# Load task register

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{{Short description|Instruction for x86 processors}}
{{More citations needed|date=December 2009}}
The '''LTR''' [x86](/source/x86) instruction stands for '''load task register''' and is used in [operating systems](/source/operating_systems) that support [multitasking](/source/Computer_multitasking).  LTR is supported only in [protected mode](/source/protected_mode) and [long mode](/source/long_mode), not in [real mode](/source/real_mode) or [virtual 8086 mode](/source/virtual_8086_mode).  It must be executed when the [Current Privilege Level (CPL)](/source/Current_privilege_level) is 0,<ref name=":0" /> and therefore cannot be used by application programs.  LTR loads the special x86 task register with a [segment selector](/source/segment_selector) that points to a [task state segment (TSS)](/source/task_state_segment).  After executing the LTR instruction, the TSS pointed to by the argument is marked busy, but no hardware task switch occurs.<ref name=":0">{{Cite web |title=LTR — Load Task Register |url=https://www.felixcloutier.com/x86/ltr |access-date=2022-12-07 |website=www.felixcloutier.com}}</ref>

The opposite of the LTR instruction is the [STR](/source/store_task_register) instruction, which means store task register and copies the value of the task register to the specified location.  Note that the x86 task register is only accessible directly through the LTR and STR instructions.<ref>{{Cite web |title=STR — Store Task Register |url=https://www.felixcloutier.com/x86/str.html |access-date=2022-12-07 |website=www.felixcloutier.com}}</ref>

==References==
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Category:X86 instructions

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Adapted from the Wikipedia article [Load task register](https://en.wikipedia.org/wiki/Load_task_register) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Load_task_register?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.