1. Tejalal Choudhary “C Programming from Scratch” Function & its types
Declare
Call
Define
“C Programming from Scratch”
Function & its types
Tejalal Choudhary
Department of Computer Science & Engg
SDBCT, Indore

2. Contents What is function ? Why function ? Library function
User defined function
Header File Creation

3. Scenario 1
Call mechanic

4. Scenario 2
Call electrician

5. Function
Self-contained block of statements that perform a specific task.
Any C program contains at least one function.
One function can call another function
When called function has done its thing, control returns to main( ) function
nobody is nobody’s boss.
function gets called when the function name is followed by a semicolon.
A function is defined when function name is followed by a pair of braces
A function can be called any number of times.
A function can call itself.
Function cannot be defined inside another function.

6. Why function? Function avoids rewriting the same code over and over.
Easier to write programs and keep track of what they are doing.
Easier to manage and debug

7. printf(), scanf(), clrscr(), getch()
Types of function
Function Types
Library Functions
User Defined Functions
printf(), scanf(), clrscr(), getch()

8. Three things about function
Library function
User defined function
Function declaration
No need
Need to declare
Function definition
Need to define
Function call
Need to call

9. int p=pow(2,3); { statement 1; statement 2; ……. }
Function call: getch();
int p=pow(2,3);
Function/Prototype declaration:
return-type function-name(arguments list);
Function definition
return-type function-name(arguments list) {
statement 1;
statement 2;
…… }

10. Actual & formal arguments
Actual arguments
These are the actual values passed during function call
int a=10, b=20;
int r=pow(a,b);
Formal arguments
The variables used during function definition
return-type function-name(int x, int y) {
……. }
a & b actual arguments
x & y formal arguments

11. Return keyword
Return the control to caller
Return the value

12. User defined function types
Based on return type and arguments
No return & no arguments
No return & arguments
Return & no arguments
Return & arguments
void sum();
void sum(int, int);
int sum();
int sum(int, int);

13. Scope of function void main( ) { int a = 100 ; printa( a ) ; }
void printa( int b)
int c = a+b;
printf ( "\n sum=%d", c ) ;

14. Function calling convention
Changes made to the formal arguments in the called function have no effect on actual arguments in the calling function.
Call by value
When we call function as :
int a, b;
sum(a,b); //values of a & b will be passed
Call by reference