Nested Loops in C Programming

Experiment 5: Nested Loops in C

Objectives

• Introduction to nested loops.

Theory

• This lab explores nested loop structures in C programming.

• Task 1: Print prime numbers between two user-given integers.

  • Outer loop: for loop.

  • Inner loop: while loop (divisibility check).

  • Prime number: No divisors other than 1 and itself.

• Task 2: Pattern printing using user-defined row input.

  • Pattern 1: Left-aligned triangle of stars (nested for loops).

  • Pattern 2: Alphabet-based pattern (nested for loops).

    • Left part: grows from 'a'.

    • Right part: repeats the last character, aligned with spacing.

Codes and Outputs

Problem 1: Prime Numbers

• Objective: Print prime numbers between two given integers using 'for' and 'while' loops.

• Code snippet (C):

  #include <stdio.h>
  
  int main() {
      int start, end;
      printf("Enter the starting number:  ");
      scanf("%d", &start);
      printf("Enter the ending number:  ");
      scanf("%d", &end);
      for (int num = start; num <= end; num++) {
          if (num < 2)
              continue;
          int i = 2;
          int isPrime = 1;
          while (i < num) {
              if (num % i == 0) {
                  isPrime = 0;
                  break;
              }
              i++;
          }
          if (isPrime) {
              printf("%d ", num);
          }
      }
      printf("\n");
      return 0;
  }
  

• Example:

  • Input: start = 1, end = 8

  • Output: 2 3 5 7

Problem 2: Pattern Printing

Pattern [i]: Triangle of Stars

• Objective: Print a left-aligned triangle of stars.

• Code snippet (C):

  #include <stdio.h>
  
  int main() {
      int i, j;
      for(i = 1; i <= 5; i++) {
          for(j = 1; j <= i; j++) {
              printf("* ");
          }
          printf("\n");
      }
      return 0;
  }
  

• Output:

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

Pattern [ii]: Alphabet Pattern

• Objective: Print an alphabet-based pattern.

• Code snippet (C):

  #include <stdio.h>
  
  int main() {
      int i, j;
      int n = 5;
      for(i = 1; i <= n; i++) {
          for(j = 0; j < i; j++) {
              printf("%c", 'a' + j);
          }
          switch(i) {
              case 1: printf("  "); break;
              case 2: printf("  ");  break;
              case 3: printf("  ");  break;
              case 4: printf("  "); break;
              case 5: printf("  ");  break;
          }
          char ch = 'a' + i - 1;
          for(j = 0; j < i; j++) {
              printf("%c", ch);
          }
          printf("\n");
      }
      return 0;
  }
  

• Output:

a a

ab bb

abc ccc

abcd dddd

abcde eeeee

Discussion

• Nested loops and conditional logic were practiced.

• Prime number identification: for and while loops.

• Pattern printing: star triangle and alphabet patterns.

• Reinforced control structures and output formatting.