gcd is the greatest common divisor (GCD) function, usually used to find the greatest common divisor of two or more integers.

The greatest common divisor, also known as the greatest common factor and the greatest common factor, refers to the largest divisor of two or more integers. The greatest common divisor of a and b is recorded as (a, b). Common methods for finding the greatest common divisor include: prime factorization method, short division method, euclidean division method, and phase replacement and subtraction method.

The syntax format of the GCD function is: GCD(number1,number2, ...), where Number1, number2, ... are 1 to 255 values. If the parameter is a non-integer, it will be truncated. Round up.

It should be noted that if the parameter is non-numeric, the function GCD returns the error value #VALUE!. If the argument is less than zero, function GCD returns the #NUM! error value.

When editing the function, you need to pay attention to two special cases. One is that 1 can be divided by any number, and the other is that only itself and 1 can be used as divisors to divide the prime number.

How to find the greatest common factor in C language:

1. Exhaustive method (enumeration method): the simplest and most intuitive method.

The specific steps are: first find the minimum value min of the two numbers (the greatest common divisor must be less than or equal to the minimum value of the two numbers), and then decrease from the minimum value min (the loop end condition is i > 0). If you encounter a number that is a factor of both integers, use break to exit the loop. The value i obtained at this time is the greatest common divisor of the two positive integers.

2. Subtraction method: Nicomanches method, which is characterized by doing a series of subtractions to find the greatest common divisor.

3. Euclidean division method: also known as Euclidean algorithm, it refers to the calculation of the greatest common divisor of two non-negative integers a and b. Application areas include mathematics and computers. The calculation formula is GCD(a,b) = GCD(b,a mod b).

Specific steps: First find the remainder of the two numbers num1 and num2. Then assign num2 to num1, and let the divisor num2 of the last remainder be used as the dividend of the next remainder. At the same time, the current remainder is used as the divisor for the next remainder. In this way, we keep dividing until the remainder is 0. At this time, the divisor num2 is the required greatest common factor.