Quick question

[spikestar]

I'm doing some exam revision and I'm stuck at this question. If some one could explain to me how this answer is obtained, it would be much appreciated:

char alpha[] = "abcdefghi";
char ch[80], *pch = &ch[0];

what does the following code print?

strcpy(ch, alpha);
putchar(*pch++);
putchar((*pch)++);
putchar(*++pch);
putchar(++(*pch));
printf("\n%s", ch);

ANSWER:

a
b
c
d

acddefghi

[quzah]

Write out what you think each line does.


Quzah.

[spikestar]

strcpy(ch, alpha);

this line copies the string array alpha to array ch;

putchar(*pch++);

prints the character at ch[0] which is a, and the pch is incremented by +1 and is now pointing to ch[1]

putchar((*pch)++)

prints the character at ch[1] which is a, and the pch is incremented by +1 and is now pointing to ch[2]

Its now at these lines that i get confused:

putchar(*++pch);

this line prints c, but wouldn't it print d since ++ is a prefix. so if pch is pointing to ch[2], wouldnt it increment ch to ch[3] and then print d.

From here I'm lost....

[laserlight]

prints the character at ch[1] which is a, and the pch is incremented by +1 and is now pointing to ch[2]

Notice that the ++ is applied to the result of (*pch), not to pch.

[spikestar]

would any one be able to give me full explanation of the code and how it works? It's quiet frustrating me now ...

[laserlight]

This:

putchar(*pch++);

can be written as:

putchar(*pch);
pch++;

This:

putchar((*pch)++);

can be written as:

putchar(*pch);
(*pch)++;

This:

putchar(*++pch);

can be written as:

++pch;
putchar(*pch);

This:

putchar(++(*pch));

can be written as:

++(*pch);
putchar(*pch);