C Program to Swap two no’s without using third variable

Program to show swap of two no’s without using third variable

#include<stdio.h>
#include<conio.h>

void main()
{
int a,b;

clrscr();

printf("nEnter value for num1 & num2 : ");
scanf("%d %d",&a,&b);

a=a+b;
b=a-b;
a=a-b;

printf("nAfter swapping value of a : %d",a);
printf("nAfter swapping value of b : %d",b);

getch();
}

Output :

Enter value for num1 & num2 : 10 20

After swapping value of a : 20
After swapping value of b : 10

C Program to reverse a given number !

#include<stdio.h>
#include<conio.h>

void main()
{
int num,rem,rev=0;
clrscr();

printf("nEnter any no to be reversed : ");
scanf("%d",&num);

 while(num>=1)
    {
    rem = num % 10;
    rev = rev * 10 + rem;
    num = num / 10;
    }

printf("nReversed Number : %d",rev);
getch();
}

Output :

Enter any no to be reversed : 123
Reversed Number : 321

C Program to Implement Calender Program to display Day of the month

Calender Program in C Programming Language : Display Day of the month

Calender Program in C Programming Language :

Program will accept Year,Month and Date from the user and will display the day of the month.

#include<stdio.h>
#include<conio.h>
#include<math.h>

int isdatevalid(int month, int day, int year)
{
  if (day <= 0) return 0 ;
  switch( month )
    {
      case 1:
      case 3:
      case 5:
      case 7:
      case 8:
      case 10:
      case 12: if (day > 31) return 0 ; else return 1 ;
      case 4:
      case 6:
      case 9:
      case 11: if (day > 30) return 0 ; else return 1 ;
      case 2:
        if ( day > 29 ) return 0 ;
        if ( day < 29 ) return 1 ;

    else return 0 ;
    }
  return 0 ;
}
//------------------------------------------------
int fm(int date, int month,int year)
{
int fmonth,leap;

//leap function 1 for leap & 0 for non-leap

if((year%100==0) && (year%400!=0))
    leap=0;
else if(year%4==0)
    leap=1;
else
    leap=0;

fmonth=3+(2-leap)*((month+2)/(2*month))+(5*month+month/9)/2;
//f(m) formula

fmonth = fmonth % 7; //bring it in range of 0 to 6

return fmonth;
}

//----------------------------------------------
int day_of_week(int date, int month, int year)
{
int dow; //day of week

int YY = year % 100;
int century = year / 100;

printf("nDate: %d/%d/%dnn",date,month,year);

dow = 1.25 *  YY + fm(date,month,year) + date - 2*( century % 4);
//function of weekday for Gregorian

dow = dow % 7; //remainder on division by 7

switch (dow)
    {
    case 0:
        printf("weekday = Saturday");
        break;
    case 1:
        printf("weekday = Sunday");
        break;
    case 2:
        printf("weekday = Monday");
        break;
    case 3:
        printf("weekday = Tuesday");
        break;
    case 4:
        printf("weekday = Wednesday");
        break;
    case 5:
        printf("weekday = Thursday");
        break;
    case 6:
        printf("weekday = Friday");
        break;
    default:
        printf("Incorrect data");
    }
return 0;
}
//------------------------------------------
void main()
{
int date,month,year;
clrscr();

printf("Enter the year ");
scanf("%d",&year);

printf("Enter the month ");
scanf("%d",&month);

printf("Enter the date ");
scanf("%d",&date);

day_of_week(date,month,year);

getch();
}

Output :

Enter the year 2012
Enter the month 02
Enter the date 29

Date: 29/2/2012

weekday = Wednesday

C Program to find Factorial of Number without using function

Find Factorial of Number without using function

#include<stdio.h>
#include<conio.h>
void main()
{
int i,number,factorial;
printf("nEnter the number : ");
scanf("%d",&n);

factorial = 1;
for(i=1;i<=n;i++)
      factorial = factorial * i;

printf("nFactorial of %d is %d",n,factorial );
getch();
}

Output :

Enter the number : 5
Factorial of 5 is 120

Explanation of Program :

Before Explaining the program let us see how factorial is calculated -

Factorial of 5 = 5!
               = 5 * 4!
               = 5 * 4  * 3!
               = 5 * 4  * 3 * 2!
               = 5 * 4  * 3 * 2 * 1!
               = 5 * 4  * 3 * 2 * 1 * 0!
               = 5 * 4  * 3 * 2 * 1 * 1
               = 120

Firstly accept the number whose factorial is to be found.

printf("nEnter the number : ");
scanf("%d",&n);

We have to iterate from 1 to (n-1) using for/while/do-while loop. In each iteration we are going to multiply the current iteration number and result.

for(i=1;i<=n;i++)
      factorial = factorial * i;

Some Precautions to be taken :

Precaution 1 : Initialize ‘factorial’ variable

factorial = 1;

before going inside loop we must initialize factorial variable to 1 since by default each c variable have garbage value. If we forgot to initialize variable then garbage value will be multiplied and you will get garbage value as output.

Precaution 2 : For loop must start with 1

Suppose by mistake we write following statement -

for(i=0;i<=n;i++)
      factorial = factorial * i;

then in the very first iteration we will get factorial = 0 and in all successive iteration we will get result as 0 since anything multiplied by Zero is Zero

Precaution 3 : Try to accept lower value to calculate factorial

We have 2 bytes to store the integer in Borland C++ compiler, so we can have maximum limit upto certain thousand. Whenever we try to accept value greater than 20 we will get factorial overflow.

C Program to print table of n and square of n using pow()

Print Table of n and Square of n

#include<stdio.h>
#include<conio.h>
void main()
{
      int n;
      printf("Not Squaren");
      printf("-----------------n");
      for(n=1;n <=10;n++)
          printf("%dt%dn",n,n*n);
      getch();
}

Output :

 No Square
 -------------
  1 1
  2 4
  3 9
  4 16
  5 25
  6 36
  7 49
  8 64
  9 81
 10 100

Explanation of Program :

We can alternately write above program like this -

printf("%dt%dn",n,pow(n,2));

In order to use above line in the code we need to include math.h header file inside C program.

#include<math.h>

Alternate Way Using Pow :

#include<stdio.h>
#include<conio.h>
#include<math.h>

void main()
{
      int n;
      printf("Not Squaren");
      printf("-----------------n");
      for(n=1;n <=10;n++)
          printf("%dt%dn",n,pow(n,2));
      getch();
}

Find Factorial of Number Using Recursion

#include<stdio.h>
#include<conio.h>
int fact(int);
void main()
{
 int x,n;
 printf("nEnter the value of n :");
 scanf("%d",&n);
 x=fact(n);
 printf("n%d",x);
 getch();
}
int fact(int n)
{
 if(n==0)
  return(1);
 return(n*fact(n-1));
}