Operating System Design/Case Studies/Windows 9x
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Windows 9x references to the Windows family, Windows 95, 98 and Me operating systems. They were set apart from the earlier Windows versions: 1.0, 20, and 3.0 by their device drivers, virtual memory management and MSDOS.SYS and MS-DOS kernel. It wasn't until 2000 that a new kernel was written, called the NT Kernel that is still in use today.
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[edit] Architecture
The Windows 9x architecture was a step up in many ways from its predecessors. The GUI was redesigned, the kernel supported virtual memory and had a FAT32 and VFAT filesystem unlike its FAT16 and FAT12 filesystems before. The OS was one of the first GUI fully-32bit operating systems at the advent of the Pentium I.
[edit] The Kernel
The kernel was just a different version of the MS-DOS kernel, with added virtual memory and memory protection that was lacking in Windows 1.0+. It was of monolithic architecture, different from its successors NT 1.0+.
[edit] The Registry
The registry acted as a temporary and convenient holding place for program and system data. The directories are conventionally named as follows: HKEY_CLASSES_ROOT, HKEY_CUREENT_USER, HKEY_LOCAL_MACHINE, HKEY_USERS, HKEY_CURRENT_CONFIG, and HKEY_PERFORMANCE_DATA. Each one of these stored specific types of data like, hardware configuration data, application data, performance data, and user data. The system can access this anytime and the current user is allowed to access and edit it also.
[edit] File Names
File names in Windows 9x were allowed to have up to 255 characters, a special feature in the FAT32 filesystem. Previous versions of Windows (running on top of MS-DOS) were limited to MS-DOS style 8.3 letter filenames.
[edit] Graphical User Interface
The GUI was one significantly changed in the Windows 9x series, with a start button and a button bar along the bottom of the screen allowing a running program to be selected. There was also a new widget set (that is, a different standard look and feel to the applications) and many new fonts.
