Q21901: COMSPEC; SHELL "Illegal Function Call", Can’t Find COMMAND.COM

Article: Q21901
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 | mspl13_basic
Last Modified: 29-DEC-1989

Customers who have floppy disk drive systems frequently find that the
SHELL command fails in the QuickBASIC editor or in a program running
on the system because QuickBASIC cannot find COMMAND.COM.

Note that the SHELL command will work reliably only under DOS Version
3.00 or later.

Failure to locate COMMAND.COM during a SHELL can generate one of the
following errors:

1. The error message "File not found"

2. The error message "Could not load COMMAND.COM"

3. The error message "Illegal Function Call"

4. A refusal to SHELL

A program needs to find COMMAND.COM before it can execute a SHELL
statement. The SHELL command in the File menu in the editor in
QuickBASIC Version 2.00, 2.01, 3.00, 4.00, 4.00b, or 4.50 also needs
to find COMMAND.COM before executing.

QuickBASIC looks first for COMMAND.COM in the directory specified by
the system COMSPEC environment variable and then in the current
directory.

The COMSPEC environment variable can be set by the MS-DOS SET command
in your AUTOEXEC.BAT file or in the MS-DOS command line, as follows:

   SET COMSPEC=drive:\directory

To tell MS-DOS where to find COMMAND.COM, you can also specify the
following command in your MS-DOS Version 3.20 CONFIG.SYS file (which
is executed at boot time):

   SHELL=A:\COMMAND.COM /E:1000 /P

In the above command, /E:size sets the size (in bytes) for MS-DOS
environment space, and /P tells the command processor that it is the
first program in the system so that it can process the MS-DOS EXIT
command. This SHELL= statement may not work under MS-DOS Version 3.30,
but works properly under MS-DOS Version 3.20. Under MS-DOS Version
3.30, you need to use SET COMSPEC.

This article applies to QuickBASIC Versions 2.00, 2.01, 3.00, 4.00,
4.00b, and 4.50 for the IBM PC and compatibles, Microsoft BASIC
Compiler Versions 6.00 and 6.00b for MS-DOS, and Microsoft BASIC PDS
Version 7.00 for MS-DOS.

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