Help wanted on some source codes

1.===========================================
/* a.c */
int x;
int y;

void main()
{
f();
printf("%x %x\n", x, y);
}

/* b.c */
double x;

void f()
{
x = -0.0;
}


2.===========================================
/* a.c */
int x = 1;
int y;

void main()
{
f();
printf("%x %x\n", x, y);
}

/* b.c */
double x;

void f()
{
x = -0.0;
}

3.===========================================
/* a.c */
int x;
int y = 1;

void main()
{
f();
printf("%x %x\n", x, y);
}

/* b.c */
double x;

void f()
{
x = -0.0;
}

4.===========================================
/* a.c */
int x = 1;
int y = 1;

void main()
{
f();
printf("%x %x\n", x, y);
}

/* b.c */
double x;

void f()
{
x = -0.0;
}

5.===========================================
/* a.c */
int x = 1;
int y = 1;

void main()
{
f();
printf("%x %x\n", x, y);
}

/* b.c */
double x;

void f()
{
x = -0;
}


Remark=======================================
The above programs from 1 to 5 are all constituted
of two separate files, a.c & b.c, and can be
compiled under gcc.
e.g.
/* Linux */
$ gcc -o test a.c b.c
$ ./test
/* Windows */
C:\gcc -o test.exe a.c b.c
C:\test


Question=======================================
I'm wondering about the strange results generated
by the programs. Please help me. I want to understand
why the results are like that.
By the way, the source codes above are in old K&R style
and will be warned by the gcc, you can change them to
new ISO/ANSI style :-)

Thanks in advance & best regards!

Becker
30-Nov-2005

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