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Front panel of an IBM 701 computer introduced in 1952. Lights in the middle display the contents of various registers. 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 ...
This pointer function method can result in saving one machine instruction, and avoids the indirect jump (to one of the branch instructions). The resulting list of pointers to functions is almost identical to direct threaded code, and is conceptually similar to a control table. The actual method used to implement a branch table is usually based on:
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 ...
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 ...
Drop the stack pointer to the current base pointer, so room reserved in the prologue for local variables is freed. Pops the base pointer off the stack, so it is restored to its value before the prologue. Returns to the calling function, by popping the previous frame's program counter off the stack and jumping to it.
In computer programming, assembly language (alternatively assembler language [1] or symbolic machine code), [2] [3] [4] often referred to simply as assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence between the instructions in the language and the architecture's machine code instructions. [5]
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The RETURN instruction pops the return address from the stack into the instruction pointer and execution resumes at that address. (Examples: x86 , PDP-11 ) In architectures such as the Motorola 96000 , the stack area may be allocated in a separate address space, which is called 'Stack Memory Space', [ 22 ] distinct from the main memory address ...