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# Device Driver Start Codes

Article ID: 101502

Article Last Modified on 11/1/2006

APPLIES TO

- Microsoft Windows NT Advanced Server 3.1
- Microsoft Windows NT Workstation 3.1
- Microsoft Windows NT Advanced Server 3.1

This article was previously published under Q101502

## SUMMARY

Windows NT device drivers define the following start codes:

- Boot
- System
- Auto
- Demand
- Disabled

The text below provides additional details about each of these start codes.

### Boot

The Boot start code indicates that the OS loader loads the driver at boot time before the executive system receives control. The disk driver for the system disk is an example of a Boot driver. If the system cannot load a Boot driver it cannot load the other drivers.

### System

The System start code indicates that the I/O system loads the driver during initialization. The mouse driver is an example of a System driver.

### Auto

The Auto start code indicates that the Service Controller loads the driver during its initialization. The parallel part driver is an example of an Auto driver.

### Demand

The Demand start code indicates that the Service Controller loads the driver only when it is explicitly instructed to do so. By default, Windows NT does not use any Demand drivers. You might create a Demand driver by loading the parallel port driver only when you want to print a document or only when a specified printer is available.

### Disabled

The Disabled start code indicates that the system does not load the driver. Windows NT sets the Disabled start code for all drivers in the system that it does not load (because corresponding hardware is not installed or for any other reason).

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