Inputoutput device

The computer systems all share a dependence on components that allow the actual interaction between computer and users. These electronic components are categorized under two general headings: input devices and output devices. Input devices transfer information from the designer into the computer's central processing unit (CPU) so that the data, encoded in binary sequencing, may be manipulated and analyzed efficientiy. Output devices do exactiy the opposite. They transfer binary data from the CPU back to the user in a usable (usually visual) format. Both types of devices are required in a CAD system. Without an input device, no information can be transferred to the CPU for processing, and without an output device, any information in the CPU is of litde use to the designer because binary code is lengthy and tedious.

Central Process Unit

The computer's central processing unit (CPU) is the portion of a computer that retrieves and executes instructions. The CPU is essentially the brain of a CAD system. It consists of an arithmetic and logic unit (ALU), a control unit, and various registers. The CPU is often simply referred to as the processor. The ALU performs arithmetic operations, logic operations, and related operations, according to the program instructions.

The control unit controls all CPU operations, including ALU operations, the movement of data within the CPU, and the exchange of data and control signals across external interfaces (system bus). Registers are highspeed internal memory-storage units within the CPU. Some registers are user-visible; that is, available to the programmer via the machine instruction set. Other registers are dedicated strictiy to the CPU for control purposes. An internal clock synchronizes all CPU components. The clock speed (number of clock pulses per second) is measured in megahertz (MHz) or millions of clock pulses per second. The clock speed essentially measures how fast an instruction the CPU processes.

0 0

Post a comment