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Combinational Logic

# Binary Encoder

A **binary encoder** is a unit which changes discrete inputs into binary coded
combinations of outputs. One place where encoders are frequently used is in the input
units of computers. In most computers, it is not practicable to enter numbers
and other information into the computer in binary form, as this would require
the programmer to spend too much time in the detailed effort of accurately
representing large numbers or complicated alphabets and symbols.
Thus the computers are generally equipped with encoders, units which change
discrete inputs into a combination of binary coded outputs.

The example illustrated below is a simple encoder which accepts as inputs ten
discrete signals (I_{0} ... I_{9})
representing the decimal digits 0 ... 9. It is presumed that
only one of these signals is HIGH (logic 1) at any given time. On its output
it produces the proper combination of pulses to represent the input signal
in straight binary-coded decimal notation.

The simple encoder can generate an incorrect output when more than a single
input is HIGH. A **priority encoder** is used in such cases.