Basic C Programs for Beginners

The general form of a C program is as follows:

Pre-processor directives
Global declaration
Main()
{
Local variables to function main;
Statements associated with function  main();
}
Fun1()
{
Local variables to function fun1();
Statements associates with function fun1();
}
Fun2()
{
Local variables to function fun2();
Statements associates with function fun2();
}

1. A program to print Hello World.

#include<stdio.h>
/*main function starts here*/
Void main()
{
Printf(“Hello world!\n”);
}

Output: Hello world

2. Using #define in a Program

#include<stdio.h>
#include<conio.h>
#define BELL ‘\a’
Void main()
{
Printf(“Press any key to hear the bell!”);
getch();
printf(“%c”, BELL);
}

Output: Press any key to hear the bell.

3. Using const in a C program

#include<stdio.h>
Void main()
{
Const float PI=3.142857142857;
Float area, perimeter, radius;
Printf(“enter the radius:”);
Scanf(“%f”, &radius);
Area=PI*radius*radius;
Perimeter=2*PI*radius;
Printf(“Area=%f sq. unit and perimeter=%f unit”, area, perimeter);
}

4. Using printf() function in a C program

#include<stdio.h>
Main()
{
Printf(“this is an example of something printed!”);
Return 0;
}

5. Using scanf() function in a C program

#include<stdio.h>
Main()
{
Float y;
Int x;
Puts(“enter a float, then an int”);
Scanf(“%f%d”, &y, &x);
Printf(“\nYou entered %f and %d”, y, x);
Return 0;
}

6. Another simple program in C using int and printf()

#include<stdio.h>
Main()
{
Int a, b, average;
a=10;
b=6;
average=(a+b)/2;
printf(“Here ”);
printf(“is ”);
printf(“the ”);
printf(“answer….. ”);
printf(“\n ”);
printf(“%d ”, average);
}

7. A simple program to Demonstrate scanf() function

#include<stdio.h>
Main()
{
int a, b, c;
printf(“\nThe first number is ”);
scanf(“%d”, &a);
printf(“\nThe second number is ”);
scanf(“%d”, &b);
c=a+b;
printf(“The answer is %d\n”, c);
}

8. A while loop and 100 Hello Worlds

#include<stdio.h>
Main()
{
int count;
count=0;
while(count<100)
{
++count;
Printf(“Hello World!\n”);
}
}

9. The do while loop and a 100 Hello Worlds

#include<stdio.h>
main()
{
int count;
count=0;
do
{
++count;
Printf(“Hello World!\n”);
}
While(count<100);
}

10. This program demonstrates the for loop

#include<stdio.h>
main()
{
int fahr;
for(fahr=0;fahr<=300;fahr=fahr+20)
printf(“%4d%6.1f\n”, fahr, (5.0/9.0)*(fahr-32));
}

11. This program demonstrates the while loop

#include<stdio.h>
Main()
{
Int lower, upper, step;
Float fahr, Celsius;
Lower=0;
Upper=300;
Step=20;
Fahr=lower;
While(fahr<=upper)
{
Celsius=(5.0/9.0)*(fahr-32.0);
Printf(“%d.0f%6.1f\n”, fahr, celsius);
Fahr=fahr+step;
}
}

12. This program demonstrates the if statement

#include<stdio.h>
Main()
{
Int a, b;
Do
{
Printf(“\nEnter first number:”);
Scanf(“%d”, &a);
Printf(“\nEnter second number:”);
Scanf(“%d”, &b);
If(a<b)
printf(“\n\nfirst number is less than second\n\n”);
if(b<a)
printf(“second number is less than first number\n\n”);
}
while(a<999);
}

13. This program demonstrates the if-block

#include<stdio.h>
main()
{
int a, b;
do {
printf(“\nEnter first number:”);
scanf(“%d”, &a);
printf(“\nEnter second number:”);
scanf(“%d”, &b);
if (a<b){
printf(“\n\nFirst number is less than second\n”);
printf(“Their difference is: %d\n”, b-a);
printf(“\n”);
}
printf(“\n”);
}while(a<999);
}

14. The program demonstrates the Use of the if else block

#include<stdio.h>
main()
{
int num1, num2;
printf(“\nEnter the first number”);
scanf(“%d”, &num1);
printf(“\nEnter the second number”);
scanf(“%d”, &num2);
if(num2==0)
printf(“\n\nCannot divide by zero\n\n”);
else
printf(“\n\nAnswer is %d\n\n”, num1/num2);
}

15. A simple program to show the use of continue statement

#include<stdio.h>
main()
{
int x;
for (x=0; x<=100; x++){
if (x%2) continue;
printf(“%d\n”, x);
}
}

