I am writing a program that can duplicate a binary file.
However, the new file will hav extra byte (0xFF) at the end of new file. For example, original file (123.bin) contains 11 Bytes, the generated file (abc.bin) is 12 Bytes, because an extra 0xFF appended at the end of it. How to get rid of it?

123.bin: 6162631198F5BB77660061
abc.bin: 6162631198F5BB77660061FF


*******source code***************
#include <stdio.h>
#include <stdlib.h>

FILE *inFp;
FILE *outFp;

void main() {
    char inFilename[12];
    char outFilename[12];

    int inChar;

    printf("What is the name of the file you want to back up? ");
    gets(inFilename);

    printf("What is the name of the file ");
    printf("you want to copy %s to? ", inFilename);
    gets(outFilename);

    if ((inFp = fopen(inFilename, "rb")) ==NULL) {
        printf("\n\n*** %s does not exist ***\n", inFilename);
        exit(0);
    }

    if ((outFp = fopen(outFilename, "wb")) == NULL) {
        printf("\n\n*** Error opening %s ***\n", outFilename);
        exit(0);
    }

    printf("\nCopying...\n");

    while (!feof(inFp)) {
        inChar = getc(inFp);
        putc(inChar, outFp);
    }

    printf("\nThe files are copied.\n");

    fclose(inFp);
    fclose(outFp);
}

That is true. I had this problem too.
And there is an other problem,
let's say you have the file1 and copy the contents to file2.
The size will be, 11 and 12 bytes respectively.
Now, if you copy file2 to file1, the sizes will be 12 and 13 bytes and so on.....
Maybe garbage in memory!
I'm working on it!

Here's a suggestion: whenever you get a result you don't understand, use printf() to troubleshoot.

For example, use something like
after the line that reads a byte from the file.

If this doesn't tell you something (that is, if you don't understand,
what it tells you) get back to us.


printf() is your friend.


Regards,

Dave

As Dave said, printf() is better solution.

   printf("\nCopying...\n");

    while (!feof(inFp)) {
        inChar = getc(inFp);
        printf("\nThe %i item of file1 : <%02X>\n",i, inChar);

        putc(inChar, outFp);
        printf("The %i item of file2 : <%02X>\n",i, inChar);*/
        i++;
    }

But the problem exists. If you trace the chars with this source code, by making file1 empty, you will see, by copying to file2, that there is an <FFFF> Try it!