The five classic components of a computer are briefly described below. Each component is discussed in more detail in its own section. The operation of the processor is best understood in terms of these components.

The datapath manipulates the data coming through the processor. It also provides a small amount of temporary data storage.

The datapath consists of the following components.

Control generates control signals that direct the operation of memory and the datapath. The control signals do the following.

Memory holds instructions and most of the data for currently executing programs.

The rest of the data is held in programmable registers, which can only hold a limited amount of data.

Input is data coming into the processor from external input devices such as keyboards, mice, disks, and networks.

In modern processors, this data is placed in memory before entering the processor. Input handling is largely under the control of operating system software.

Output is data going from the processor to external output devices such as displays, printers, disks, and networks.

In modern processors, this data is placed in memory before leaving the processor. Output handling is largely under the control of operating system software.

The processor executes a sequence of instructions that are located in memory. Execution of each instruction involves at least the first three of the following activities. The last four activities are required for some, but not all, instructions.

The program counter (PC) hold the address of the next instruction. For a simple processor, the arithmetic-logic unit (ALU) performs all arithmetic and logical operations.

The activities are approximately in time order. However, some of the activities can be overlapped in time.

The organization of the data path can be determined from these activities. Where an activity requires selecting among different options depending on the instruction, there will be a multiplexer that selects the appropriate option as directed by a control signal.