16. This program jumps out of an infinite loop using the break statement

#include<stdio.h>
main()
{
int t;
for ( ; ; ){
scanf(“%d”, &t);
if (t==10) break;
}
printf(“End of an infinite loop….\n”);
}

17. This program demonstrates the switch statement

#include<stdio.h>
main()
{
int i;
printf(“Enter a number between 1 and 4”);
scanf(“%d”, &i);
switch(i)
{
case 1;
printf(“One”);
break;
case 2;
printf(“Two”);
break;
case 3;
printf(“three”);
break;
case 4;
printf(“Four”);
break;
default;
printf(“Unrecognized number”);
} /*End of switch*/
}

18. A program in C having No argument with return value

#include<stdio.h>
main()
{
int test(void);
int max;
max=test();
printf(“The maximum of the two is : %d”, max);
}
int test(void)
{
int x, y;
printf(“Enter 1st no.:”);
scanf(“%d”, &x);
printf(“Enter 2nd no.:”);
scanf(“%d”, &y);
return(x>y?x:y);
}

19. A program in C with Argument and with return value

#include<stdio.h>
main()
{
int test(int, int);
int x, y, max;
printf(“Enter 1st no.:”);
scanf(“%d”, &x);
printf(“Enter 2nd no.:”);
scanf(“%d”, &y);
max=test(x,y);
printf(“The maximum of the two is %d”, max);
}
int test(int a, int b)
{
return(a>b?a:b);
}

20. C program having argument with no return value

#include<stdio.h>
main()
{
void test (int, int);
int x, y;
printf(“Enter 1st no.:”);
scanf(“%d”, &x);
printf(“Enter 2nd no.:”);
scanf(“%d”, &y);
test(x,y);
}
void test(int a, int b)
{
int max;
max=a>b?a:b;
printf(“The maximum of the two is: %d”, max);
}

21. A program in C using Call by Value

#include<stdio.h>
main()
{
void swap(int, int);
int a=10, b=20;
swapv(a, b);
printf(“\n a=%d b=%d”, a, b);
}
void swapv(int x, int y)
{
int t;
t=x;
x=y;
y=t;
printf(“\n x=%d y=%d”, x, y);
}

22. A Program in C using Call by reference

#include<stdio.h>
main()
{
void swapr(int *, int *);
int a=10, b=20;
swapr(&a, &b);
printf(“\n a=%d b=%d”, a, b);
}
void swapr(int *x, int *y)
{
int t;
t=*x;
*x=*y;
*y=t;
}

23. Another program in C using Call by reference

#include<stdio.h>
main()
{
void areaperi(int, float *, float *);
int radius;
float area, perimeter;
printf(“Enter radius of a circle:”);
scanf(“%d”, &radius);
areaperi(radius, &area, &perimeter);
printf(“Area=%f”, area);
printf(“\nPerimeter=%f”, perimeter);
}
void areaperi(int r, float *a, float *p)
{
*a=3.14*r*r;
*p=2*3.14*r;
}

24. A program in C of Recursive function to calculate the factorial value of a given interger

#include<stdio.h>
main()
{
int rec(int );
int n, fact;
printf(“Enter an integer to find its factorial value:”);
scanf(“%d”, fact);
fact=rec(n);
printf(“Factorial value=%d”, fact)
}
int rec(int x)
{
int f;
if(x==1)
return(1);
else
f=x*rec(x 1);
return(f);
}

25. A program in C Passing array elements to a function

#include<stdio.h>
main()
{
void display(int );
int i;
int a[]={35, 45, 55, 65, 75};
for (i=0; i<5; i++)
display(a[i]);
}
void display(int m)
{
printf(“%d”, m);
}

26. A program in C passing an entire array into a function

#include<stdio.h>
main()
{
void display(int *);
int a[]={35, 45, 55, 65, 75};
display(&a[0]);
}
void display(int *m)
{
int i;
for(i=0; i<5; i++)
{
printf(“%d”, *m)
}
}

27. A program in C for double dimension array

#include<stdio.h>
#include<conio.h>
main()
{
int a[10][10], i, j, r, c;
clrscr();
printf(“Enter order of matrix:”);
scanf(“%d%d”, &r, &c);
printf(“Enter %d values”, r*c);
for(i=0;i<r;i++)
for(j=0;j<c;j++)
scanf(“%d”, &a[i][j]);
printf(“\n Elements of array a:”);
for(i=0;i<r;i++)
{
printf(“%d\t”, a[i][j]);
}
}
getch();
}

