Q(uick)BASIC Statement: SCREEN

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SCREEN

A graphics statement that sets the specifications for the display screen

Worth knowing

Useful and cross-version information about the programming environments of QBasic and QuickBasic.

Syntax
  • SCREEN mode% [,[colorswitch%] [,[activepage%] [,visualpage%]]]
Description/Parameter(s)
mode% Sets the screen mode. See ⮜ Screen Modes ⮞.
colorswitch% A value (0 or 1) that switches between color and monocolor display (modes 0 and 1 only):
ModeValueAction
00Disables color
0NonzeroEnables color
10Enables color
1NonzeroDisables color
activepage% The screen page that text or graphics output writes to.
visualpage% The screen page that is currently displayed on your screen.
Example
'This example requires a color graphics adapter. SCREEN 1 '320 x 200 graphics LINE (110, 70)-(190, 120), , B LINE (0, 0)-(320, 200), 3, , &HFF00

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Syntax
  • SCREEN [mode][,[colorswitch]][,[apage]][,[vpage]]
Description/Parameter(s)
Argument Description
mode An integer constant or expression indicating the screen mode. See ⮜ Screen Mode Summary ⮞ for a list of the valid mode numbers.
colorswitch Determines whether color is displayed on composite monitors. The colorswitch is a numeric expression in the range 0-255.
  • When it is true (nonzero), color is disabled and only black and white images are displayed.
  • When colorswitch is false (zero), images are in color.
  • The meaning of the colorswitch argument is inverted in screen mode 0.
In screen modes 2 and up, colorswitch is ignored.
apage A numeric expression that is the number of the screen page that text output or graphics commands write to. See ⮜ Adapters and Displays ⮞ for the number of pages available for each graphics adapter.
vpage A numeric expression that is the number of the screen page being displayed.
Example

See any of the following example programs, which use the SCREEN statement:
the ⮜ CIRCLE statement programming example ⮞,
the ⮜ DRAW statement programming example ⮞, or
the ⮜ LINE statement programming example ⮞.

See also:

Syntax
  • SCREEN mode% [, [colorswitch%] [, [activepage%] [,visiblepage%]] ]
Description/Parameter(s)
mode% An integer constant or expression that selects a screen mode for a particular combination of display and adapter.
See ⮜ Screen Mode Summary ⮞ for a list of the valid mode numbers.
colorswitch% An integer expression that switches composite monitor display between color and noncolor (modes 0 and 1 only).
activepage% An integer expression that identifies the screen page that text or graphics output is written to.
visiblepage% An integer expression that identifies the screen page that is displayed.
In OS/2 protected mode, BASIC supports only screen modes 0-2 and does not support the activepage% and visiblepage% arguments. In OS/2 real mode, BASIC supports screen modes 0-4 and 7-13.

Optimization Note

  • If mode% is an expression, rather than a constant, and if you know your program will not use certain screen modes, you can achieve a smaller .EXE file by linking with one or more stub files:
    If not using screen modes:Link to file:
    1 or 2NOCGA.OBJ
    3NOHERC.OBJ
    4NOOGA.OBJ
    7, 8, 9, or 10NOEGA.OBJ
    11, 12, or 13NOVGA.OBJ
  • If you do not need graphics in your custom run-time module (because the programs use screen mode 0 only), you can save 15K by creating the run-time module with NOGRAPH.OBJ.

Syntax Notes

  • See for a list of the valid mode% numbers.
  • The argument colorswitch% is effective only for screen modes 0 and 1 and for composite monitors:
     Screen mode 0Screen mode 1
    To disable color, use...0A non-zero value
    To enable color, use...A non-zero value0
  • See ⮜ Adapters and Displays ⮞ for the valid ranges for apage% and vpage% for each graphics adapter.
  • See ⮜ Attributes and Colors ⮞ for a list of the default color attributes for different screen modes.
Example

This example uses the SCREEN statement to set up a multipage EGA or VGA mode 7 (320x200) display. A help screen is displayed for several seconds, then copied (using the PCOPY statement) to page 2 for later use. A cube is displayed and rotated on the screen. By pressing Shift+F1, the user can again see the help screen, after which the cube display is resumed.

DEFINT A-Z 'Define a macro string to draw a cube and paint its sides. One$ = "BR30 BU25 C1 R54 U45 L54 D45 BE20 P1, 1G20 C2 G20" Two$ = "R54 E20 L54 BD5 P2, 2 U5 C4 G20 U45 E20 D45 BL5 P4, 4" Plot$ = One$ + Two$ 'Initialize values for active page, visual page, help page, and angle 'of rotation. APage% = 0 VPage% = 1 HPage% = 2 Angle% = 0 'Create a HELP screen on the visual page. SCREEN 7, 0, VPage%, VPage% LOCATE 1, 18 PRINT "HELP" LOCATE 5, 1 PRINT "Press 'Alt+F1' keys to see this HELP" PRINT "screen while the cube is rotating" PRINT "around the center of the screen. " PRINT PRINT "After a brief delay, the cube will" PRINT "resume at the next point in it's" PRINT "rotation." PRINT PRINT "Press any other key to exit the" PRINT "program. " 'Put a copy of the help screen in page 2. PCOPY VPage%, HPage% SLEEP 5 DO SCREEN 7, 0, APage%, VPage% 'Clear the active page. CLS 1 'Rotate the cube Angle% degrees. DRAW "TA" + STR$(Angle%) + Plot$ 'Angle% is some multiple of 15 degrees. Angle% = (Angle% + 15) MOD 360 'Drawing is complete. Make the cube visible in its new position 'by swapping the active and visual pages. SWAP APage%, VPage% 'Check the keyboard input. Kbd$ = INKEY$ SELECT CASE Kbd$ 'If Shift+F1 is pressed, show the HELP page. CASE CHR$(0) + CHR$(104) PCOPY HPage%, APage% SLEEP 3 'Do nothing if no key is pressed. CASE "" CASE ELSE EXIT DO END SELECT LOOP END

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