Prac1.c

#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <ctype.h>
void main()
{
    int i, key;
    char text[100], c;
    printf("Enter the plain text : ");
    gets(text);
    printf("Enter Key : ");
    scanf("%d", &key);

    for (i = 0; text[i] != '\0'; ++i)
    {
        c = text[i];
        if (c >= 'a' && c <= 'z')
        {
            c = c + key;
            if (c > 'z')
            {
                c = c - 'z' + 'a' - 1;
            }
            text[i] = c;
        }
        else if (c >= 'A' && c <= 'Z')
        {
            c = c + key;
            if (c > 'Z')
            {
                c = c - 'Z' + 'A' - 1;
            }

            text[i] = c;
        }
    }
    printf("Encrypted Message : %s", text);
}