C rand() Function: Random Number Generation

Random number generation in the C language is implemented using pseudo-random number algorithms. Pseudo-random number algorithms are deterministic algorithms that generate a series of seemingly random numerical sequences based on an initial seed value.

In C language, the function for generating random numbers is rand(), which generates a pseudo-random number based on the current seed value and updates the seed value to the next value. The range of values generated by the rand() function is between 0 and RAND_MAX, which is a macro definition representing the maximum value for generating random numbers.

The rand() function operates using the algorithm based on the linear congruential generator. It calculates the next random number using a linear equation, with the specific formula being:

The next value is equal to the product of the previous value and a plus c, all divided by m.

Among them, previous is the current seed value, next is the generated random number, and a, c, and m are fixed constants. The selection of these constants is very important for the quality and distribution of the generated random number sequence.

In a program, it is usually necessary to set a seed value first by using the srand() function to pass a specific value as the seed value to the rand() function. If the seed value is not set manually, the rand() function will use a default seed value. To obtain a higher quality of random number series, you can use the current time as the seed value, for example:

Generate a random seed based on the current time.

This ensures that each time the program is run, the seed value will be different, thereby generating a different sequence of random numbers.