Q43527: BASIC Program to Read Characters from the Screen into a String
Article: Q43527 Product(s): See article Version(s): 4.00 4.00b 4.50 Operating System(s): MS-DOS Keyword(s): ENDUSER | B_BasicCom | mspl13_basic Last Modified: 14-DEC-1989 The program below demonstrates a method to read text that is printed on the screen into a BASIC string variable. The program accesses video memory (at segment B000 hex) to read the characters from the screen. This information applies to Microsoft QuickBASIC Versions 4.00, 4.00b, and 4.50, to Microsoft BASIC Compiler Versions 6.00 and 6.00b, and to Microsoft BASIC PDS Version 7.00. For a color display, you must change the address of the DEF SEG statement in the function from HEX B000 to HEX B800. Note that any attributes (blinking, highlight, etc.) will be lost when the text is put into the string. The program is as follows: DECLARE FUNCTION readstr$ (xline%, xstart%, xstop%) CLS PRINT "Now is the time" 'Put some text on the screen PRINT "for all good men" PRINT "to come to the aid" PRINT "of their country." a$ = readstr$(1, 1, 6) 'Read the first six characters of the 'first line (i.e. "Now is") b$ = readstr$(4, 10, 18) 'Read the last nine characters (10-18) 'on line four (i.e. "country.") LOCATE 10, 1 PRINT "A$ = "; a$ PRINT "B$ = "; b$ 'readstr$ takes three integers and returns a string. 'The integers are: 1) The line on the screen to read from ' 2) The starting character position ' 3) The ending character position 'It returns a string containing the characters on the screen 'on the specified line between the start and stop positions. ' FUNCTION readstr$ (xline%, xstart%, xstop%) DEF SEG = &HB000 'Change to B800 for color display fstart% = (160 * (xline% - 1)) + (2 * (xstart% - 1)) fstop% = (160 * (xline% - 1)) + (2 * (xstop% - 1)) FOR x% = fstart% TO fstop% STEP 2 s$ = s$ + CHR$(PEEK(x%)) NEXT x% readstr$ = s$ END FUNCTION
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