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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 register that indicates where a computer is in its program sequence.
Instruction Pointer (IP): Holds the offset address of the next instruction to be executed within the code segment (CS). It points to the first byte of the next instruction. While the IP register cannot be accessed directly by programmers, its value changes through control flow instructions such as jumps, calls, and interrupts, which alter the ...
In the x86 assembly language, the JMP instruction performs an unconditional jump. Such an instruction transfers the flow of execution by changing the program counter.There are a number of different opcodes that perform a jump; depending on whether the processor is in real mode or protected mode, and an override instruction is used, the instructions may take 16-bit, 32-bit, or segment:offset ...
Movement instructions take (register, memory) operands: MOVE 1,2 is register-register, and MOVE 1,1000 is memory-to-register. PDP-11: 7: 6 (if FPP present) R7 is the program counter. Any register can be a stack pointer but R6 is used for hardware interrupts and traps. VAX [32] 16: The general purpose registers are used for floating-point values ...
Below is the full 8086/8088 instruction set of Intel (81 instructions total). [2] These instructions are also available in 32-bit mode, in which they operate on 32-bit registers (eax, ebx, etc.) and values instead of their 16-bit (ax, bx, etc.) counterparts.
An autorelative pointer is a pointer whose value is interpreted as an offset from the address of the pointer itself; thus, if a data structure has an autorelative pointer member that points to some portion of the data structure itself, then the data structure may be relocated in memory without having to update the value of the auto relative ...
CPUs that do not use sequential execution with a program counter are extremely rare. In some CPUs, each instruction always specifies the address of next instruction. Such CPUs have an instruction pointer that holds that specified address; it is not a program counter because there is no provision for incrementing it.
In computing, the instruction register (IR) or current instruction register (CIR) is the part of a CPU's control unit that holds the instruction currently being executed or decoded. [1] In simple processors, each instruction to be executed is loaded into the instruction register, which holds it while it is decoded, prepared and ultimately ...