Windows 95 Blueprint: Internals and Architecture
In this particular chapter, we will take a look behind the scenes at Windows 95 and see how it works. We'll discuss how memory, applications, and the infamous Registry works in Windows 95. Let's take a look at the exam objectives.
Compare and contrast the memory usage of a Microsoft MS-DOSbased application, a 16-bit Windows-based application, and a 32-bit Windows-based application operating in Windows 95. Configure Windows 95 to run MS-DOSbased applications.
Predict potential problems when configuring 16-bit Windows-based applications.
Configure Windows 95 to run MS-DOSbased applications.
Distinguish between MS-DOS Mode and the standard method for running MS-DOSbased applications.
Determine when you should run an application in MS-DOS mode.
Resolve general protection faults.
Determine the appropriate course of action when the application stops responding to the system.
Define the purpose of the Registry.
Classify types of information in the Registry.
Determine where the Registry is stored.
Identify situations in which it is appropriate to modify the Registry.
Modify the contents of the Registry.
3.1.2. Fast Facts
A virtual machine simulates an entire computer's resources to an application.
All system processes, Windows 16-bit applications, and Windows 32-bit applications run in a single virtual machine called the system virtual machine.
Each MS-DOS program runs on separate virtual machine called a MS-DOS virtual machine.
A 16-bit application can send the processor only one thread of code at a time for execution.
A 32-bit application can send the processor multiple threads of code at a time for execution.
When one 16-bit application stops responding, all 16-bit applications stop responding. The 32-bit applications are not affected. Ending the hung up application will cause other 16-bit applications to respond once again.
When a 32-bit application stops responding, no other applications are affected.
You can modify the behavior of an MS-DOS virtual machine by editing the program information file (PIF) of an MS-DOS executable program.
HKEY_LOCAL_MACHINE is the Registry key that contains all machine-specific information, such as drivers and hardware.
REGEDIT.EXE is the program used for viewing and editing the Registry directly, but the preferred method for editing the Registry is through normal use of applets in the Control Panel.
Real mode MS-DOS drivers usually have a SYS extension. Real-mode Windows drivers usually have a DRV extension and are listed in the SYSTEM.INI. Protected mode Windows drivers usually have a VXD or 386 extension.