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Q68224: BASIC Program to Reboot or "Cold" Reboot the Machine

Article: Q68224
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S901024-65 restart boot S_C S_QuickC B_BasicCom | mspl13_basic
Last Modified: 15-JAN-1991

This article gives two ways to reboot your machine from within a BASIC
program.

WARNING: Please be sure to CLOSE all open files before rebooting the
computer, so as not to lose buffered data.

This information applies to Microsoft QuickBASIC 4.00, 4.00b, and
4.50; to Microsoft BASIC Compiler 6.00 and 6.00b for MS-DOS; and to
Microsoft BASIC Professional Development System (PDS) 7.00 and 7.10
for MS-DOS.

Method 1
--------

The first method of rebooting the machine requires only BASIC code.
This program sends a command directly to the keyboard I/O port using
BASIC's OUT statement. This causes the keyboard controller chip to
reboot the machine just as if you had typed CTRL+ALT+DEL on the
keyboard. Note that this command is supported only on the AT and
higher class of machines. This example will not work on the IBM PC- or
XT-class machines or clones.

' REBOOT.BAS
DEFINT A-Z
DEF SEG = &H40      ' If the memory location &H0072:0073 in the BIOS
POKE &H72, &H34     ' data area contains &H1234, then this will cause
POKE &H73, &H12     ' a warm reboot (no self test or memory
                    ' count). Anything else causes does a cold reboot
                    ' (self test and memory count).
DEF SEG             ' Return to BASIC's default segment.
Command% = &HFE     ' Reset Processor command.
Port% = &H64        ' Keyboard I/O Port
OUT Port%, Command% ' Reboot

Method 2
--------

Another way to reboot your machine is to jump directly to the ROM BIOS
initialization code (which normally executes automatically when the
machine's power is first turned on). This method of rebooting the
machine should work on all members of the IBM PC and PS/2 family of
computers, as well as the clones of these machines.

In order to do this, however, your chosen language must have support
for "pointers to functions" as in C or assembly. Because BASIC does
not support a function pointer data type, you must write a C or
assembly procedure to jump to the ROM BIOS boot code. You can call
this C or assembly procedure from your BASIC program.

Two separate articles in the Microsoft Knowledge Base describe how to
reboot the MS-DOS computer. One article uses C alone to reboot, and
one article uses C with inline assembly code to reboot. Search for
these two articles using the following words:

   reboot and machine and QuickC

For more information about calling C from BASIC, search on the word
BAS2C. For more information about calling assembly language from
BASIC, search on the word BAS2MASM.

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