The greatest common divisor (GCD) is the largest integer that can divide two given integers without a remainder. For example, the GCD of 6 and 8 is 2: 6/2=3 and 8/2=4. Euclid's Algorithm is an efficient way of calculating the GCD of two numbers. The following program uses a while loop to implement Euclid's Algorithm to find the GCD of two numbers a user enters.