Originally Posted by Papabravo

A dual 4-bit binary counter.

Dual means that there are two(2) binary counters each of which is four bits long.

4-bits means that each of the two counters has 4 binary digits or bits. Each bit can take only the values zero(0) or one(1)

binary means the the counters inputs and outputs are represented in the binary or base two number system.

The 4-bit binary counter has the following set of outputs:

{0000,0001,0010,0011,0100,0101,0110,0111,1000,1001 ,1010,1011,1100,1101,1110,1111}

Each time there is a clock pulse the counter goes to the next state. Some counters go through the sequence in the forward direction and they are called up counters. Some counters go through the sequence in the backward direction and they are called down counters. Some counters can do both depending on the state of a control input.

What are they used for? Everything. IMHO it is a dead heat between counters and shift registers for the title of most useful part.