FLAGS register

The FLAGS <a href="/facts/Processor_register/32RvbUdz">register</a> is the <a href="/facts/Status_register/7KMY9LR9">status register</a> that contains the current state of an x86 <a href="/facts/CPU/Jxp1bqMV">CPU</a>. The size and meanings of the flag bits are architecture dependent. It usually reflects the result of arithmetic operations as well as information about restrictions placed on the CPU operation at the current time. Some of those restrictions may include preventing some interrupts from triggering, prohibition of execution of a class of "privileged" instructions. Additional status flags may bypass memory mapping and define what action the CPU should take on arithmetic overflow.
The carry, parity, auxiliary carry (or <a href="/facts/Half-carry_flag/M2gxsbg9">half carry</a>), zero and sign flags are included in many architectures (many modern (RISC) architectures do not have flags, such as carry, and even if they do use flags, then half carry is rare, since BCD math no longer common, and it even has limited support on <a href="/facts/Long_mode/ITshSuE6">long mode</a> on <a href="/facts/X86-64/cyWvUFlP">x86-64</a>).
In the <a href="/facts/I286/rucEU93g">i286</a> architecture, the register is <a href="/facts/16-bit/bTGS44Ne">16 bits</a> wide. Its successors, the EFLAGS and RFLAGS registers (in modern <a href="/facts/X86-64/cyWvUFlP">x86-64</a>), are <a href="/facts/32-bit/TDMVce8s">32 bits</a> and <a href="/facts/64-bit/AgvkQHkM">64 bits</a> wide, respectively. The wider registers retain compatibility with their smaller predecessors.

FLAGS register open-in-new

FLAGS register