Functions in C allow programmers to organize code into self-contained blocks that perform specific tasks. A function is defined with a name and can accept parameters. The main() function is where program execution begins. Several examples are provided that demonstrate defining and calling functions to perform tasks like addition, incrementing values, and displaying output. Functions can access variables in their own scope as well as variables passed into them as parameters.

1. C Programming - Functions
Organized By: Vinay Arora
Assistant Professor, CSED
Thapar University, Patiala

2. Main program & its sub parts
Function is also known as sub-program or module.
Function is a self contained block of statements that perform coherent task of
some kind.
Vinay Arora
CSED

3. Program-1
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
printf("n Message for You");
printf("n Department of Civil Engineering");
getch();
}
Vinay Arora
CSED

4. Program-1 (output)
Vinay Arora
CSED

5. Program-2
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
message();
printf("n Department of Civil Engineering");
getch();
}
message()
{
printf("n Message for You");
}
Vinay Arora
CSED

6. Program-2 (output)
Vinay Arora
CSED

7. Program-3
#include<stdio.h>
#include<conio.h>
void message();
void main()
{
clrscr();
message();
printf("n Department of Civil Engineering");
getch();
}
void message()
{
printf("n Message for You");
}
Vinay Arora
CSED

8. Program-3 (output)
Vinay Arora
CSED

9. Program-4
#include<stdio.h> void civil()
#include<conio.h> {
printf("nCivil Engg.");
void civil(); }
void computer();
void electronics(); void computer()
{
void main() printf("nComputer Engg.");
{ }
clrscr();
void electronics()
civil(); {
computer(); printf("nElectronics Engg.");
electronics(); }
printf("nnDepartments at Thapar");
getch();
}
Vinay Arora
CSED

10. Program-4
#include<stdio.h> void civil()
#include<conio.h> {
printf("nCivil Engg.");
void civil(); }
void computer();
void electronics(); void computer()
{
void main() printf("nComputer Engg.");
{ }
clrscr();
void electronics()
civil(); {
computer(); printf("nElectronics Engg.");
electronics(); }
printf("nnDepartments at Thapar");
getch();
}
Vinay Arora
CSED

11. Program-4 (output)
Vinay Arora
CSED

12. Program-5
#include<stdio.h> void civil()
#include<conio.h> {
printf("nCivil Engg.");
void civil(); computer();
void computer(); }
void electronics();
void computer()
void main() {
{ printf("nComputer Engg.");
clrscr(); electronics();
}
civil();
void electronics()
printf("nnDepartments at Thapar"); {
printf("nElectronics Engg.");
getch(); }
}
Vinay Arora
CSED

13. Program-5
#include<stdio.h> void civil()
#include<conio.h> {
printf("nCivil Engg.");
void civil(); computer();
void computer(); }
void electronics();
void computer()
void main() {
{ printf("nComputer Engg.");
clrscr(); electronics();
}
civil();
void electronics()
printf("nnDepartments at Thapar"); {
printf("nElectronics Engg.");
getch(); }
}
Vinay Arora
CSED

14. Program-5 (output)
Vinay Arora
CSED

15. Program-6
#include<stdio.h> void civil()
#include<conio.h> {
printf("nCivil Engg.");
void civil(); }
void main()
{
clrscr();
civil();
civil();
printf("nnDepartments at Thapar");
getch();
}
Vinay Arora
CSED

16. Program-6
#include<stdio.h> void civil()
#include<conio.h> {
printf("nCivil Engg.");
void civil(); }
void main()
{
clrscr();
civil();
civil();
printf("nnDepartments at Thapar");
getch();
}
Vinay Arora
CSED

17. Program-6 (output)
Vinay Arora
CSED

18. Program-7
#include<stdio.h>
#include<conio.h>
void main()
{
int a,b,c;
clrscr();
printf("Enter Numbers for Additionn");
printf("Enter 1st Number:t");
scanf("%d",&a);
printf("Enter 2nd Number:t");
scanf("%d",&b);
c=a+b;
printf("Result after Addition is:%d",c);
getch();
}
Vinay Arora
CSED

19. Program-7 (output)
Vinay Arora
CSED

20. Program-8
#include<stdio.h> void sum()
#include<conio.h> {
int a,b,c;
void sum(); printf("Enter Numbers for Additionn");
void main() printf("Enter 1st Number:t");
{ scanf("%d",&a);
clrscr(); printf("Enter 2nd Number:t");
sum(); scanf("%d",&b);
getch();
} c=a+b;
printf("Result after Addition is:%d",c);
}
Vinay Arora
CSED

21. Program-8 (output)
Vinay Arora
CSED

22. Program-9
#include<stdio.h> void sum(int x,int y)
#include<conio.h> {
int z;
void sum(); z=x+y;
void main() printf("Result after Addition is:%d",z);
{ }
int a,b,c;
clrscr();
printf("Enter Numbers for Additionn");
printf("Enter 1st Number:t");
scanf("%d",&a);
printf("Enter 2nd Number:t");
scanf("%d",&b);
sum(a,b);
getch();
}
Vinay Arora
CSED

23. Program-9 (output)
Vinay Arora
CSED

24. Program-10
#include<stdio.h> int sum(int x,int y)
#include<conio.h> {
int z;
int sum(); z=x+y;
void main() return (z);
{ }
int a,b,c;
clrscr();
printf("Enter Numbers for Additionn");
printf("Enter 1st Number:t");
scanf("%d",&a);
printf("Enter 2nd Number:t");
scanf("%d",&b);
c=sum(a,b);
printf("Result after Addition is:%d",c);
getch();
}
Vinay Arora
CSED

