Introduction - If you have any usage issues, please Google them yourself
A relatively independent program module that has a specific function that can be invoked by another program, called function in the C language. The main purpose of introducing a function is to solve two problems, one is to solve the duplication of code. If a program section needs to appear multiple times in the program, every time to write out the troublesome and makes the program at this time the share variable length segment is defined as a function. Call directly where it is required. Two is the need of structured modular programming.