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;
}