1. Functions allow programmers to organize code into reusable blocks that perform specific tasks. A function contains a block of code that is executed when the function is called. 2. Functions have a declaration, definition, and call. The declaration specifies the function name and parameters. The definition contains the code that is executed. The call transfers program control to the function. 3. Functions can be categorized based on whether they have parameters and return values. They can also be called by value, where the parameter value is copied, or by reference, where the memory address is used.

1. Programming in C
Module IV
Rajagiri School of Engineering &
Technology

2. • Functions
• Elements of User Defined Function
• Methods of calling a Function
Contents
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3. Functions

4. • You can divide up your code into separate functions. Logically
the division is such that each function performs a specific task.
• A function can also be referred as a method or a sub-routine or
a procedure.
Functions
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A function is a group of statements that together perform a task.

5. 1. Function Prototype (function declaration)
2. Function Definition
3. Function Call
Elements of User Defined Function
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6. • A function declaration tells the compiler about a function
name and how to call the function.
• Syntax:
• Example:
void xyz(int, char,float);
1.
2.
1. Function Declaration
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returntype function_name (Parameter List);

7. • Contains all the statements to be executed.
2.Function Definition
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returntype function_name (parameter list)
{
//body of the function
}

8. Example
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9. • When a program calls a function, the program control
is transferred to the called function.
3. Function Call
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function_name(arguments list);

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11. int max(int num1,int num2);
void main()
{
int a=100,b=200,ret;
ret=max(a,b);
printf(“the max value is %d”,ret);
}
int max(int num1,int num2)
{
int result;
If(num1>num2)
result=num1;
Else result=num2;
return result;
}
Example
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12. Example
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13. 1. Function with no arguments and no return value
2. Function with no arguments and a return value
3. Function with arguments and no return value
4. Function with arguments and a return value
Categories of User-defined Functions
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14. 1. Function with no arguments and no return value
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Function Call

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2. Function with no arguments and a return value

16. 3. Function with argument and no return value
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17. 4. Function with argument and return value
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18. • Call by Value
• Call by Reference
Methods of calling a Function
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19. • In call by value method, the value of the variable is passed to
the function as parameter.
• The value of the actual parameter can not be modified by
formal parameter.
• Different Memory is allocated for both actual and formal
parameters.
Call by value method
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20. #include<stdio.h>
// function declaration
void swap(int a, int b);
int main()
{
int m = 22, n = 44;
printf(" values before swap m = %d n and n = %d", m, n);
swap(m, n);
}
void swap(int a, int b)
{
int tmp;
tmp = a;
a = b;
b = tmp;
printf(" nvalues after swap m = %dn and n = %d", a, b);
}
Example
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21. • Pass Individual Array Elements
• Pass Arrays to Functions
– Function Prototype: void pass(int []);
– Function call: pass(a);
– Function definition:
• void pass(int b[])
– {for(int i=0;i<3;i++)
– printf("%dn",b[i]);}
Pass arrays to a function in C
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//pass second and third elements to display()
display(ageArray[1], ageArray[2]);
Function Definition
void display(int age1, int age2)
{ // code }

22. 22
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