I tried the following program to copy one binary file (a.txt) to another (b.txt). And found that b.txt has one extra char: 0xFF.

What is the reason?

1. source code
==============================
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char** argv)
{
FILE *in, *out;
char ch;

if(argc != 3)
{
printf("Usage:: %s src dest\n", argv[0]);
exit(0);
}

if((in = fopen(argv[1], "rb")) == NULL)
{
printf("Cannot open file %s.", argv[1]);
exit(0);
}

if((out = fopen(argv[2], "wb")) == NULL)
{
printf("Cannot open file %s.", argv[2]);
exit(0);
}

while(!feof(in))
{
fputc(fgetc(in), out);
}

fclose(in);
fclose(out);

return 0;
}

2. a.txt and b.txt viewed in UltraEdit-32 (see picture)
=================================

[此贴子已经被作者于2007-8-23 13:15:28编辑过]

That is a neat solution.

Thanks brother 雨中飞燕.

My understanding for EOF is that the value of EOF is -1:

printf("%d\n", EOF); // outputs -1 on my machine

and when I use

fputc(-1, out); // this writes 0xFF to the output stream

I got the 0xFF since 255 = 256-1.

very good analysis, brother.

I do have a copy of Stroustrup's C++ and K and R's C --- but I have no patience to read them all.