Simple Cipher Program

**PunchOut** · 11-22-2008

Hello everyone, i am in the beginning stages of creating my own caesar cipher and i am running into trouble with my cipher array.

If you run the program below and just input something simple like "my name is john doe" . "array" returns what it is supposed to, but "cipher" returns the encrypted message plus some other garbage as shown below:
"p|qdphlvu|dq�Rп��ȁ�Rп�".

What can i do to correct this?

here is the code:

Code:

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

#define MAX 100

main()
{
	char array[MAX], cipher[MAX];
	int i, x, c;
	i = x = 0;
	while((c=getchar()) != '\n')
	{
		array[i] = c;
		cipher[x] = (int) c + 3;
		x++;
		i++;
	}
	printf("%s\n", array);
	printf("%s\n", cipher);
}

**Tux0r** · 11-22-2008

You have to init your char arrays from garbage to clean empty fills of zeros

Code:

#include <stdio.h>

int main() {
	char array[100]={0}, cipher[100]={0};

	int c;
	while((c=getchar()) != '\n') {
		static int x=0, i=0;

		array[i++]=(char)c;
		cipher[x++]=(char)(c+3);
	}

	printf("&#37;s\n",cipher);

	return 0;
}

**PunchOut** · 11-22-2008

wow, that was quick!

thanks for the insight, much appreciated

**Tux0r** · 11-22-2008

Well the best way is to just init your char array to 0 as I did.
edit: np

**MeTh0Dz** · 11-22-2008

It's not really necessary to initiate the arrays to zero.

You just need to NUL terminate the string.

**PunchOut** · 11-22-2008

Originally Posted by MeTh0Dz

It's not really necessary to initiate the arrays to zero.

You just need to NUL terminate the string.

is this what you mean?

cipher[x++] = '\0'

**Tux0r** · 11-22-2008

Originally Posted by MeTh0Dz

It's not really necessary to initiate the arrays to zero.

You just need to NUL terminate the string.

It might not be necessary but if you do init char arrays, there is no need to worry about their usage later when it comes to this kind of problem.

Originally Posted by PunchOut

is this what you mean?

cipher[x++] = '\0'

This is the way he/she proposed:

Code:

#include <stdio.h>

int main() {
	char array[100], cipher[100];
	int c=0, x=0, y=0;

	while((c=getchar()) != '\n') {
		array[x++]=(char)c;
		cipher[y++]=(char)(c+3);
	}

	array[x]=0;
	cipher[y]=0;

	printf("&#37;s\n",cipher);

	return 0;
}

**vart** · 11-22-2008

you need to add the size limit check - to prevent writing beyong bounds of the arrays

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