28. A program in C for Matrix Addition

#include<stdio.h>
#include<conio.h>
main()
{
int a[10][1], b[10][10], d[10][10];
int i, j, r, c, p, q;
clrscr();
printf(“Enter order of matrix a:”);
scanf(“%d%d”, &r, &c);
/*accepting values from user*/
printf(“Enter %d values”, r*c);
for(i=0;i<r;i++)
for(j=0;j<c;j++)
scanf(“%d”, &a[i][j]);
printf(“Enter order of matrix b:”);
scanf(“%d%d”, &p, &q);
/*accepting values from user*/
printf(“Enter %d values”, p*q);
for(i=0;i<p;i++)
for(j=0;j<q;j++)
scanf(“%d”, &a[i][j]);
/*printing values*/
printf(“Elements of array a:”);
for(i=0;i<r;i++)
{
printf(“\n”);
for(j=0;j<c;j++)
{
printf(“%d\t”, a[i][j]);
}
}
printf(“Elements of array b:”);
for(i=0;i<p;i++)
{
printf(“\n”);
for(j=0;j<q;j++)
{
printf(“%d\t”, b[i][j]);
}
}
/*if rows and columns of two matrices are equal*/
if(r==p && c==q)
{
for(i=0;i<r;i++)
{
for(j=0;j<q;j++)
d[i][j]=a[i][j]+b[i][j];
}
printf(“\nElements of array d:”);
for(i=0;i<p;i++)
{
printf(“\n”);
for(j=0;j<q;j++)
{
printf(“%d\t”, d[i][j]);
}
}
}
else
printf(“\nAddition is not possible”);
getch();
}

29. A program in C to obtain the memory address of a variable

#include<stdio.h>
main()
{
int i=5;
int *j; /*here we are declaring the pointer variable*/
j=&i; /*assigning the memory address of i into j*/
printf(“\n Address of i=%u”, &i);
printf(“\n Address of j=%u”, &j);
printf(“\n Value of j=%u”, j);
printf(“\n Value of i=%u”, i);
printf(“\n Value of i=%u”, * j);
}

30. A program in C to demonstrate pointer use

#include<stdio.h>
/*Declare and initialize an int variable*/
/*Declare a pointer to int*/
int *ptr;
main()
{
/*initialize ptr to pointer to var*/
ptr=&var;
/*Access var directly and indirectly*/
printf(“\nDirect access, var=%d”, var);
printf(“\n Indirect access, var=%d”, *ptr);
/*Display the address of var two ways*/
printf(“\n\nThe address of var=%d”, &var);
printf(“\nThe address of var=%d”, ptr);
return 0;
}

31. A program in C to demonstrate pointer to pointer concept

#include<stdio.h>
#include<conio.h>
main()
{
int i=5;
int *j;
int **k;
j=&I;
k=&j;
printf(“\n Address of i=%u”, &i);
printf(“\n Address of i=%u”, j);
printf(“\n Address of i=%u”, *k);
printf(“\n Address of j=%u”, &j);
printf(“\n Address of j=%u”, k);
printf(“\n Value of j=%u”, j);
printf(“\n Value of k=%u”, k);
printf(“\n Value of i=%d”, i);
printf(“\n Value of i=%d”, *j);
printf(“\n Value of i=%u”, **k);
}

32. A program in C for pointer with Arrays

#include<stdio.h>
#include<conio.h>
main()
{
int a[20], d, I;
int *ptr;
clrscr();
printf(“enter dimension:”);
scanf(“%d”, &d);
printf(“\nEnter %d values:”, d);
for (I=0; I<d:I++)
scanf(“%d”, &a[I]);
ptr=a;
printf(“\nElements of array a:\n”);
for(I=0;I<d;I++)
{
printf(“%d\t”, *ptr);
ptr++;
}
getch();
}

33. A program in C to demonstrate pointer and multidimensional arrays

#include<stdio.h>
#include<conio.h>
int multi[2][4];
main()
{
printf(“\nmulti=%u”, multi);
printf(“\nmulti[0]=%u”, multi[0]);
printf(“&multi[0][0]=%u\n”, &multi[0][0]);
return 0;
}

34. Another simple program in C, using pointers

#include<stdio.h>
#include<conio.h>
main()
{
float a=10;
float *points_to_a=&a;
printf(“The value in a:%f\n”, a);
printf(“The value pointed to by points_to_a:%f\n”, *points_to_a);
printf(“The value of points_to_a in hex:%x\n”, points_to_a);
printf(“The value of points_to_a as an integer:%d\n”, points_to_a);
printf(“The value of points_to_a as a float:%f\n”, points_to_a);
*points_to_a=-10;
printf(“The value pointed to by points_to_a:%f\n”, *points_to_a);
printf(“The value of points_to_a in hex:%x\n”, points_to_a);
printf(“The value of points_to_a as an integer:%d\n”, points_to_a);
printf(“The value of points_to_a as a float:%f\n”, points_to_a);
exit(0);
}

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