25. Program-10 (output)
Vinay Arora
CSED

26. Program-11
#include<stdio.h> int increment(int x)
#include<conio.h> {
x++;
int increment(); return (x);
void main() }
{
int a,b,c;
clrscr();
printf("Enter Numbert");
scanf("%d",&a);
c=increment(a);
printf("Result after Increment will be:%d",c);
getch();
}
Vinay Arora
CSED

27. Program-11 (output)
Vinay Arora
CSED

28. Program-12
#include<stdio.h>
#include<conio.h>
void display();
void main()
{
int a=20;
clrscr();
display(a);
getch();
}
void display(int x)
{
int y=27;
printf("Value passed from main function is %dn",x);
printf("Value present in display function is %d",y);
}
Vinay Arora
CSED

29. Program-12 (output)
Vinay Arora
CSED

30. Program-13
#include<stdio.h> void display()
#include<conio.h> {
int x=25;
void display();
void main() printf("Value of x in display function is %d",x);
{ }
int x=20;
clrscr();
printf("Value of x in main function %dn",x);
display();
getch();
}
Vinay Arora
CSED

31. Program-13 (output)
Vinay Arora
CSED

32. Program-14
#include<stdio.h> void display(int x)
#include<conio.h> {
x=77;
void display();
void main() printf("Value of x in display function is %d",x);
{ }
int x=20;
clrscr();
printf("Value of x in main function %dn",x);
display();
getch();
}
Vinay Arora
CSED

33. Program-14 (output)
Vinay Arora
CSED

34. Program-15
#include<stdio.h> int increment(int a)
#include<conio.h> {
a++;
void display(); return (a);
void main() }
{
int a,b; int decrement(int a)
clrscr(); {
a--;
printf("Enter Numbert"); return (a);
scanf("%d",&a); }
b=increment(a);
printf("nValue after increment is %dt",b);
b=decrement(a);
printf("nValue after decrement is %dt",b);
getch();
}
Vinay Arora
CSED

35. Program-15 (output)
Vinay Arora
CSED

36. Program-17
#include<stdio.h>
#include<conio.h>
int increment();
void main()
{
int i=10,j=20,k=30;
clrscr();
printf("%dt%dt%dn",i,j,k);
printf("%dt%dt%dn",i,j);
printf("%dn",i,j);
getch();
}
Vinay Arora
CSED

37. Program-17 (output)
Vinay Arora
CSED

38. Program-18
#include<stdio.h>
float square(float x)
#include<conio.h>
{
float y;
float square(float);
y=x*x;
void main()
return(y);
{
}
float a,b;
clrscr();
printf("Enter any Number:");
scanf("%f",&a);
b=square(a);
printf("Square of number entered is %ft",b);
getch();
}
Vinay Arora
CSED

39. Program-18 (output)
Vinay Arora
CSED

40. Program-19
#include<stdio.h> int factorial(int x)
#include<conio.h> {
int f=1,i;
void main()
{ for(i=x;i>=1;i--)
int a,fact; f=f*i;
clrscr();
return(f);
printf("Enter any Number:"); }
scanf("%d",&a);
fact=factorial(a);
printf("Factorial Value is = %dn",fact);
getch();
}
Vinay Arora
CSED

41. Program-19 (output)
Vinay Arora
CSED

42. Program-20 (Recursion in C)
#include<stdio.h> int rec(int x)
#include<conio.h> {
int f;
int rec(int);
void main() if(x==1)
{ return(1);
int a,fact; else
clrscr(); f=x*rec(x-1);
printf("Enter any Number:"); return(f);
scanf("%d",&a); }
fact=rec(a);
printf("Factorial Value is = %dn",fact);
getch();
}
Vinay Arora
CSED

43. Recursion
Vinay Arora
CSED

44. Program-20 (output)
Vinay Arora
CSED

45. Program-21
#include<stdio.h>
#include<conio.h>
void main()
{
int i;
clrscr();
for(i=0;i<=50000;i++)
printf("%dn",i);
getch();
}
Vinay Arora
CSED

46. Program-21 (output)
Vinay Arora
CSED

47. Program-22
#include<stdio.h> void val()
#include<conio.h> {
i=100;
int i=0; printf("Val's i=%dn",i);
void val(); i++;
}
void main()
{
clrscr();
printf("Main's i=%dn",i);
i++;
val();
printf("Main's i=%dn",i);
val();
getch();
}
Vinay Arora
CSED

48. Program-22 (output)
Vinay Arora
CSED

49. Program-23
#include<stdio.h>
#include<conio.h>
void main()
{
int count=5;
clrscr();
printf("Count=%dn",count);
count--;
if(count>0)
main();
else
exit();
getch();
}
Vinay Arora
CSED

50. Program-23 (output)
INFINITE LOOP
Vinay Arora
CSED

51. Program-24
#include<stdio.h> int g(int x)
#include<conio.h> {
int v=1;
int g(int); int b=3;
void main()
{ v+=x;
int i,j; return(v+x+b);
clrscr(); }
for(i=1;i<5;i++)
{
j=g(i);
printf("%dn",j);
}
getch();
}
Vinay Arora
CSED

52. Program-24 (output)
Vinay Arora
CSED

53. Program-25
#include<stdio.h>
#include<conio.h>
int x=10;
void main()
{
int x=20;
clrscr();
{
int x=30;
printf("%dn",x);
}
printf("%dn",x);
getch();
}
Vinay Arora
CSED

54. Program-25 (output)
Vinay Arora
CSED

55. Program-26
#include<stdio.h> void func()
#include<conio.h> {
int i,j,k;
void func(); i=j=k=0;
void main()
{ i++;j++;k++;
clrscr(); printf("%d%d%dn",i,j,k);
func(); }
func();
getch();
}
Vinay Arora
CSED

56. Program-26 (output)
Vinay Arora
CSED

57. Thnx…
Vinay Arora
CSED