Imperative programming: Difference between revisions

Revision as of 01:10, 14 June 2022

Revision as of 01:16, 14 June 2022

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[[File:Computer-memory-map.png|thumb|right|Computer memory map]]

''C'' allows the programmer to control which region of memory data is to be stored. ''Global variables'' and ''static variables'' require the fewest [[Clock signal|clock cycles]] to store. The [[call stack|stack]] is automatically used for the standard variable [[Declaration (computer programming)|declarations]]. ''[[Manual memory management|Heap'']] memory is returned to a [[Pointer (computer programming)|pointer variable]] from the [[C dynamic memory allocation|<code>malloc()</code>]] function.

* The ''global and static data'' region is located just above the ''program'' region. (The program region is technically called the ''text'' region. It's where machine instructions are stored.)

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:* ''Local variables'' declared using the <code>static</code> prefix are also stored in the ''global and static data'' region.<ref name="geeksforgeeks"/> Unlike global variables, static variables are only visible within the function or block. Static variables always retain their value. An example usage would be the function <code>int increment_counter(){ static int counter = 0; counter++; return counter;}</code>

* The ''[[call stack|stack]]'' region is a contiguous block of memory located near the top memory address.<ref name="lpi-ch6-p121">{{cite book

|title=The Linux Programming Interface

|last=Kerrisk

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|page=122}}</ref> are called ''automatic variables''<ref name="cpl-ch1-p31"/> and are stored in the stack.<ref name="geeksforgeeks"/> They are visible inside the function or block and lose their scope upon exiting the function or block.

* The ''[[Manual memory management|heap'']] region is located below the stack.<ref name="geeksforgeeks"/> It is populated from the bottom to the top. The [[operating system]] manages the heap using a ''heap pointer'' and a list of allocated memory blocks.<ref name="cpl-ch1-p185">{{cite book

|title=The C Programming Language Second Edition

|last1=Kernighan