In this case graphics coordinates are used -- notice the numbers are separated
by semicolons unlike the VDU 28 command.
You can see the graphics window by typing:
GCOL 0,130
CLG
Although graphics are now displayed only within the window, the whole screen
is still used for text. To completely separate text and graphics we must set up
both a graphics and a text window. Create a text window below the graphics
window by typing:
VDU 28,5,31,34,28
Change the background text colour to red:
COLOUR 129
CLS
Type in some MOVE and DRAW commands. The text is displayed within the
text window, and any lines drawn only appear within the graphics window.
After a VDU 26 command the whole screen is used for text and graphics once
again, so return things to normal by typing:
VDU 26
Note that using a MODE command has the same effect as it automatically
destroys all windows.
Printing text at graphics positions
TAB is used to print characters on the screen at any text coordinate. It is
sometimes helpful to position text more accurately on the screen than PRINT
TAB allows, especially if graphics are also used.
In modes in which graphics can be used, text can be printed at graphics
coordinates after a VDU 5 command. This program gives a three dimensional
effect by printing the same message twice and slightly off-setting the second set
of characters which are printed in a different colour:
10 MODE 1
20 PRINTTAB(16,15)"H e l l o"
30 VDU 5
40 GCOL 0,1
50 MOVE 516,540
60 PRINT''H e l l 0"
70 VDU 4
C 26