computing Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and softw ...

, a code segment, also known as a text segment or simply as text, is a portion of an

object file An object file is a file that contains machine code or bytecode, as well as other data and metadata, generated by a compiler or assembler from source code during the compilation or assembly process. The machine code that is generated is kno ...

or the corresponding section of the program's

virtual address space In computing, a virtual address space (VAS) or address space is the set of ranges of virtual addresses that an operating system makes available to a process. The range of virtual addresses usually starts at a low address and can extend to the h ...

that contains

executable In computer science, executable code, an executable file, or an executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instruction (computer science), in ...

instructions.

Segment

The term "segment" comes from the memory segment, which is a historical approach to

memory management Memory management (also dynamic memory management, dynamic storage allocation, or dynamic memory allocation) is a form of Resource management (computing), resource management applied to computer memory. The essential requirement of memory manag ...

that has been succeeded by

paging In computer operating systems, memory paging is a memory management scheme that allows the physical Computer memory, memory used by a program to be non-contiguous. This also helps avoid the problem of memory fragmentation and requiring compact ...

. 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 Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembe ...

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. The code segment in memory is typically read-only and has a fixed size, so on

embedded system An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is e ...

s it can usually be placed in

read-only memory Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing sof ...

(ROM), without the need for loading. If the code segment is not read-only, then the particular

architecture Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and construction, constructi ...

allows

self-modifying code In computer science, self-modifying code (SMC or SMoC) is source code, code that alters its own instruction (computer science), instructions while it is execution (computing), executing – usually to reduce the instruction path length and imp ...

. Fixed-position or position-independent code may be shared in memory by several processes in segmented or paged memory systems. As a memory region, the code segment may be placed below the heap or stack in order to prevent heap and

stack overflow In software, a stack overflow occurs if the call stack pointer exceeds the stack bound. The call stack may consist of a limited amount of address space, often determined at the start of the program. The size of the call stack depends on many fa ...

s from overwriting it.

References

{{Reflist Executable file formats Memory management

Segment

See also

References