changing letters by rotating them around?

i'm suppose to use this code to rotate characters from this input file (blah_input.txt)....

Now is the time for all good persons to come to the aid of their
party. Hello world! 1234 !@#$

to this output file(blah_output.txt)...

Abj vf gur gvzr sbe nyy tbbq crefbaf gb pbzr gb gur nvq bs gurve
cnegl. Uryyb jbeyq! 1234 !@#$

instead i just end up with chinese characters for some reason....help please.

Code:

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

int (encode(int input_char));
int main(void)
{
        FILE * in;
        FILE * out;
        char input_char;
        int char_total = 0;

        in = fopen("blah_input.txt", "r");
        if(in == NULL)
        {
                printf("Sorry, unable to open input file.\n");
                exit(1);
        }

        out = fopen("blah_output.txt", "w");
        if (out == NULL)
        {
                printf("Sorry, unable to open output file.\n");
                exit(1);
        }

        while ((input_char = fgetc(in)) != EOF)
        {
                fputc(encode(input_char), out);
                char_total = char_total + 1;
        }

        fprintf(out, "\n%d characters", char_total);


        fclose(in);
        fclose(out);

        return 0;
}
int encode(int input_char)

        {
                if (('a' <= input_char) && (input_char <= 'm'))
                {
                        return input_char + 13;
                }

                else if (('n' <= input_char) && (input_char <= 'z'))
                {
                        return input_char - 13;
                }

                if (('A' <= input_char) && (input_char <= 'M'))
                {
                        return input_char + 13;
                }

                else if (('N' <= input_char) && (input_char <= 'Z'))
                {
                        return input_char - 13;
                }
        }

---

You need to make sure you are changing characters into readable characters, not jarble.

Why don't you have the string.h library included. It would seem like that standard lib would be best. Your while statement is actually going to set that variable. Or am I too much of a noob to read this code correctly?

What platform are you on?

Your encode() function doesn't return anything for characters that aren't alphabetical, so any non-alphabetic characters are going to be replaced with garbage -- the garbage probably contains weird escape sequences which are throwing your terminal into a funky mode.

A non-alphabetic character should just be replaced with itself, so maybe try adding this at the very end of the encode function:

Code:

---

return input_char;

---