QB64-PE/internal/help/SCREEN_(function).txt

The '''SCREEN''' function returns the [[ASCII]] code of a text character or the color attribute at a set text location on the screen.


{{PageSyntax}}
:: 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 zero for [[ASCII]] code values or 1 for colors.


''Usage:''
* The ''code'' value returned is the [[ASCII]] code from 0 to 255. Returns 32([[SPACE$|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, the function returns the foreground color attribute of the text character position.
* '''QB64''' can return color values in screen modes other than [[SCREEN]] 0. Qbasic returned the wrong color values in graphic screen modes!


''Example 1:'' Reading the [[ASCII]] code and color of a text character using the SCREEN function. Graphic screen colors were not reliable in Qbasic!
{{CodeStart}} '' ''
{{Cl|SCREEN (statement)|SCREEN}} 12
row = 10: column = 10

{{Cl|COLOR}} 9: {{Cl|LOCATE}} row, column: {{Cl|PRINT}} "Hello"
code% = {{Cl|SCREEN (function)|SCREEN}}(row, column, 0)     ' character code return parameter 0
attrib% = {{Cl|SCREEN (function)|SCREEN}}(row, column, 1)   ' character color return parameter 1
{{Cl|COLOR}} 14: {{Cl|LOCATE}} 15, 10: {{Cl|PRINT}} "ASCII:"; code%, "COLOR:"; attrib%
{{Cl|END}} '' ''
{{CodeEnd}}
{{OutputStart}}
{{Text|         Hello|blue}}



{{Text|         ASCII: 72     COLOR: 9|yellow}}
{{OutputEnd}}
:''Explanation:'' The SCREEN function returns the [[ASCII]] code for "H" and the color 9.


''Example 2:'' SCREEN 0 will return the values for both foreground and background colors. The combined color attribute value is returned.
{{CodeStart}} '' ''
{{Cl|SCREEN}} 0
row = 10: column = 10

{{Cl|COLOR}} 9, 10: {{Cl|LOCATE}} row, column: {{Cl|PRINT}} "Hello" 'use the background color of bright green
code% = {{Cl|SCREEN (function)|SCREEN}}(row, column, 0) ' character code return parameter 0
attrib% = {{Cl|SCREEN (function)|SCREEN}}(row, column, 1) ' character color return parameter 1
{{Cl|COLOR}} 14, 0: {{Cl|LOCATE}} 15, 10: {{Cl|PRINT}} "ASCII:"; code%, "{{Cl|COLOR}}:"; attrib%

fg% = (attrib% {{Cl|AND (boolean)|AND}} {{Cl|&H}}F) 'get the lower nibble
bg% = (attrib% {{Cl|AND (boolean)|AND}} {{Cl|&H}}F0) / 16 'get the upper nibble
{{Cl|IF...THEN|IF}} bg% > 7 {{Cl|THEN}} 'MSB set in the bg% nibble indicates blinking fg%
  fg% = fg% + 16
  bg% = bg% - 8
{{Cl|END IF}}
{{Cl|LOCATE}} 20, 10:{{Cl|PRINT}} "FG:"; fg%, "BG:"; bg% '' ''
{{CodeEnd}}{{small|Contributed by RhoSigma}}
{{OutputStart}}
{{Text|         Hello|blue}}



{{Text|         ASCII: 72     COLOR: 41|yellow}}


{{text|         FG: 9         BG: 2|yellow}}
{{OutputEnd}}
:''Note:'' SCREEN 0 background colors are limited to colors 0 to 7 so [[COLOR]] 10 is converted to attribute 2 (8 less than the high intensity background color value of 10).


''Example 3:'' Finding the current program path placed on the screen using [[FILES]] and the SCREEN function in SCREEN 0.
{{CodeStart}} '' ''
{{Cl|SCREEN}} 0, 0, 0, 0
{{Cl|CLS}}
{{Cl|PRINT}} "This is a directory test..."
{{Cl|SCREEN}} 0, 0, 1, 0
{{Cl|COLOR}} 0 'blank out the screen text
{{Cl|FILES}} "qb64.exe"        'the current program's filename can also be used
{{Cl|FOR...NEXT|FOR}} i = 1 {{Cl|TO}} 80
  a$ = a$ + {{Cl|CHR$}}({{Cl|SCREEN (function)|SCREEN}}(1, i)) 'scan the black text on the screen
{{Cl|NEXT}}
{{Cl|CLS}}
{{Cl|COLOR}} 7
a$ = {{Cl|RTRIM$}}(a$)
{{Cl|SLEEP}}
{{Cl|SCREEN (statement)|SCREEN}} 0, 0, 0, 0
{{Cl|LOCATE}} 3, 1: {{Cl|PRINT}} "The current directory is: "; a$
{{Cl|END}} '' ''
{{CodeEnd}}
{{small|Code by Pete from the N54 QB site}}
:''Explanation:'' The SCREEN page one is used to hide the [[FILES]] display using COLOR 0. The [[SCREEN (function)|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:'' 
* [[PRINT]], [[SCREEN]]
* [[COLOR]], [[CHR$]], [[POINT]]
* [[CSRLIN]], [[POS]], [[ASCII]]
* [[Screen Memory]]


{{PageNavigation}}