For loop

what does this do..?

Q1? for(;;);
Q2? for(p(a);p(b);p(c););

Q1: endless loop.

Q2: How about you try describing what you think it does and we'll correct you. That's ultimately a better way to learn.

My apologies Walt; somewhat unfair - you only answered the first question. I did not however down-rep you in my response if that is any consolation.

A for statement comprises four parts:

1. 1 Initial expression,
2. 2 loop condition expression,
3. 3 loop body
4. 4 iteration expression

And operates thus:

do 1 then while 2 do 3 then 4

Any of 1,2,3 or 4 may be empty (or null) statements. A null statement is just a semi-colon on its own.

An expression is implicitly "true" is it is non-zero.

That is all you need to know to work out the answer to both.