Windows 95 was the Microsoft’s most popular 32-bit desktop operating system, which replaced the Windows 3.1 operating system. Windows 95 was designed as a desktop operating system for home, office, and business use that preserves full backward compatibility with applications for legacy 16-bit operating systems such as MS-DOS, Windows 3.1, and Windows for Workgroups.
Graphic W-5. Windows 95 Desktop.
Windows 95 includes the following features:
The Windows 95 architecture evolved from Windows 3.1 and Windows for Workgroups, but in contrast to these 16-bit versions of Windows, which ran on top of MS-DOS, Windows 95 is a 32-bit operating system with a 32-bit kernel, VxDs, and an Installable File System (IFS) manager and does not require that MS-DOS be loaded on the computer. However, Windows 95 does includes some 16-bit code and 16-bit components to ensure backward compatibility with MS-DOS, Windows 3.1, and Windows for Workgroups. Windows 95 also supports multithreaded operation and preemptive multitasking operation and manages system resources more effectively than earlier versions of Windows, allowing more and larger applications to be multitasked.
Graphic W-6. Architecture.
For added protection against application crashes, Windows 95 supports virtual machines (VMs). VMs in Windows 95 are similar to those implemented in Windows 3.1 except for two differences: in Windows 95, 32-bit Windows applications (Win32 apps) can run within their own protected memory address space within the system VM, and 16-bit Windows applications (Win16 apps) also run in the system VM but share their own address space (since they must be cooperatively multitasked). MS-DOS applications run in individual VMs of their own.
Another change in Windows 95 is that system configuration information that was formerly stored in boot files (config.sys and autoexec.bat) and INI files is stored in a database structure called the registry. The registry is the central repository for all hardware and software configuration information. Boot and INI files are still supported for backward compatibility with legacy hardware and software.
Windows 95 went through several incremental releases, each with additional features and enhancements. To determine which version of Windows 95 you are using, run the System utility in Control Panel and look at the version number on the General tab. The incremental versions are described in the following table.
Original full retail version and upgrade from Windows 3.1.
Windows 95 with Service Pack 1, also called OEM Service Release 1 (OSR1).
OEM Service Release 2 (OSR2) or OEM Service Release 2.1 (OSR2.1). If “USB Supplement to OSR2” shows up as an installed program when you use the Add/Remove Programs utility in Control Panel, you have OSR2.1 installed.
OEM Service Release 2.5 (OSR2.5).
If your 20-digit product ID number has “OEM” in it, you have an original equipment manufacturer (OEM) version of Windows 95 that was probably preinstalled on your computer.