Input and output — Computing, 11–13 years
How a computer receives information and gives a result back. Computing, 11–13 years.
A conversation with a machine
A computer does not simply work on its own: it receives inputs and produces outputs. A key press, a microphone recording or a touch is input; a picture on the screen, a sound or a printed answer is output. Many programs are a loop of receiving, processing and responding.
The problem it solves
A machine can calculate quickly, but it cannot guess what a person wants or how to show the result. Designers therefore separate the outside world from the program: inputs bring useful information in, and outputs make the answer understandable. This idea made machines useful for communication, not just calculation.
A temperature converter
Suppose a program changes Celsius into Fahrenheit. First, the user inputs 20 °C. Next, the program multiplies 20 by 9/5, giving 36, and adds 32, giving 68. Finally, the screen outputs “20 °C = 68 °F”. The buttons and typed number are inputs; the displayed sentence is output.
The screen is not the whole program
It is easy to call everything you can see “the computer”, because the screen is the part we notice. But a program may receive sound, movement or a hidden sensor reading without showing it immediately. It may also produce an output through vibration or a motor, so ask what went in and what came out.
Interfaces everywhere
When you scan a ticket, the scanner reads a code and the gate gives a light or sound. A fitness watch takes movement as input and outputs steps or a warning. Thinking in inputs and outputs helps you understand why a device reacts, and helps you choose the right sensor or control when making one.
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