vtudeveloper ->> POP Lab Manual - String Operations Program

Program 9

Write functions to implement string operations such as compare, concatenate, and find string length. Use the parameter passing techniques. This program demonstrates custom implementation of standard string library functions and showcases different parameter passing methods in C programming.

String Operations Concepts:

strlen() - Counts characters until null terminator '\0'

strcmp() - Compares ASCII values character by character

strcat() - Appends second string to first string

Parameter Passing: Arrays passed by reference

Algorithm

String Length Function: Traverse string until '\0' and count characters
String Compare Function: Compare characters one by one, return ASCII difference
String Concatenate Function: Find end of first string, append second string
Input Strings: Read two strings from user using gets() function
Display Menu: Show options for length, compare, and concatenate operations
User Choice: Read user's choice for which operation to perform
Execute Operation: Call appropriate function based on user choice
Display Results: Show the result of the selected string operation

Flowchart

START

→

Input Strings

→

Display Menu

→

Read Choice

→

Switch Case

→

Call Function

→

Display Result

→

STOP

Code

#include <stdio.h>


// Function to find length of string
int my_strlen(char str[]) {
    int len = 0;
    while (str[len] != '\0') {
        len++;
    }
    return len;
}

// Function to compare two strings
int my_strcmp(char str1[], char str2[]) {
    int i = 0;
    while (str1[i] != '\0' && str2[i] != '\0') {
        if (str1[i] != str2[i])
            return str1[i] - str2[i];
        i++;
    }
    return str1[i] - str2[i];
}

// Function to concatenate two strings
void my_strcat(char str1[], char str2[]) {
    int i = 0, j = 0;
    // Find end of str1
    while (str1[i] != '\0')
        i++;
    // Append str2
    while (str2[j] != '\0') {
        str1[i] = str2[j];
        i++;
        j++;
    }
    str1[i] = '\0'; // Null terminate
}

int main() {
    char str1[100], str2[100];
    int choice;

    printf("Enter first string: ");
    gets(str1);  // using gets for simplicity (unsafe in practice)
    printf("Enter second string: ");
    gets(str2);

    printf("\nChoose Operation:\n");
    printf("1. Find Length\n");
    printf("2. Compare Strings\n");
    printf("3. Concatenate Strings\n");
    printf("Enter choice: ");
    scanf("%d", &choice);

    switch (choice) {
        case 1:
            printf("Length of first string = %d\n", my_strlen(str1));
            printf("Length of second string = %d\n", my_strlen(str2));
            break;
        case 2: {
            int cmp = my_strcmp(str1, str2);
            if (cmp == 0)
                printf("Strings are equal\n");
            else if (cmp > 0)
                printf("First string is greater\n");
            else
                printf("Second string is greater\n");
            break;
        }
        case 3:
            my_strcat(str1, str2);
            printf("Concatenated string = %s\n", str1);
            break;
        default:
            printf("Invalid choice\n");
    }

    return 0;
}

Output


// Output 1 - String Length Operation
Enter first string: Hello
Enter second string: World

Choose Operation:
1. Find Length
2. Compare Strings
3. Concatenate Strings
Enter choice: 1
Length of first string = 5
Length of second string = 5

// Output 2 - String Comparison (Equal strings)
Enter first string: Programming
Enter second string: Programming

Choose Operation:
1. Find Length
2. Compare Strings
3. Concatenate Strings
Enter choice: 2
Strings are equal

// Output 3 - String Comparison (First string greater)
Enter first string: Zebra
Enter second string: Apple

Choose Operation:
1. Find Length
2. Compare Strings
3. Concatenate Strings
Enter choice: 2
First string is greater

// Output 4 - String Comparison (Second string greater)
Enter first string: Apple
Enter second string: Zebra

Choose Operation:
1. Find Length
2. Compare Strings
3. Concatenate Strings
Enter choice: 2
Second string is greater

// Output 5 - String Concatenation
Enter first string: Hello
Enter second string: World

Choose Operation:
1. Find Length
2. Compare Strings
3. Concatenate Strings
Enter choice: 3
Concatenated string = HelloWorld

// Output 6 - String Concatenation with spaces
Enter first string: Good
Enter second string:  Morning

Choose Operation:
1. Find Length
2. Compare Strings
3. Concatenate Strings
Enter choice: 3
Concatenated string = Good Morning

// Output 7 - Invalid choice handling
Enter first string: Test
Enter second string: Case

Choose Operation:
1. Find Length
2. Compare Strings
3. Concatenate Strings
Enter choice: 5
Invalid choice