A code segment is a portion of a computer program that contains executable instructions. It is part of the program's memory layout, which also includes other segments like the data segment and stack segment. The code segment is where the actual code written in programming languages like Python, Java, or C++ resides, allowing the computer to perform specific tasks. In many programming environments, the code segment is read-only to prevent accidental modification during execution. This helps maintain the integrity of the program. When a program runs, the operating system loads the code segment into memory, enabling the processor to execute the instructions sequentially.