Definition: Digital Electronics
The main objective of any electronic circuit is to transfer and manipulate information. This information is represented as either an electrical voltage or a current, but mostly voltage. In a digital system the value that needs to be sent is represented (encoded) as a series of high and low voltages instead of a continuous range of voltages as is the case in an analogue system.
Such a single high or low voltage (1 or 0) is called a binary digit or bit. Since a bit can only represent 2 values (1 and 0) a number of them has to be used together to represent a value larger than 2 - similar to the case where several decimal digits (0-9) are used together to represent values greater than 9. In most systems 8 bits (1 byte) are sufficient to represent a single analogue value.
For example, if a pressure sensor is measuring a value of 1kPA and it has to encode that value as a electrical signal in a digital system, it would send the following series of bits 0000 0001. For 2kPA it would send 0000 0010, for 3kPA it would be 0000 0011 and so on.
Although digital electronics makes sending information more complex than analogue electronics it is far more immune to noise and information corruption. It is not easy for a low voltage (0) to be inadvertently changed to a high voltage (1) by some noise spike.
Also see: Analogue Electronics