Question

C Program
Type a program in C to encode the message with Caesar's cipher. Your program will receive a text message, and the key value will then generate an encryption text for the given message. 
example:
Enter a message to encrypt: axzd
Enter key: 4
Encrypted message: ebdh

**Make sure your program can check that the given message is not empty AND Your program must include a helper function that accepts the input message and checks that it contains only characters before generating the ciphertext

Answer 1

#include<iostream>  

using namespace std;

int main()

{

char message[100], ch;

int i, key, check=0;

printf("Enter a message to encrypt: ");

do{

gets(message);

check=helper_fun(message);

} while (check== 0 || message.empty());

printf("Enter key: ");

scanf("%d", &key);

for(i = 0; message[i] != '\0'; ++i){

ch = message[i];

if(ch >= 'a' && ch <= 'z'){

ch = ch + key;

if(ch > 'z'){

ch = ch - 'z' + 'a' - 1;

}

message[i] = ch;

}

else if(ch >= 'A' && ch <= 'Z'){

ch = ch + key;

if(ch > 'Z'){

ch = ch - 'Z' + 'A' - 1;

}

message[i] = ch;

}

}

printf("Encrypted message: %s", message);

return 0;

}

int helper_fun(char s[100] )

{

int i,F=0;

For(i=0;i<s.length();i++)

{

If(isalpha(s[i])!=0)

F=1;

}

If(F==0)

return 1;

else {

cout<<”contains characters other than alplabets or letters”;

return 0;

}

}

Please make changes according to your ide.