Loop Control Structures – Theory and Programs [Learn to code]

What are loop control structures? Learn syntax for Loop Control Structures, types of loops and different programs on Loop Control Structures.

• 025. Write a Program to print numbers 1 to n using while loop in C language

  #include<stdio.h>
  #include<conio.h>   
  main()
  {
    int i=1,n;
    clrscr();
    printf("Enter n : ");
    scanf("%d",&n);
    while(i<=n)
    {
  	   printf("%d\t",i);
  	   i++;
    }
    getch();
  }
  
  
  

• 026. Write a Program to print numbers n to 1 using Do While loop in C language

  #include<stdio.h>
  #include<conio.h>   
  main()
  {
    int i=1,n;
    clrscr();
    printf("Enter n : ");
    scanf("%d",&n);
    i=n;
    do
    {
  	   printf("%d\t",i);
  	   i--;
    }while(i>=1);
    getch();
  }
  
  
  
  

• 027. Write a Program to print first n even numbers in C language

  #include<stdio.h>
  void main()
  {
      int i=1,n,counter=2;
      printf("Enter n : ");
      scanf("%d",&n);
    
      while(i<=n)
      {
          printf("%d\t",counter);
          counter = counter + 2;
          i++;
      }
  }
  

• 028. Write a Program to print first n odd numbers in C language

  #include<stdio.h>
  void main()
  {
      int i=1,n,counter=1;
      printf("Enter n : ");
      scanf("%d",&n);
   
      while(i<=n)
      {
          printf("%d\t",counter);
          counter = counter + 2;
          i++;
      }
  }
  

• 029. Write a Program to accept a number and print the number in reverse order. E.g. if 1324 is the number then the output will be 4231 in C language

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
    int rem,n;
    clrscr();
    printf("Enter n : ");
    scanf("%d",&n);
    while(n>0)
    {
  	   rem=n%10;
  	   printf("%d",rem);
  	   n=n/10;
    }
    getch();
  }
  
  
  

• 030. Write a Program to accept a number and print sum of it’s digits in C language

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
    int rem,sum=0,n
    clrscr();
    printf("Enter n : ");
    scanf("%d",&n);
    while(n>0)
    {
  	   rem=n%10;
  	   sum=sum+rem;
  	   n=n/10;
    }
    printf("Sum of digits....%d",sum);
    getch();
  }
  
  
  

• 031. Write a program to accept a number from user and check if it is Armstrong number or not i.e. 153 = 1^3 + 5^3 + 3^3 = 153 in C language

  #include
  #include
  main()
  {
    int temp,rem,sum=0,n;
    clrscr();
    printf("Enter n : ");
    scanf("%d", &n);
    temp=n;
    while(n > 0)
    {
  	   rem=n%10;
  	   sum=sum+rem*rem*rem;
  	   n=n/10;
    }
    if(temp==sum)
  		printf("Armstrong Number");
    else
  		printf("Not an Armstrong Number");
    getch();
  }
  
  
  

• 032. Write a program to print table of a given number n in C language

  #include<stdio.h>
  #include<conio.h>  
  main()
  { 
   int i,n;
   clrscr();
   printf("Enter number : ");
   scanf("%d",&n);
   for(i=1;i<=10;i++)
  	printf("%d X %d = %d\n",n,i,n*i);
   getch();
  }
  
  
  

• 033. Write a program to print sum of given first n numbers in C language

  #include<stdio.h> 
  #include<conio.h>  
  main()
  {
   int n,newn,i,sum=0;
   clrscr();
   printf("Enter number : ");
   scanf("%d",&n);
   printf("Numbers entered....\n");
   for(i=1;i<=n;i++)
   {
  	scanf("%d",&newn);
  	sum=sum+newn;
   }
   printf("Sum of given n digits is... %d",sum);
  }
  
  
  

