SCREEN (function)
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The SCREEN function returns the ASCII code of a text character or the color attribute at a set text location on the screen.
Syntax
- codeorcolor% = SCREEN (row%, column% [, colorflag%])
Parameters
- row and column are the INTEGER text coordinates of the SCREEN mode used.
- Optional colorflag INTEGER value can be omitted or 0 for ASCII code values or 1 for color attributes.
Usage:
- The code value returned is the ASCII code from 0 to 255. Returns 32(space) when no character is found at a coordinate.
- If the colorflag value is omitted or it is 0, the function returns the ASCII code of the text character at the position designated.
- When the flag value is greater than 0 in SCREEN 0, the function returns the foreground and background color attribute of text position.
- The foreground color(0 to 15) is the returned SCREEN color value AND 15: FG = SCREEN(1, 1, 1) AND 15
- The background color(0 to 7) is the returned SCREEN color value \ 16: BG = SCREEN(1, 1, 1) \ 16
- If BG color is > 7 then it indicates blinking FG (text) color, hence in that case substract 8 from the BG to get the correct background color and add 16 to the FG for the correct blinking color.
- QB64 can return color values in screen modes other than SCREEN 0. QBasic returned the wrong color values in graphic screen modes!
Example 1: Finding the text foreground and background colors in SCREEN 0 only:
SCREEN 0 COLOR 0, 15 CLS PRINT "SCREEN ="; SCREEN(1, 1, 1) PRINT "FG color:"; SCREEN(1, 1, 1) AND 15 'low nibble PRINT "BG color:"; SCREEN(1, 1, 1) \ 16 'high nibble |
SCREEN = 112 FG color: 0 BG color: 7 |
- Note: How the SCREEN 0 background color can only be changed to colors 0 through 7! 7 * 16 = 112.
Example 2: Reading the ASCII code and color of a text character using the SCREEN function. Graphic colors were not reliable in QBasic!
SCREEN 12 row = 10: column = 10 COLOR 9: LOCATE row, column: PRINT "Hello" code% = SCREEN(row, column, 0) ' character code return parameter 0 attrib% = SCREEN(row, column, 1) ' character color return parameter 1 COLOR 14: LOCATE 15, 10: PRINT "ASCII:"; code%, "COLOR:"; attrib% END |
Hello ASCII: 72 COLOR: 9 |
- Explanation: The SCREEN function returns the ASCII code for "H" and the color 9.
Example 3: Finding the current program path placed on the screen using FILES and the SCREEN function in SCREEN 0.
SCREEN 0, 0, 0, 0 CLS PRINT "This is a directory test..." SCREEN 0, 0, 1, 0 COLOR 0 'blank out the screen text FILES "qb64.exe" 'the current program's filename can also be used FOR i = 1 TO 80 a$ = a$ + CHR$(SCREEN(1, i)) 'scan the black text on the screen NEXT CLS COLOR 7 a$ = RTRIM$(a$) SLEEP SCREEN 0, 0, 0, 0 LOCATE 3, 1: PRINT "The current directory is: "; a$ END |
- Explanation: The SCREEN page one is used to hide the FILES display using COLOR 0. The SCREEN function reads the top of the screen page text and creates the current path string. It is then printed on the visual page.
See also