A register that goes through a prescribed sequence of states upon the application of input pulses is called counter. A counter that follows the sequence of states as binary number sequence is called binary counter. An n bit binary Counter consists of n flip flops and can count in binary from 0 to 2^{n}-1 states.

Counters are further classified in 2 categories: Synchronous and Ripple Counters. The main difference between the two is, in synchronous counter all the flip-flops receive same Clock as input where as in ripple counters output of one flip flop is used as a source to trigger the other flip-flops.

Example: Binary Ripple Counter: - It is a counter which follows binary number system for counting and has series connection of flip flops such that output of one serves as input for next higher order flip flop. The flip flop holding least significant bit receives incoming count pulse.

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