int num = (rand() % (upper - lower + 1)) + lower;

The code snippet you provided is written in the C programming language and performs the following steps:

  1. rand(): This is a function in C that generates a random number. It is part of the C standard library and returns a pseudo-random integer between 0 and RAND_MAX.

  2. % (upper - lower + 1): The modulus operator % is used to calculate the remainder of a division operation. In this case, it is used to restrict the range of the random number generated by rand() to the interval between lower and upper, inclusive. The upper and lower are variables that represent the upper and lower bounds of the desired range.

  3. + lower: After getting the random number within the desired range, the lower value is added to it. This ensures that the final result is shifted to be within the specified range.

  4. int num =: The result of the previous calculations is assigned to the variable num, which is of type int. This allows the generated random number within the specified range to be stored and used for further computations or operations in the program.

In summary, the code generates a random number within a specified range (lower to upper) and assigns it to the variable num. The rand() function is used to generate the random number, and the modulus operator % along with addition is used to limit the range of the number.