[ColorForth] More newbie questions

[Leslie Snively <les@xxxxxxxxxxxxxx>]

I've finally been able to start learning/experimenting with colorForth 
again and it's taken me only a few minutes to run into another beginner 
question:  How does "if" work?  Yes, I've read the definition that it 
jumps to then if the zero flag is set.  But how does one set the zero 
flag?  I would assume by the number zero being the top item on the 
stack, but that doesn't seem to do it.  For example, using the following 
word:

[R]iftest [G] if 1 ; then 0 ;

I would expect "4 iftest" to leave a 1 on the stack and "0 iftest" to 
leave a 0 on the stack.  However, it actually returns "4 0" and "0 0".  
It's clear that I'm missing something simple.  It seems that "if" does 
not consume the value on the stack, which would make sense if it's 
actually using a zero flag somewhere as the switch.  All guidance will 
be appreciated.

Also, what does the word "?" do?  The documentation isn't clear to me 
for this word either.

Thanks,
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