Function

Function returning value

• If we want to use our function in an expression then such function must return a value by using return statement
Syntax
return value ;
• The return statement returns value at the point from where function is called.

returntype FunctionName(datatype args1,datatype args2,...)
{
    Statements 
    ---------------
    return value ;
}

  #include⁢stdio.h>
  int  volume(int l,int b,int h)
  {
    int v;
    v=l*b*h;
    return v;
  }
  main()
  {
    printf("volume is %d",volume(5,2,3));
  }

Volume is 30
  

  #include⁢stdio.h>
  float interest(int p,float r,int n)
  {
    float si;
    si=p*r*n/100;
    return si;
  }
  main()
  {
    printf("Simple interest %f",interest(2500,12.25,3));
  }

Simple Interest is 918.750000
  

  #include⁢stdio.h>
  float circumference(int r)
  {
    float c;
    c=2*3.14*r;
    return c;
  }
  main()
  {
    printf("circumference is %f\n",circumference(2));
  }

Circumference is 12.560000
  

  #include⁢stdio.h>
  int sum(int n)
  {
    int i,s=0;
    for(i=1;i<=n;i++)
        s=s+i;
    return s;
  }
  main()
  {
    printf("sum is %d\n",sum(2));
  }

Sum is 3
  

  #include⁢stdio.h>
  int  max(int a,int b)
  {
    if(a>b)
        return a;
    else
        return b;
  }
  main()
  {
    int z;
    z=max(4117,33451);
    printf("Greatest no. is %d",z);
  }

Greatest no. is 33451
  

Function declaration/prototype

• Function declaration is used to provide information about function in advance to compiler.
• If a function is call before its definition then such function has to be declared before function call.
Syntax
returntype FunctionName(data type of args...);
• In function declaration argument names are optional.
• This declaration can be defined in global as well as local declaration.

  #include<stdio.h>
  float interest(int ,float ,int);
  main()
  {
    float z;
    z=interest(5000,10.25,3);
    printf("Simple intrest is %f",z);
  }
  float interest(int p,float r,int n)
  {
    float si;
    si = p * r * n / 100;
    return si;
  }

Simple intrest is 1537.500000
  

Mathematical functions [ math.h ]

• double sqrt(double x)
• returns the square root of x.
• For ex : z=sqrt(10); =>3.162278
• double pow(double x, double y)
• returns x raised to the power of y .
• For ex : z=pow( 3 , 4 ); =>81
• double ceil(double x)
• returns the smallest integer value greater than or equal to x.
• For ex: z=ceil( 3.1212 ); => 4
• double floor(double x)
• returns the largest integer value less than or equal to x.
• For ex: z= floor( 3.998899 ); =>3
• double round (double x)
• returns the nearest integer value of x.
• For ex: z= round( 3.998899 ); =>4
• For ex: z= round( 3.128899 ); =>3
• double cos(double x)
• returns the cosine of a radian angle x.
• Same syntax can be used for other trigonometric functions like sin, tan etc.