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    Monday, November 16, 2020

    Functions - Introduction

    A function is a block of code that performs a specific task. In C, we can divide a large program into the basic building blocks known as function.

    A function can be called multiple times to provide reusability and modularity to the C program.

    Reusability is the main achievement of C functions. By using functions, we can avoid rewriting same logic/code again and again in a program.

    There are two types of functions in C programming:

          Library Functions: are the functions which are declared in the C header files such as scanf(), printf(), gets(), puts(), ceil(), floor() etc.

          User-defined functions: are the functions which are created by the C programmer. It reduces the complexity of a big program and optimizes the code.

    A function will have three aspects

    1. Function Declaration / function prototype

    2. Function Call

    3. Function Definition.

    1. Function Declaration / function prototype:

    A function must be declared in a C program to tell the compiler about the function name, function parameters, and return type.

    A function prototype is simply the declaration of a function that specifies function's name, parameters and return type. It doesn't contain function body.

    Syntax of function prototype

    returnType      functionName(type1 argument1, type2 argument2, ...);

    Ex:

    void     sum(int   x, int   y);

    The function prototype is not needed if the user-defined function is defined before the main() function.

    2. Function call: 

    Function can be called from anywhere in the program. Control of the program is transferred to the user-defined function by calling it.

    Syntax of function call

    functionName(argument1, argument2, ...);

    Ex:

    sum(a,b);

    3. Function definition:

    Function definition contains the block of code to perform a specific task. When a function is called, the control of the program is transferred to the function definition. And, the compiler starts executing the codes inside the body of a function.

    Syntax of function definition

    returnType    functionName(type1 argument1, type2 argument2, ...)

    {

        //body of the function

    }

    Ex:

    void    sum(int x, int  y)

    {

    int  sum=x+y;

    printf(“ sum is;%d”. sum);

    }

    Different aspects of function calling

    There are four different aspects of function calls:

          function without arguments and without return value

    Ex: void sum( );

          function without arguments and with return value

    Ex: int sum( );

          function with arguments and without return value

    void   sum(int a,int b);

          function with arguments and with return value

    int   sum(int a,int  b);

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