The register that tracks the subsequent address of instructions in the CPU is: the program counter. The program counter is where the address of the unit where the next instruction is located is stored.
The program counter is a register in a computer's processor that contains the address (location) of the instruction currently being executed. As each instruction is fetched, the program counter's memory address is incremented by one. After each instruction is fetched, the program counter points to the next instruction in the sequence. When the computer is restarted or reset, the program counter usually returns to zero.
One of the main contents of von Neumann's computer architecture is "program pre-storage and automatic computer execution"! The programs (instruction sequences) to be executed by the processor are pre-stored in the computer's memory in the form of binary code sequences. The processor fetches these codes into the processor one by one and then decodes and executes them to complete the execution of the entire program. In order to ensure that the program can continue to execute, the CPU must have some means to determine the address of the next fetch instruction. The program counter (PC) plays this role, so it is often called the ‘instruction counter’.
Before the program starts executing, the starting address of the program instruction sequence, that is, the memory unit address where the first instruction of the program is located, is sent to the PC. The CPU reads the first instruction from the memory according to the instructions of the PC. (finger). When executing an instruction, the CPU automatically modifies the contents of the PC. That is, each time an instruction is executed, the PC increases by an amount. This amount is equal to the number of bytes contained in the instruction (the number of instruction bytes), so that the PC always points to the next instruction to be fetched. instruction address. Since most instructions are executed sequentially, the process of modifying the PC is usually simply to add the "number of instruction bytes" to the PC.
When the program is transferred, the final result of the execution of the transfer instruction is to change the value of PC, and this PC value is the target address of the transfer. The processor always fetches, decodes, and executes instructions according to the PC pointer, thus realizing program transfer.
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