Computer systems consist of hardware system. Computer hardware is usually divided into three main part or the three main subsystems: CPU, the memory subsystem, and the input, output subsystem.CPU performs many operations and control computer. The memory subsystem is used to store is being implemented CPU program, with the program data. Output, input subsystem allows CPU and such as a personal computer keyboard and monitor that output and the access device interaction. Computer these components are connected to the bus.A computer to perform a large amount of data processing operations is called the central processor, and is called ( be referrde to as ) CPU. in the computer, it is often called the microprocessor. CPU consists of three main parts: controller, ALU and register group.Memory is also considered ( be knwn as ) memory and memory. It refers to the circuit in the computer, the circuit is maintained either (whatever ) program or data, CPU is immediately available.Input, output subsystem includes input, output device and interface. There are a variety of input, output devices, such as a mouse, printer, sensor, magnetic disk. Input, output interface provides a in internal memory and external input, method of information transmission between the output device. In order to with the CPU interface connected to the communication, computer peripheral equipment requires a dedicated connection. The purpose is to solve the communication connection between central computer and each external equipment difference.