• 034. Write a program to print following outputs in C language

  * * * * * *
  * * * * * *
  * * * * * *
  * * * * * *
  * * * * * *
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	for(i=1;i<=n;i++)
  	{
  		for(j=1;j<=n;j++)
  			{
  			 printf("*");
  			}
  		printf("\n");
  	}
  	getch();
  }
  
  
  
  

• 035. Write a program to print following outputs in C language

  *
  * *
  * * *
  * * * *
  * * * * *
  

   
  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	for(i=1;i<=n;i++)
  	{
  		for(j=1;j<=i;j++)
  			{
  			 printf("*");
  			}
  		printf("\n");
  	}
  	getch();
  }
  
  
  

• 036. Write a program to print following outputs in C language

  * * * * *
  * * * *
  * * *
  * *
  *
  

  #include<stdio.h> 
  #include<conio.h>  
  main()
  {
  	int i,j,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	for(i=n;i>=1;i--)
  	{
  		for(j=1;j<=i;j++)
  			{
  			 printf("*");
  			}
  		printf("\n");
  	}
  	getch();
  }
  
  
  

• 037. Write a program to print following outputs in C language

  * * * * *
    * * * *
      * * *
        * *
          *
  

  #include<stdio.h> 
  #include<conio.h>  
  main()
  {
  	int i,j,k,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	for(i=1;i<=n;i++)
  	{
  		for(k=1;k<i;k++)
  			{
  			 printf(" ");
  			}
  		for(j=i;j<=n;j++)
  			{
  			 printf("*");
  			}
  		printf("\n");
  	}
  	getch();
  }

• 038. Write a program to print following outputs in C language

          *
        * *
      * * *
    * * * *
  * * * * *
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,k,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	for(i=n;i>=1;i--)
  	{
  		for(k=1;k<=(n-i);k++)
  			{
  			 printf(" ");
  			}
  		for(j=1;j<=i;j++)
  			{
  			 printf("*");
  			}
  		printf("\n");
  	}
  	getch();
  }
  
  
  

• 039. Write a program to print following outputs in C language

          *
        * * *
      * * * * *
    * * * * * * *
  * * * * * * * * *
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,k,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	for(i=1;i<=n;i++)
  	{
  		for(k=1;k<=(n-i);k++)
  			{
  			 printf(" ");
  			}
  		for(j=1;j<=i;j++)
  			{
  			 printf("*");
  			}
  		for(j=2;j<=i;j++)
  			{
  			 printf("*");
  			}
  
  		printf("\n");
  	}
  	getch();
  }
  
  
  

• 040. Write a program to print following outputs in C language

  * * * * * * * * *
    * * * * * * *
      * * * * *
        * * *   
          *
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,k,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	for(i=n;i>=1;i--)
  	{
  		for(k=1;k<=(n-i);k++)
  			{
  			 printf(" ");
  			}
  		for(j=1;j<=i;j++)
  			{
  			 printf("*");
  			}
  		for(j=2;j<=i;j++)
  			{
  			 printf("*");
  	}
  
  		printf("\n");
  	}
  	getch();
  }
  
  
  

• 041. Write a program to print following outputs in C language

          *
        * * *
      * * * * *
    * * * * * * *
  * * * * * * * * *
    * * * * * * *
      * * * * *
        * * *   
          *
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,k,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  
  	for(i=1;i<=n;i++)
  	{
  		for(k=1;k<=(n-i);k++)
  			{
  			 printf(" ");
  			}
  		for(j=1;j<=i;j++)
  			{
  			 printf("*");
  			}
  		for(j=2;j<=i;j++)
  			{
  			 printf("*");
  			}
  
  		printf("\n");
  	}
  
  	for(i=n-1;i>=1;i--)
  	{
  		for(k=1;k<=(n-i);k++)
  			{
  			 printf(" ");
  			}
  		for(j=1;j<=i;j++)
  			{
  			 printf("*");
  			}
  		for(j=2;j<=i;j++)
  			{
  			 printf("*");
  			}
  
  		printf("\n");
  }
  	getch();
  }
  
  
  

