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The instruction counter is at the lower left. The program counter ( PC ), [ 1 ] commonly called the instruction pointer ( IP ) in Intel x86 and Itanium microprocessors , and sometimes called the instruction address register ( IAR ), [ 2 ] [ 1 ] the instruction counter , [ 3 ] or just part of the instruction sequencer, [ 4 ] is a processor ...
A status register, flag register, or condition code register (CCR) is a collection of status flag bits for a processor.Examples of such registers include FLAGS register in the x86 architecture, flags in the program status word (PSW) register in the IBM System/360 architecture through z/Architecture, and the application program status register (APSR) in the ARM Cortex-A architecture.
The Intel 8253 PIT was the original timing device used on IBM PC compatibles.It used a 1.193182 MHz clock signal (one third of the color burst frequency used by NTSC, one twelfth of the system clock crystal oscillator, [1] therefore one quarter of the 4.77 MHz CPU clock) and contains three timers.
The program status word [a] (PSW) is a register that performs the function of a status register and program counter, and sometimes more. The term is also applied to a copy of the PSW in storage. The term is also applied to a copy of the PSW in storage.
A state diagram for a door that can only be opened and closed. A state diagram is used in computer science and related fields to describe the behavior of systems. State diagrams require that the system is composed of a finite number of states. Sometimes, this is indeed the case, while at other times this is a reasonable abstraction.
The program counter (PC) is a special register that holds the memory address of the next instruction to be executed. During the fetch stage, the address stored in the PC is copied into the memory address register (MAR) and then the PC is incremented in order to "point" to the memory address of the next instruction to be executed.
r15 is the program counter, and not usable as a general purpose register; r13 is the stack pointer; r8–r13 can be switched out for others (banked) on a processor mode switch. Older versions had 26-bit addressing, [35] and used upper bits of the program counter (r15) for status flags, making that register 32-bit. ARM 32-bit (Thumb) 8: 16
Since the operating system has effectively suspended the execution of one process, it can then switch context by choosing a process from the ready queue and restoring its PCB. In doing so, the program counter from the PCB is loaded, and thus execution can continue in the chosen process.