More rewording, mention ?do.

forth.html.markdown

@@ -67,11 +67,10 @@ Forth, but most of what is written here should work elsewhere.
 
 \ ------------------------------ Creating Words --------------------------------
 
-\ Quite often one will want to write their own words.
+\ The `:` word sets Forth into compile mode until it sees the `;` word.
 : square ( n -- n ) dup * ;    \ ok
 
-\ The `:` word sets Forth into compile mode until it sees the `;` word.
-
+\ We can view what a word does too:
 see square     \ dup * ; ok
 
 \ -------------------------------- Conditionals --------------------------------
@@ -101,19 +100,22 @@ myloop
 \ Hello!
 \ Hello! ok
 
-\ `do` expects two numbers on the stack: the end number and the index number.
+\ `do` expects two numbers on the stack: the end number and the start number.
 
 \ We can get the value of the index as we loop with `i`:
 : one-to-12 ( -- ) 12 0 do i . loop ;     \ ok
 one-to-12                                 \ 0 1 2 3 4 5 6 7 8 9 10 11 12 ok
-: squares ( n -- ) 0 do i dup * . loop ;  \ ok
+
+\ `?do` works similarly, except it will skip the loop if the end and start
+\ numbers are equal.
+: squares ( n -- ) 0 ?do i dup * . loop ;  \ ok
 10 squares                                 \ 0 1 4 9 16 25 36 49 64 81 ok
 
 \ Change the "step" with `+loop`:
-: threes ( n n -- ) do i . 3 +loop ;    \ ok
+: threes ( n n -- ) ?do i . 3 +loop ;    \ ok
 15 0 threes                             \ 0 3 6 9 12 ok
 
-\ Finally, while loops with `begin` <stuff to do> <flag> `unil`:
+\ Indefinite loops with `begin` <stuff to do> <flag> `unil`:
 : death ( -- ) begin ." Are we there yet?" 0 until ;    \ ok
 
 \ ---------------------------- Variables and Memory ----------------------------
@@ -195,9 +197,15 @@ myfloatingvar f@ f.       \ 4.4 ok
 \ specifically for that:
 clearstack
 
+\ Clear the screen:
+page
+
 \ Loading Forth files:
 \ s" forthfile.fs" included
 
+\ You can list every word that's in Forth's dictionary (but it's a huge list!):
+\ words
+
 \ Exiting Gforth:
 \ bye