Program status word

In computers, the program status word (PSW) is an area of memory or a hardware register which contains information about program state used by the operating system and the underlying hardware. It will normally include a pointer (address) to the next instruction to be executed. The program status word typically contains an error status field and condition codes such as the interrupt enable/disable bit and a supervisor / user mode bit.

The program status word (PSW) is 32 bits in length and contains the information required for proper program execution. The PSW includes the instruction address, condition code, and other fields. In general, the PSW is used to control instruction sequencing and to hold and indicate the status of the system in relation to the program currently being executed. The active or controlling PSW is called the current PSW. By storing the current PSW during an interruption, the status of the CPU can be preserved for subsequent inspection. By loading a new PSW or part of a PSW, the state of the CPU can be initialized or changed.

"See also": Status register – a strictly hardware-based type of PSW