13.Comments in C language

 

Comments in C language:

Any thing written with in /*      */ is called comments.

The compiler will not execute any thing written within comments.

It is only used to write comments on different parts of program.

It is like documentation to other programmers.

 

specification 9:

Accept two numbers into two variables and interchange their values. finally print the values of variables as output.

 

Logic:

When a variable is assigned by another variable, then the original value of variable is overwriting by new value.

We cannot directly assign a variable to another to interchange the values of variables.

We take a temporary variable to interchange the values of two variables.

 

 

 

 

 

 

 

 

Program:

#include<stdio.h>
void main()
{
int x,y,temp;
clrscr();
printf(“Accept a number into x:”);
scanf(“%d”,&x);
printf(“Accept a number into y:”);
scanf(“%d”,&y);
printf("Before swapping::X=%d ,Y=%d \n",x,y);
temp=x;
x=y;
y=temp;
printf("After swapping X=%d,Y=%d \n",x,y);
getch();
}

 

Execution:

Accept a number into x:20

Accept a number into y:45

Before swapping  x=20 , y=45

After swapping x=45 , y=20

 

Example Explained:

20 is assigned to x and 45 is assigned to y

y can’t be directly assigned to x. because, it may overwrite the original value of x.

Hence x is assigned to temp before assigning y to x, in order to hold the original value of x.

temp (value of x) is assigned to y after assigning the value of y to x.

 

specification 10:

Accept two numbers into two variables from the keyboard and print them by interchanging their values without using the temporary variable.

 

Logic:

We can swap the values of two variable using arithmetic operations

 

 

 

 

 

 

 

 

 

Program:

#include<stdio.h>
void main()
{
int x,y;
clrscr();
printf(“Enter the value of x:”);
scanf(“%d”,&x);
printf(“Enter the value of y:”);
scanf(“%d”,&y);
x=x+y;
y=x-y;
x=x-y;
printf(“The value of x: %d”,x);
printf(“\nThe value of y: %d”,y);
getch();
}

 

Execution:

Enter the value of  x: 20

Enter the value of  y: 45

The value of  x: 45

The value of  y: 20

 

Specification 11:

Accept any three digit number and print the sum of all digits.

 

Logic:

The modulo division of any number with 10 is the last digit.

The modulo division of a single digit number with 10 is the same digit.

Division of any integer by another integer is an integer.

 

 

 

 

 

 

 

 

 

 

 

 

 

 Program:

#include<stdio.h>
void main()
{
int n,first,second,third,sum;
clrscr();
printf(“Enter any three digit number:”);
scanf(“%d”,&n);
third=n%10;
n=n/10;
second=n%10;
n=n/10;
first=n%10;
sum=first+second+third;
printf(“Sum of all the digits %d”,sum);
getch();
}

 

Execution:

Enter any three digit number: 345

Sum of all the digits 12

Specification 12:

Accept any three digit number and print it in reverse.

 

Logic:

 

 

 

 

 

 

 

 

 

Program:

#include<stdio.h>
void main()
{
int n,first,second,third,rev;
clrscr();
printf(“Enter any three digit number:”);
scanf(“%d”,&n);
third=n%10;
n=n/10;
second=n%10;
n=n/10;
first=n%10;
rev=third*100+second*10+first*1;
printf(“The reverse number %d”,rev);
getch();
}

EXECUTION:

enter three digits number: 123

The reverse number: 321

 

Specification13:

Accept a four digit number and print the sum of all the digits and the reverse number.

 

Program:

#include<stdio.h>
void main()
{
int n,first,second,third,fourth,sum,rev;
clrscr();
printf("Enter any four digit number:”);
scanf(“%d”,&n);
fourth=n%10;
n=n/10;
third=n%10;
n=n/10;
second=n%10;
n=n/10;
first=n%10;
sum=first+second+third+fourth;
rev=fourth*1000+third*100+second*10+first*1;
printf(“Sum of all the digits %d”,sum);
printf(“\nThe reverse number %d”,rev);
getch();
}

EXECUTION:

Enter any four digit number: 1234

Sum of all the digits: 10

The reverse number: 4321