Printing ASCII Characters > 127 Fails in CGA Mode

ID: Q43272

5.10 6.00 6.00a 6.00ax 7.00 | 1.00 1.50

MS-DOS                      | WINDOWS

kbenv

The information in this article applies to:

The C Run-time (CRT) included with:

    - Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, and 6.0ax
    - Microsoft C/C++ for MS-DOS, version 7.0
    - Microsoft Visual C++ for Windows, versions 1.0 and 1.5

When a CGA graphics card is in any CGA graphics mode it does not display ASCII characters greater than 127 when Microsoft C text-output routines are used. Garbage characters are displayed instead.

This is expected behavior. The default character-definition table for CGA graphics cards contains only the first 128 ASCII characters. To print ASCII characters 128 to 255, a separate character-definition table must be set up and accessed through Interrupt vector 1FH. The MS-DOS utility GRAFTABL leaves such a table and hooks the Interrupt 1FH vector to point to it.

For more information, see Richard Wilton's book "Programmer's Guide to PC & PS/2 Video Systems," page 269, which is available from Microsoft Press.

Additional reference words: kbinf 6.00 6.00a 6.00ax 7.00 1.00 1.50 KBCategory: kbenv KBSubcategory: CRTIss Keywords : kb16bitonly

Last Reviewed: July 18, 1997