What exactly is 'do-events' for?

I have written a few REBOL2 applications using VIEW, with success. I usually make a main window, with buttons that do things including sometimes viewing other windows. It all seems to work fine. When I look at sample programs, on rebol.org for example, I sometimes see programs that display a window and then "do-events." I don't understand what "do-events" does for me since my programs seem to work fine without it. Thank you.

It's usually used together with view/new, in cases where you need the GUI layout to exist before showing it, usually to perform some calculation before the event loop begins (before the system starts watching for user events). Do-events just starts the event loop (so you can also use it to restart a GUI that's stopped do to an error). In this example, I wanted the cards to be arranged before the GUI layout is shown. In order to do that, the GUI needs to exist, so I used view/new, then ran the arrange-cards functions, then do-events: R E B O L [title: "Playing Card Framework - Freecell"] flash "Downloading card images..." do load-thru http://www.re-bol.com/playing-cards.r unview random/seed now loop 156 [ pos1: pick cards rnd1: (random 52) * 5 pos2: pick cards rnd2: (random 52) * 5 poke cards rnd1 pos2 poke cards rnd2 pos1 ] movestyle: [ engage: func [face action event] [ if action = 'down [ start-coord: face/offset face/data: event/offset remove find face/parent-face/pane face append face/parent-face/pane face ] if find [over away] action [ unrounded-pos: (face/offset + event/offset - face/data) snap-to-x: (round/to first unrounded-pos 80) + 20 snap-to-y: (round/to second unrounded-pos 20) + 20 face/offset: (as-pair snap-to-x snap-to-y) ] if action = 'up [ if any [ (find cards face/offset) (face/offset/2 < 20) ] [ if (face/offset/2 < 398) [face/offset: start-coord] ] replace cards start-coord face/offset arrange-cards ] show face ] ] positions: does [ temp: copy [] foreach item cards [if ((type? item) = pair!) [append temp item]] return sort temp ] arrange-cards: does [ foreach position positions [ foreach card system/view/screen-face/pane/1/pane [ if (card/offset = position) and (position/2 < 398) [ remove find system/view/screen-face/pane/1/pane card append system/view/screen-face/pane/1/pane card ] ] ] show system/view/screen-face/pane/1/pane ] gui: [size 670x510 backdrop 0.150.0 across ] foreach [card label num color pos] cards [ append gui compose [ at (pos) image load to-binary decompress (card) feel movestyle ] ] box-pos: 18x398 loop 4 [ append gui compose [ at (box-pos) box green 72x2 at (box-pos) box green 2x97 at (box-pos + 320x0) box white 72x2 at (box-pos + 320x0) box white 2x97 ] box-pos: box-pos + 80x0 ] view/new center-face layout gui arrange-cards do-events You'll see a similar procedure in this image capture code: avicap32.dll: load/library %avicap32.dll user32.dll: load/library %user32.dll find-window-by-class: make routine! [ ClassName [string!] WindowName [integer!] return: [integer!] ] user32.dll "FindWindowA" sendmessage: make routine! [ hWnd [integer!] val1 [integer!] val2 [integer!] val3 [integer!] return: [integer!] ] user32.dll "SendMessageA" sendmessage-file: make routine! [ hWnd [integer!] val1 [integer!] val2 [integer!] val3 [string!] return: [integer!] ] user32.dll "SendMessageA" cap: make routine! [ cap [string!] child-val1 [integer!] val2 [integer!] val3 [integer!] width [integer!] height [integer!] handle [integer!] val4 [integer!] return: [integer!] ] avicap32.dll "capCreateCaptureWindowA" view/new center-face layout/tight [ image 320x240 across btn "Take Snapshot" [ sendmessage cap-result 1085 0 0 sendmessage-file cap-result 1049 0 "scrshot.bmp" browse %scrshot.bmp ] btn "Exit" [ sendmessage cap-result 1205 0 0 sendmessage cap-result 1035 0 0 free user32.dll quit ] ] hwnd: find-window-by-class "REBOLWind" 0 cap-result: cap "cap" 1342177280 0 0 320 240 hwnd 0 sendmessage cap-result 1034 0 0 sendmessage cap-result 1077 1 0 sendmessage cap-result 1075 1 0 sendmessage cap-result 1074 1 0 sendmessage cap-result 1076 1 0 do-events