functions in c

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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