Stuck With Creating Encryption Program

[Propheciah]

Hello everyone. I have been given an assignment that I've been struggling with.

The idea is, the user needs to input a four digit number. If the number input only has 1-3 digits, the program is to assume that the empty spaces in front of those numbers are 0.

If it has 5+ digits, it will return an error message.

Then, each digit of the number is replaced by (the sum of the digit with the number 7) modulo 10.

The three functions I am required to use are:

int readNumber(); //function to read a four-digit number
int encrypt(int data); //function to encrypt data
int decrypt(int data); //function to decrypt data

It would be extremely helpful for someone to look over what I have so far and provide some input on how to move forward.

I have a decent amount complete, but I keep getting "too few arguments to function" errors for my encrypt and decrypt functions.



Example:

When the user selects to Encode or decode a number:

Please select one of the following:
1. Encode a number.
2. Decode a number.

Enter choice: 1

Enter the four digit number: 7645

The encrypted number is: 2134

#include <stdio.h>
#include <iostream>
#include <string.h>

using namespace std;

int encrypt(int Num1, int Num2, int Num3, int Num4);
int decrypt(int Num1, int Num2, int Num3, int Num4);
int readNumber();
char choice;


int main()
{
	cout << endl; 
	
	cout << "Please select one of the following: " << endl;
	
	cout << "1. Encrypt a number " << endl;
	
	cout << "2. Decrypt a number " << endl; 
	
	cout << endl;
	
	cout << "Enter choice: ";
	
	cin >> choice; 
	
	cout << endl;
	
	
	if (choice == '1')
	{
		readNumber();
		encrypt();
	}
	
	
	else if (choice == '2')
	{
		readNumber();
		decrypt();
	}
	
	
	else 
	{
		cout << "Invalid choice. Try again. " << endl;
		return main();
	}
}

int readNumber()
{
	int number;
	int Num1,Num2,Num3,Num4;
	
	cout << "Enter the four digit number: ";
	
	cin >> number;
	
	cout << endl;
	
	Num1 = number / 1000;
	Num2 = number / 100 - 10*Num1;
	Num4 = number%10;
	Num3 = (number%100 - Num4) / 10;
	
    return 0;
}

int encrypt(int Num1, int Num2, int Num3, int Num4)
{
	cout << "The encrypted number is: "
			 << (Num4 + 7)%10
			 << (Num3 + 7)%10
			 << (Num2 + 7)%10
			 << (Num1 + 7)%10
			 << endl; 
			 return 0;
}
	
int decrypt(int Num1, int Num2, int Num3, int Num4)
{
	cout << "The decrypted number is: "
			 << (Num1 + 3)%10
			 << (Num2 + 3)%10
			 << (Num3 + 3)%10
			 << (Num4 + 3)%10
			 << endl; 
			 return 0;
}

[coder777]

On line 35/42 you need to pass four parameter but you provide none.
To solve this I suggest that you pass the values by reference to readNumber() and then to the appropriate function (by value):

#include <stdio.h>
#include <iostream>
#include <string.h>

using namespace std;

int encrypt(int Num1, int Num2, int Num3, int Num4);
int decrypt(int Num1, int Num2, int Num3, int Num4);
int readNumber(int &Num1, int &Num2, int &Num3, int &Num4);
char choice;


int main()
{
...
	
	if (choice == '1')
	{
int Num1, Num2, Num3, Num4;
		readNumber(Num1, Num2, Num3, Num4);
		encrypt(Num1, Num2, Num3, Num4);
	}

...
}

int readNumber(int &Num1, int &Num2, int &Num3, int &Num4)
{
	int number;
	int Num1,Num2,Num3,Num4;
	
	cout << "Enter the four digit number: ";
..
}

http://www.learncpp.com/cpp-tutorial/73-passing-arguments-by-reference/