Microsoft KB Archive/27101

Batch File Environment Variables and DOS Version 2.x ID Number: Q27101

5.00 5.10 5.10a MS-DOS

Summary:

SYMPTOMS The batch files that come with Microsoft Macro Assembler (MASM) version 5.0, 5.1, and 5.1a use environment variables (i.e., %var%) to set various configuration variables. Under MS-DOS versions 2.x, when %var% should evaluate to NULL, it will actually be evaluated as “var%”, ignoring the first “%” and causing errors, as would be expected.

These batch files include the following:

DEMO.BAT SETUP.BAT RUNME.BAT SETUP2.BAT MAKESHOW.BAT CAUSE This environment variable feature was not supported before MS-DOS versions 3.0.

RESOLUTION Workarounds for this problem would be to either update DOS to a 3.x version or later, or edit the batch files to eliminate those variables that would be set to NULL.

STATUS Later versions of MASM require MS-DOS version 3.0 or later.