FIX: PWB Extensions in MS-DOS Cannot Shell to MS-DOS

The information in this article applies to:

• Microsoft Programmer's Workbench for MS-DOS, versions 1.0 and 1.1

SYMPTOMS

Extensions written for the Programmer's WorkBench (PWB) versions 1.0 and 1.1 that require a call to the operating system do not work correctly under DOS. One example of this is the FILTER.C sample extension packaged with Microsoft C version 6.0.

CAUSE

When PWB.COM is executed under DOS, it spawns the main editor (PWBED.EXE). PWBED.EXE is cleared from memory when a DOS shell is run from within the editor. Once the shell has completed, PWBED.EXE is reloaded from disk and initialized. The initialization is what causes the problem because it also initializes any extensions to the editor at the same time. This means that any information that the extension was keeping track of is lost.

STATUS

Microsoft has confirmed this to be a problem in PWB versions 1.0 and 1.1. This problem was corrected in PWV version 2.0.