• 042. Write a program to print following outputs in C language

  1
  12
  123
  1234
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,k,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	for(i=1;i<=n;i++)
  	{
  		for(j=1;j<=i;j++)
  			printf("%d",j);			
  		printf("\n");
  	}
  	getch();
  }
  
  
  

• 043. Write a program to print following outputs in C language

  1
  22
  333
  4444
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,k,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	for(i=1;i<=n;i++)
  	{
  		for(j=1;j<=i;j++)
  			printf("%d",i);
  		printf("\n");
  	}
  	getch();
  }
  
  
  

• 044. Write a program to print following outputs in C language

     A
    BBB
   CCCCC
  DDDDDDD
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,k,n;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	//ASCII Code for 'A' is 65
  	for(i=1;i<=n;i++)
  	{
  		for(k=1;k<=(n-i);k++)
  			{
  			 printf(" ");
  			}
  		for(j=1;j<=i;j++)
  			{
  			 printf("%c",64+i);
  			}
  		for(j=2;j<=i;j++)
  			{
  			 printf("%c",64+i);
  			}
  
  		printf("\n");
  	}
  	getch();
  }
  
  
  

• 045. Write a program to print following outputs in C language

  ABCDEEDCBA
  ABCD  DCBA
  ABC    CBA
  AB      BA
  A        A
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
    int i,n,j,k;
    clrscr();
    printf("Enter number........");
    scanf("%d",&n);
    for(i=n-1;i>=0;i--)
    {
  		for(j=0;j<=i;j++)
  			printf("%c",65+j);
  		for(k=1;k<(n-i);k++)
  			printf("  ");
  		for(j=i;j>=0;j--)
  			printf("%c",65+j);
  	printf("\n");
    }
    getch();
  }
  
  
  
  

• 046. Write a program to print following outputs in C language

  1
  11
  121
  1231
  12341
  123451
  

  
  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,n;
  	clrscr();
  	printf("Enter number...");
  	scanf("%d",&n);
  	for(i=0;i<=n;i++)
  	{
  		for(j=1;j<=i;j++)
  		{
  			printf("%d",j);
  		}
  		printf("1\n");
  	}
  	getch();
  }
  
  

• 047. Write a program to accept a number from user and print it’s factorial in C language

  Eg: factorial of 5 is:-
  5! = 5 * 4 * 3 * 2 * 1=120

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,fact=1,n;
  	clrscr();
  	printf("Enter number...");
  	scanf("%d",&n);
  	for(i=1;i<=n;i++)
  		fact=fact*i;
  	printf("facttorialof the given number is...%d",fact);
  	getch();
  
  }
  

• 048. Write a program to accept a number from user and print if it is prime or not in C language

  #include<conio.h>  
  #include<process.h>
  main()
  {
  	int i,n;
  	clrscr();
  	printf("Enter number...");
  	scanf("%d",&n);
  	for(i=2;i<=n/2;i++)
  	{
  		if(n%i==0)
  		{
  		printf("Not Prime");
  		getch();
  		exit(0);
  		}
  	}
  	printf("Prime ");
  	getch();
  }
  
  
  

• 049. Write a program to accept a number and print prime numbers between 2 and n in C language

  
  #include<stdio.h>
  #include<conio.h>  
  #include<process.h>
  main()
  {
  	int i,flag=1,n,newn;
  	clrscr();
  	printf("Enter number...");
  	scanf("%d",&n);
  	for(newn=2;newn<=n;newn++)
  	{
  		flag=1;
  		for(i=2;i<=newn/2 ;i++)
  		{
  			if(newn%i==0)
  			{
  			flag=0;
  			break;
  			}
  		}
  		if(flag==1)
  			printf("%d ",newn);
  	}
  	getch();
  }
  
  

• 050. Write a program to accept a number and print fibonacci series upto that level in C language

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int pre=1,cur=1,temp,i,n;
          clrscr();
  	printf("Enter number...");
  	scanf("%d",&n);
  	printf("%d\t%d",pre,cur);
  	for(i=3;i<=n;i++)
  		{
  		 temp=cur;
  		 cur=pre+cur;
  		 pre=temp;
  		 printf("\t%d",cur);
  		}
  	getch();
  }
  
