Running Win16 Applications

The 16-bit Windows subsystem runs 16-bit Windows-based applications, which you can launch from My Computer, Windows NT Explorer, or from the command prompt. There are no user-visible distinctions between 16-bit and 32-bit Windows-based applications.

Restrictions on Win16 Applications

This section describes the few restrictions that apply to running applications under the 16-bit Windows subsystem:

• All MS-DOS functions except task-switching APIs (application programming interface functions) are supported.

• Block mode device drivers are not supported. (Block devices are not supported, so MS-DOS IOCTL APIs that deal with block devices and SETDPB functions are not supported.)

• Interrupt 10 function 1A returns 0; all other functions are passed to read-only memory (ROM).

• Interrupt 13 calls that deal with prohibited disk access are not supported.

• Interrupt 18 (ROM BASIC) generates a message that says ROM BASIC is not supported.

• Interrupt 19 will not reboot the computer, but will cleanly terminate the current virtual DOS machine (VDM).

• Interrupt 2F dealing with the DOSKEY program call outs (AX = 4800) is not supported.

• Microsoft CD-ROM Extensions (MSCDEX) functions 2, 3, 4, 5, 8, E, and F are not supported.

• The 16-bit Windows subsystem on an x86 computer supports Enhanced mode applications; it does not, however, support 16-bit VXDs (virtual device drivers). The subsystem on a non-x86 computer emulates the Intel 40486 instruction set, which lets the computer run Enhanced mode applications, such as Visual Basic®, on RISC computers.

Terminating the Subsystem

If an ill-behaved application locks up the 16-bit Windows subsystem, you can terminate the subsystem.

To terminate the 16-bit Windows subsystem

1. Press ctrl+shift+esc to display Task Manager.

2. Click the Applications tab.

3. Click to select the application.

4. Click End Task.

If the application does not respond, an additional dialog box appears giving you the option to wait or to end the task.