.

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