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In computer programming, a static variable is a variable that has been allocated "statically", meaning that its lifetime (or "extent") is the entire run of the program. This is in contrast to shorter-lived automatic variables, whose storage is stack allocated and deallocated on the call stack; and in contrast to dynamically allocated objects, whose storage is allocated and deallocated in heap ...
Programmers may further choose to explicitly use the stack to store local data of variable length. If a region of memory lies on the thread's stack, that memory is said to have been allocated on the stack, i.e. stack-based memory allocation (SBMA). This is contrasted with a heap-based memory allocation (HBMA).
The C programming language manages memory statically, automatically, or dynamically.Static-duration variables are allocated in main memory, usually along with the executable code of the program, and persist for the lifetime of the program; automatic-duration variables are allocated on the stack and come and go as functions are called and return.
This shows the typical layout of a simple computer's program memory with the text, various data, and stack and heap sections. The data segment contains initialized static variables, i.e. global variables and local static variables which have a defined value and can be modified. Examples in C include:
This shows the typical layout of a simple computer's program memory with the text, various data, and stack and heap sections. Historically, BSS (from Block Started by Symbol) is a pseudo-operation in UA-SAP (United Aircraft Symbolic Assembly Program), the assembler developed in the mid-1950s for the IBM 704 by Roy Nutt, Walter Ramshaw, and others at United Aircraft Corporation.
A region, also called a zone, arena, area, or memory context, is a collection of allocated objects that can be efficiently reallocated or deallocated all at once. Memory allocators using region-based managements are often called area allocators , and when they work by only "bumping" a single pointer, as bump allocators .
(In fact, the memory is statically allocated at link time.) Every global variable in C code is a static variable in this sense. In C and related languages, "static variable" can also mean a variable defined with the static keyword. For variables declared or defined inside functions, using static makes them static in the general sense.
In computer programming, thread-local storage (TLS) is a memory management method that uses static or global memory local to a thread. The concept allows storage of data that appears to be global in a system with separate threads. Many systems impose restrictions on the size of the thread-local memory block, in fact often rather tight limits.