char test;

Code:

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

int checkline(char *line)
{
	int len = strlen(line);
	int i;

	if (line[len-1] == '\n')
		line[--len] = '\0';
	for (i=0; i<len; i++)
		if (!isalpha(line[i]) && !isdigit(line[i]) &&
			line[i] != '.' && line[i] != ',' && line[i] != '?' && line[i] != '!')
			return -1;
	return 0;
}

void encode(char *line)
{
	int len = strlen(line);
	int i;

	for (i=0; i<len; i++)
		line[i] += 5;
}

int main(int argc, char* argv[])
{
	char line[82];
	for (;;)
	{
		if (fgets(line, 82, stdin) == NULL)
			break;
		if (checkline(line))
			printf("Fehlerhafte Eingabe\n");
		else
		{
			printf("%s\n", line);
			encode(line);
			printf("%s\n", line);
		}
	}
	return 0;
}