Lab: Pointer with Strings

1. Program to Input a String and Print It Using a Pointer

#include <stdio.h>

int main() {
  char str[100]; // Declare a character array to store the string
  char *ptr = str; // Pointer to the first character of the string

  // Input the string
  printf("Enter a string: ");
  scanf("%s", str); // Use scanf to read the string

  // Print the string using a pointer
  printf("The string is: ");
  while (*ptr != '\0') {
    putchar(*ptr); // Print each character until null terminator
    ptr++;     // Move to the next character
  }
  printf("\n");

  return 0;
}

2. Program to Count the Number of Vowels and Consonants in a String Using Pointers

#include <stdio.h>
#include <ctype.h>

int main() {
  char str[100]; // Declare a character array to store the string
  char *ptr = str; // Pointer to the first character of the string
  int vowels = 0, consonants = 0;

  // Input the string
  printf("Enter a string: ");
  scanf("%s", str); // Use scanf to read the string

  // Count vowels and consonants
  while (*ptr != '\0') {
    char ch = tolower(*ptr); // Convert to lowercase for comparison
    if (ch >= 'a' && ch <= 'z') { // Check if the character is an alphabet
      if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
        vowels++; // Count vowels
      } else {
        consonants++; // Count consonants
      }
    }
    ptr++; // Move to the next character
  }

  // Print the results
  printf("Number of vowels: %d\n", vowels);
  printf("Number of consonants: %d\n", consonants);

  return 0;
}

3. Program to Reverse a String Using a Pointer

#include <stdio.h>
#include <string.h>

int main() {
  char str[100]; // Declare a character array to store the string
  char *ptr = str; // Pointer to the first character of the string
  int len, i;

  // Input the string
  printf("Enter a string: ");
  scanf("%s", str); // Use scanf to read the string

  // Get the length of the string
  len = strlen(str);

  // Reverse the string using pointer
  printf("The reversed string is: ");
  for (i = len - 1; i >= 0; i--) {
    putchar(*(ptr + i)); // Print each character from the end
  }
  printf("\n");

  return 0;
}

4. Program to Compare Two Strings Using Pointers

#include <stdio.h>

int main() {
  char str1[100], str2[100]; 
  char *ptr1 = str1;     
  char *ptr2 = str2;     

  printf("Enter first string: ");
  scanf("%s", str1); // Read first string
  printf("Enter second string: ");
  scanf("%s", str2); // Read second string

  // Compare strings using pointers
  while (*ptr1 && (*ptr1 == *ptr2)) {
    ptr1++;
    ptr2++;
  }

  // Check the result of the comparison
  if (*ptr1 == *ptr2) {
    printf("The strings are equal.\n");
  } else {
    printf("The strings are not equal.\n");
  }

  return 0;
}

5. Program to Concatenate Two Strings Using Pointers

#include <stdio.h>

int main() {
  char str1[100], str2[100]; 
  char *ptr1 = str1;     
  char *ptr2 = str2;     
  char *ptr;         

  printf("Enter first string: ");
  scanf("%s", str1); 
  printf("Enter second string: ");
  scanf("%s", str2); 

  // Concatenate the strings using pointers
  ptr = str1; 
  while (*ptr) { 
    ptr++;
  }
  while (*ptr2) { 
    *ptr = *ptr2;
    ptr++;
    ptr2++;
  }
  *ptr = '\0'; // Null-terminate the concatenated string

  // Print the concatenated string
  printf("Concatenated string: %s\n", str1);

  return 0;
}