Monoalphabetic Cipher Program

 *PROGRAM*

#include<stdio.h>

#include<string.h>

int main()

{

    char pt[26]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};

    char ct[26]={'Z','Y','X','W','V','U','T','S','R','Q','P','O','N','M','L','K','J','I','H','G','F','E','D','C','B','A'};

    char p[26]={'\0'},c[26]={'\0'},r[26]={'\0'};

    int i,j,choice;

 

    do

    {

    printf("\n 1. Encryption");

printf("\n 2. Decryption");

printf("\n 3. Exit");

printf("\n\nEnter Choice:-");   

    scanf("%d",&choice);

switch(choice)

{

case 1:

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

    scanf("%s",&p);

    

for(i=0;i<strlen(p);i++)

    {

    for(j=0;j<26;j++)

        {

if(pt[j]==p[i])

            {

c[i]=ct[j];

        }

}

}

    printf("\nCipher text is: %s",c);

break;

case 2:

printf("\nEnter the cipher text:");

scanf("%s",&c);

    

for(i=0;i<strlen(c);i++)

    {

    for(j=0;j<26;j++)

    {

    if(ct[j]==c[i])

        {

        r[i]=pt[j];

}

}

    }

    printf("\nPlain text is: %s",r);

break;

case 3: break;

}

}while(choice<3);

return 0;

}

 *OUTPUT*