The component that points out the address of the instruction to be executed by the CPU next time is the "program counter". In order to ensure that the program can be executed continuously, the processor must have some means to determine the address of the next instruction; and the program counter plays this role. After each instruction is fetched, the program counter points to the next instruction in the sequence.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
What is the component that indicates the address of the instruction to be executed by the CPU next time?
The component that points out the address of the instruction to be executed by the CPU next time is the "program counter".
In order to ensure that the program (understood as a process in the operating system) can be executed continuously, the processor must have some means to determine the address of the next instruction. The program counter plays this role, so it is often called the instruction counter.
Before the program starts executing, its starting address, that is, the memory unit address where the first instruction of the program is located, must be sent to the program counter. Therefore, the content of the program counter is an instruction fetched from the memory. the address of.
When an instruction is executed, the processor will automatically modify the contents of the PC, that is, each time an instruction is executed, the PC will increase by an amount. This amount is equal to the number of bytes contained in the instruction, so that it will always be executed. The address of the next instruction.
Since most instructions are executed in sequence, the modification process is usually simply adding 1 to the PC.
However, when encountering a transfer instruction such as a JMP (jump, full name in foreign language: JUMP) instruction, the address of the subsequent instruction (that is, the content of the PC) must be obtained from the address field in the instruction register. In this case, the next instruction fetched from memory will be specified by a branch instruction, rather than fetched sequentially as usual. Therefore, the structure of the program counter should be a structure with two functions: registering information and counting.
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