Self contained program segments designed to perform a specific, well-defined task.

All C programs have one or more functions. The main() function is required in every C program and it is from within it that all other functions are called. The purpose of most functions is to process information passed to it by the part of the program that called it, though some functions take no parameters at all.

Functions in C are conceptually like an algebraic function from math class.


If you pass a value of 7 to the function: f(7), the value 7 gets "copied" into x and used everywhere that x exists within the function definition: f(7) = 72 + 4*7 + 3 = 80.

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