How does it work?

Got this code to analyze.

Code:

int i,m,*g_p;
int g[10]={1,5,3,4,0,22,8,0,-53,7};
main()
{
	m=0;
	g_p=g;
	for (i=0;i<10;g_p++,m++,i++)
	{
			printf ("first loop: m=%d  *g_p=%d\n",m, *g_p);
			printf ("\n");
		for (;*g_p;g_p++,i++);
			printf ("second loop: m=%d  *g_p=%d\n",m, *g_p);
			printf ("\n");
	}
	printf ("end of program: m=%d  *g_p=%d\n",m, *g_p);
}

Figured out that it calculates the numbers of series, delimited by 0. I don’t understand:
1. How does the pointer *g_p “jump” directly to 22 & then to -53.
2. Why does it get the value of 0?
3. What means the

Code:

*g_p

in

Code:

    for (;*g_p;g_p++,i++);

output:
first loop: m=0 *g_p=1

second loop: m=0 *g_p=0

first loop: m=1 *g_p=22

second loop: m=1 *g_p=0

first loop: m=2 *g_p=-53

second loop: m=2 *g_p=0

end of program: m=3 *g_p=0

The behaviour of the program is undefined.

It might help you understand the code if you change:

Code:

		for (;*g_p;g_p++,i++);

to:

Code:

		for (;*g_p;g_p++,i++) /* Do nothing */;

and analyse what this loop is doing.

Did that with out further understanding.

Would it help you if I said:

Code:

for (;*g_p;g_p++,i++);

is equivalent to:

Code:

while (*g_p != 0)
{
    g_p++;
    i++;
}

Try running through the code step by step.

the style of that code looks ancient.

OK now all understood!