在采用段式内存管理的架构中，代码段（code segment / text segment）通常是指用来存放进程执行代码的一块内存区域。这部分区域的大小在进程运行前就已经确定，并且内存区域通常属于只读, 某些架构也允许代码段为可写，即允许进程自修改(en:self-modifying code)。 在代码段中，也有可能包含一些只读的常数变量，例如字符串常量等。

操作系统在装载一个进程时会进行进程地址空间的分段，而代码段通常处于最底部，即最低地址部分，而堆和栈在高处，所以在允许代码段可写的架构上，当堆或栈内存溢出时，代码段中的数据就会开始被覆盖。

In computing, a code segment, also known as a text segment or simply as text, is a portion of an object file or the corresponding section of the program's virtual address space that contains executable instructions. The term "segment" comes from the memory segment, which is a historical approach to memory management now known as paging. When a program is stored in an object file, the code segment is a part of this file; when the loader places a program into memory so that it may be executed, various memory regions are allocated (in particular, as pages), corresponding to both the segments in the object files and to segments only needed at run time. For example, the code segment of an object file is loaded into a corresponding code segment in memory.