Execute in place

In <a href="/facts/Computer_science/lN3pEyPz">computer science</a>, execute in place (XIP) is a method of executing programs directly from long-term storage rather than copying it into <a href="/facts/Random-access_memory/DuD4bxh6">RAM</a>. It is an extension of using <a href="/facts/Shared_memory/zmpH7WuV">shared memory</a> to reduce the total amount of memory required.
Its general effect is that the program text consumes no writable memory, saving it for dynamic data, and that all instances of the program are run from a single copy.
For this to work, several criteria have to be met:

<ul><li>The storage must provide a similar interface to the <a href="/facts/Central_processing_unit/Jxp1bqMV">CPU</a> as regular memory (or an adaptive layer must be present).</li>
<li>This interface must provide sufficiently fast read operations with a <a href="/facts/Random_access/1cxrCk3r">random access</a> pattern.</li>
<li>The <a href="/facts/File_system/FdPm90uc">file system</a>, if one is used, needs to expose appropriate mapping functions.</li>
<li>The program must either be <a href="/facts/Linker_(computing)/pn1hztYe">linked</a> to be aware of the address the storage appears at in the system or be <a href="/facts/Position-independent_code/jhgplpJ0">position-independent</a>.</li>
<li>The program must not modify data within the loaded image.</li></ul>
The storage requirements are usually met by using <a href="/facts/Flash_memory/Cn8JsStx">NOR flash memory</a> or <a href="/facts/EEPROM/0yAMFY0I">EEPROM</a>, which can be byte-addressed for read operations, although it is a bit slower than normal system RAM in most setups.

Execute in place open-in-new

Execute in place