split into two c files and one header file.

[jihyungkim94]

For this part, I want you to revisit your Caesar encryption code from assignment 3 and modify it
so it contains at least two .c files: a driver containing the main function and a support file
containing a function that runs your Caesar encryption code. These files will be linked by a
header file (.h file).
The main function shall prompt the user to enter a string to encrypt and an encryption key to
offset the string values. These values are then passed the caesarEncrypt function, which encrypts
the string and prints out the value, and returns the number of characters in the string as check for
the user. A suggested caesarEncrypt prototype is int caesarEncrypt(const char inputString[], int
key);
The file caesar.h contains the function prototype for your Caesar encryption function and any
other functions located in caesar.c. In caesar.c and main.c, link the file together with common
header #include “caesar.h”
This header file with give main.c the definitions of the prototypes in declared in caesar.c.
Your header will use macros to ensure that files are only included once.

#include <stdio.h>


#define MAX 80
#define UPPER_ENCRYPT ((ch - 'A') + offset) % 26 + 'A'
#define LOWER_ENCRYPT ((ch - 'a') + offset) % 26 + 'a'
int len, offset;
char message[MAX], c;


int main(void)
{


        printf("Enter message to be encrypted: ");
        for (len = 0; (c = getchar()) != '\n'; len++) {
                message[len] = c;
        }


        printf("Enter shift amount (1-25): ");
        scanf("%d", &offset);


        printf("Encrypted message: ");
        for (int i = 0; i < len; i++) {
                char ch = message[i];


                if (message[i] >= 'a' && message[i] <= 'z') {
                        ch = LOWER_ENCRYPT;
                } else if (message[i] >= 'A' && message[i] <= 'Z') {
                        ch = UPPER_ENCRYPT;
                }
                printf("%c", ch);
        }
        printf("\n");


        return 0;
}

Help me please.

[stahta01]

Step 1: Create the function caesarEncrypt in the same file as the main function.
But, create it after the main function.

Step 2: Split into three files.

Tim S.

[jihyungkim94]

Well I have no idea how to handle this. Can you do more specific?

[stahta01]

Functions in C - Cprogramming.com

[Hodor]

I find these encryption assignments fascinating. They're very common and nearly invariably the students implementing them do stuff like

if (message[i] >= 'a' && message[i] <= 'z') {

which is implementation dependent. I guess it's entrenched now

[ordak]

I find these encryption assignments fascinating. They're very common and nearly invariably the students implementing them do stuff like

if (message[i] >= 'a' && message[i] <= 'z') {

which is implementation dependent. I guess it's entrenched now

An interesting standard header ctype.h
For instance:

if( isalpha(ch) && islower(ch) )