A large C program is divided into basic building blocks called C Function. C function contains set of instructions enclosed by "{ }" which performs specific operation in a C program. Actually, collection of these functions creates a C program.

C functions are basic building blocks in a program.

• A large program in c can be divided to many subprogram
• The subprogram posses a self contain components and have well defined purpose
• The subprogram is called as a function
• Basically a job of function is to do something
• C program contain at least one function which is main()

Types of C functions

1. User defined function: main()
2. Library Function: printf(), scanf(), sqrt() etc.