  
  

• 051. Write a program to print digits, alphabets in capital and lower case in C language

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i;
  	clrscr();
  	for(i=65;i<=90;i++)
  		  printf("%c  ",i);
  
  	printf("\n\n\n\n");
  	for(i=97;i<=122;i++)
  		  printf("%c  ",i);
  
  	printf("\n\n\n\n");
  	for(i=48;i<=57;i++)
  		  printf("%c\t",i);
  
  	getch();
  }
  
  
  

• 052. Write a program to accept a number n from user and Add n terms of the series in C language

  1/2! + 2/3! + 3/4! + 4/5! + 5/6! + ………

  
  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j,n;
  	float sum=0,fact=1;
  	clrscr();
  	printf("Enter number....");
  	scanf("%d",&n);
  	for(i=1;i<=n;i++)
  	{
  		fact=1;
  		for(j=1;j<=i+1;j++)
  			fact=fact*j;
  	sum=sum+i/fact;
  	}
  	printf("Sum of the series....%f",sum);
  	getch();
  }
  
  
  
  

• 053. Write a program to read n numbers (Xi) from the user and print out their average and standard deviation. Formulae are

  Average = (Sum of Xi)/n

  
  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int n,i,newn,sum_avg=0;
  	float avg;
  	clrscr();
  	printf("Enter number : ");
  	scanf("%d",&n);
  	printf("Enter numbers...");
  	for(i=1;i<=n;i++)
  	{
  		scanf("%d",&newn);
  		sum_avg=sum_avg+newn;
  	}
  	avg=sum_avg/(float)n; //Type casting.
  
  	printf("\nAverage = %f",avg);
  	getch();
  }
  

• 054. Write a program to print out ASCII chart on a single screen (all 256 characters from 0 to 255) in a tabular form. The ASCII code should be followed by the corresponding character in C language

  
  #include<stdio.h>
  #include<conio.h>  
  main()
  {
   int i;
   clrscr();
   for(i=0;i<=255;i++)
  	printf("%d-%c\t",i,i);
   getch();
  }
  
  
  

• 055. Write a program to print following output

  ******************************* 
  *                             *
  *                             *  
  *                             *
  *******************************
  

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int i,j;
  	clrscr();
  	for(i=1;i<=80;i++)
  		printf("*");
  	for(i=2;i<=23;i++)
  	{
  		printf("*");
  		for(j=2;j<=79;j++)
  			printf(" ");
  		printf("*");
  	}
  	for(i=1;i<=80;i++)
  		printf("*");
  
  	getch();
  
  }
  
  
  

• 056. Write a program to print following output

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
          int i, j;
          clrscr();
          printf("╔");
          for(i=2;i<=79;i++)
                  printf("═");
          printf("╗");
          for(i=2;i<=24;i++)
          {
                  printf("║");
                  for(j=2;j<=79;j++)
                          printf(" ");
                  printf("║");
          }
          printf("╚");
          for(i=2;i<=79;i++)
                  printf("═");
          printf("╝");
   
          getch();
  }
  

• 057. Write a program to accept a single value interger from user and print that integer in words in C language

  #include<stdio.h>
  #include<conio.h>  
  main()
  {
  	int n;
  	clrscr();
  	printf("Enter number...");
  	scanf("%1d",&n);  //%1d to scan single integer
  	switch(n)
  	{
  		case 0 : printf("Zero");break;
  		case 1 : printf("One");break;
  		case 2 : printf("Two");break;
  		case 3 : printf("Three");break;
  		case 4 : printf("Four");break;
  		case 5 : printf("Five");break;
  		case 6 : printf("Six");break;
  		case 7 : printf("Seven ");break;
  		case 8 : printf("Eigth ");break;
  		case 9 : printf("Nine ");break;
  	}
  	getch();
  }