Input and Output Devices

Input and output devices allow the computer system to interact with the outside world by moving data into and out of the system. An input device is used to bring data into the system. Some input devices are:

• Keyboard
• Mouse
• Microphone
• Bar code reader
• Graphics tablet

An output device is used to send data out of the system. Some output devices are:

• Monitor
• Printer
• Speaker

Input/output devices are usually called I/O devices. They are directly connected to an electronic module inside the systems unit called a device controller. For example, the speakers of a multimedia computer system are directly connected to a device controller called an audio card (such as a Soundblaster), which in turn is connected to the rest of the system.

Sometimes secondary memory devices like the hard disk are called I/O devices (because they move data in and out of main memory.) What counts as an I/O device depends on context. To a user, an I/O device is something outside of the system box. To a programmer, everything outside of the processor and main memory looks like an I/O devices. To an engineer working on the design of a processor, everything outside of the processor is an I/O device.

A computer that is dedicated to running a program that controls another device is an embedded system. An embedded system is usually embedded inside the device it controls. Usually they run just one program that is permanently kept in a special kind of main memory called ROM (for Read Only Memory). More processor chips are sold per year for embedded systems than for all other purposes.