Monoalphabetic cipher encryption-decryption.

#include<stdio.h>

#include<conio.h>

#include<string.h>

void main()

{

            int i,j,pt,a3,a4,a;

            char a1[50],s1[10],a2[50],s2[50];

            clrscr();

            printf("Enter 0 for capital or 1 for Small latters\n");

            printf("Enter ; at the end of the plaintext\n");

            scanf("%d",&a);

            switch(a)

            {

             case 0:

             {

                        for(i=0;i<26;i++)

                        {

                                    a1[i]=i+65;

                                    printf("%c",a1[i]);

                        }

            printf("\nEnter values for each charater\n");

                        for(i=0;i<26;i++)

                        {

                                    cscanf("%c",&a2[i]);

                        }

             printf("\nEnter the plain text\n");

                        for(i=0;i<100;i++)

                        {

                                    cscanf("%c",&s1[i]);

                                    if(s1[i]==';')

                                         {     s1[i]='\0';

                                                break; }

                        }

            a3=strlen(s1);

            printf("\nThe cyfer text is:");

            for(i=0;i<a3;i++)

                        {for(j=0;j<26;j++)

                                    {       if(s1[i]==' ')

                                                  { printf(" ");}

                                           else if(s1[i]==a1[j])

                                                {

                                                    printf("%c",a2[j]);

                                                }

                                    }

                        }

                        break;   }

              case 1:

              {

                        for(i=0;i<26;i++)

                        {

                                    a1[i]=i+97;

                                    printf("%c",a1[i]);

                        }

                        printf("\nEnter values for each charater\n");

                        for(i=0;i<26;i++)

                        {

                                    cscanf("%c",&a2[i]);

                        }

                         printf("\nEnter the plain text\n");

                         for(i=0;i<26;i++)

                        {

                                    cscanf("%c",&s2[i]);

                                    if(s2[i]==';')

                                         {     s2[i]='\0';

                                                break; }

                        }

                        a4=strlen(s2);

                        printf("\nThe cyfer text is:");

                        for(i=0;i<a4;i++)

                                    {          for(j=0;j<26;j++)

                                           if(s2[i]==' ')

                                                { printf(" ");}

                                           else           {

                                                            if(s2[i]==a1[j])

                                                            {

                                                            printf("%c",a2[j]);

                                                            }

                                                }

                                    }

                }

               }

getch();

}