Q26088: No Cursor Displayed in Graphics SCREENs 1, 2, 3, 7 through 13

Article: Q26088
Product(s): See article
Version(s): 1.00 1.01 1.02 2.00 2.01 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom B_GWBasicI | mspl13_basic
Last Modified: 26-OCT-1989

When you poll the INKEY$ function, a blinking cursor is displayed only
in SCREEN 0 (text mode), and not in any graphics screen mode. A
blinking cursor is not displayed in SCREEN 1, 2, 3, 7, 8, 9, 10, 11,
12, or 13 (please see the SCREEN statement in your BASIC language
reference manual to find out which SCREEN modes your version of BASIC
supports). This is a hardware video-graphics limitation, not a
limitation of BASIC. This information applies to Microsoft QuickBASIC
Versions 1.00, 1.01, 1.02, 2.00, 2.01, 3.00, 4.00, 4.00b, and 4.50 for
MS-DOS, to the Microsoft BASIC Compiler Versions 6.00 and 6.00b for
MS-DOS and OS/2, and to Microsoft GW-BASIC Versions 3.20, 3.22, and
3.23.

In graphics modes, to get a cursor (which will be non-flashing and
block-shaped), you can use the INPUT or LINE INPUT statement. You may
also design a program that draws a cursor.

The following program does not display a blinking cursor in SCREEN
modes other than 0:

   SCREEN 9 ' using SCREEN 0 lets you see cursor.
   LOCATE 1, 1, 1 ' Try to turn on the cursor
   PRINT "t": CLS
   10 a$ = INKEY$
   IF a$ = "" THEN GOTO 10

Using SCREEN 0, you get a blinking, underscore-shaped cursor while the
INKEY$ function is being polled.

There is a more detailed explanation of this text-mode cursor in the
"Video Basics" chapter of Peter Norton's "Programmer's Guide to the
IBM PC," published by Microsoft Press (see Page 92 of the 1985 edition
and Page 94 of the 1988 edition).

The blinking, underscore-shaped cursor is a feature of the text modes
(i.e., SCREEN 0 only) and is created by hardware. To have a cursor in
graphics mode, you must draw it within your program.

Below is an example of drawing a graphics mode cursor in SCREEN 9. It
uses the underscore character, clears the screen, and starts over
after you reach line 25, column 80.

SCREEN 9
CLS
PRINT "_"
y% = 1 ' Start at row 1
WHILE 1
a$ = INKEY$
IF a$ <> "" THEN
  x% = POS(0)
  LOCATE y%, x%
  PRINT a$;
  IF x% < 80 THEN
     PRINT "_";
     LOCATE y%, x% + 1
  ELSEIF y% = 25 THEN
      y% = 1
      x% = 0
      CLS
  ELSE
    y% = y% + 1
    x% = 0 ' Set the column to zero.
  END IF
END IF
WEND

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