Microsoft KB Archive/75095

= CLS Does Not Clear Screen on AT&T 6300 =

Article ID: 75095

Article Last Modified on 5/12/2003

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APPLIES TO


 * Microsoft MS-DOS 5.0 Standard Edition
 * Microsoft MS-DOS 5.0a
 * Microsoft MS-DOS 6.0 Standard Edition
 * Microsoft MS-DOS 6.2 Standard Edition
 * Microsoft MS-DOS 6.21 Standard Edition
 * Microsoft MS-DOS 6.22 Standard Edition

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This article was previously published under Q75095



SYMPTOMS
After starting an AT&T 6300, MS-DOS uses only one line of the screen to display commands such as DIR, TREE, and so on; however, the startup information remains on the screen even after issuing the CLS command. In the other cases, the system will hang at the DOS prompt after pressing ENTER a few times.



WORKAROUND
To work around this problem, add the following line to the CONFIG.SYS file, or use the debug script listed below. device=ansi.sys /s The same behavior occurs on AT&T 6310 machines.



MORE INFORMATION
The ANSI.SYS /S switch is an undocumented switch that will force the video to display in 25-line mode. MS-DOS 5.0 or 6.0 relies on byte 40h:84h of the BIOS to work in 43/30 line mode. The earlier version of MS-DOS did not use this byte. The following is a short program to patch the BIOS area into having the 25 (actually 24, because it is is 0-based) value required for a CGA/MDA adapter.

At the DOS prompt, type debug.

You will then see the Debug prompt (a hyphen). Type the following, pressing ENTER after each line: Debug             User Response          Input -

C:\>              debug -                 n patch.com -                 a xxxx:xxxx          mov ax,40 xxxx:xxxx         mov es,ax xxxx:xxxx         es: xxxx:xxxx         mov byte ptr [84],18 xxxx:xxxx         int 20 xxxx:xxxx           -                 r cx
 * d

-                 w -                  q This will create PATCH.COM, a file you can execute from the command prompt. If the problem is resolved, put an entry to execute the PATCH.COM file in the AUTOEXEC.BAT file.

Additional query words: 6.22 boot ATT att6300 scroll scrolling 5.00 5.00a 6.00 6.20

Keywords: KB75095

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