main.c(16): warning C275: expression with possibly no effect

This warning indicates that there may be an expression in your code that does not have any effect on the program's execution. This means that the expression is evaluated, but the result is not used in any way.

For example, consider the following code:

int x = 5;
x + 2;

In this case, the expression "x + 2" is evaluated, but the result is not used. This means that the expression has no effect on the program's execution, and the warning will be triggered.

To fix this warning, you should either remove the expression if it is not needed, or assign the result to a variable or use it in some other way if it is necessary for your program's logic.