How to Calculate time taken by execution of functions in C?

There are some specific Debug tools available online for this.....I would suggest trying them, there are also specific ways to work out what will take the most time. The other thing to look at is the parts of your program the system is spending the most time on (usually most programs spend about 90% of thier time processing about 10% of the code as there are usually functions that are used a lot more or which are naturally going to take a lot longer). and try to optimise these parts of the program.