The World of DOS
It’s easy to forget how quickly technology changes our world. It’s only been a couple of decades since personal computers arrived and the world of Information Technology has changed a number of times since then.
Before the arrival of Windows, the ancestors of our modern machines ran different flavours of “Disk Operating Systems”. Microsoft was only one of a number of firms that produced versions of DOS which was a command line driven platform (everything had to be done through typing). No one manufacturer was dominant in producing operating systems. Amiga, Atari, BBC, Acorn, Microsoft, Commodore and Apple all competed with each other for a slice of the home market.
The workplace was not as diverse. Many applications were either run directly of mainframes (specialised, centralised computers) or servers. Applications that did exist on workstations tended to be DOS based and could be copied easily from one machine to another with a simple typed command.
By the start of the 1990’s Microsoft became the clear leader of companies competing with DOS based systems by producing menu systems that ran on top of their version of DOS that allowed a much greater use of a mouse and a Graphical User Environment. The almost revolutionary version of this platform was Windows for Workgroups 3.11 that allowed networked, business computers to run DOS applications and have a graphical display.
Other manufacturers had products that produced a GUI very similar to Windows. Xerox is accredited with the first modern GUI in 1981 and Apple followed in 1984 and the IBM / Microsoft partnership with OS2 in 1988. The major importance for Microsoft with it’s Windows product is that many of the business applications that were used on DOS could still run with their new GUI based operating system. Windows 3.11 applications were normally installed by just copying files from one directory to the hard drive of the local machine. Sometimes configuration files (INI’s) would need to be edited but the installation of applications could be achieved without any special tools and just some knowledge of DOS.
Developing for DOS – The Limitations of 3.11
Windows 3.11 was a major success for Microsoft. The cost of personal computers continued to drop and the market for new applications increased. Before the start of the 1990’s, many computers in the office had very little power at all. Everything done from these “Dumb Terminals” was actually run off another machine elsewhere with the local machine doing little more than sending and receiving commands.
The age of the Personal Computer was well underway and an explosion of applications that could be used on DOS or Windows based machines was taking place. The explosion in development was itself causing problems for the Operating System. When DOS is used to run applications, it expected additional resources or programs to be in the same folder as itself. Alternatively, a list of other folders that needed to be checked (should the application call something) was called the PATH. The number of folders that could be looked in by the Operating system was limited so when one application added a directory to the path, another existing directory would be forced to drop off it.
Libraries and resources could only be identified by their name and with a limited number of likely names in English which were themselves limited to being lengths of 8 characters long, applications started conflicting with each other as asking the Operating System for an application or library name could return file names from a number of different applications residing in the path. Exactly how resources were called had to change and there had to be a way of making resource names completely unique.
Introducing a new Display based environment meant that a lot more settings needed to be recorded for applications to work correctly. Text based INI files were not practical for storing the large amount of information that needed to be accessed quickly by running applications.
Windows 3.11 represented the end of the DOS computing environment and would give way to a new version of Windows that overcame these limitations with an innovation called the Registry.
Introducing the Registry
Windows 3.11 may have been the Operating System that saw Microsoft triumph over the World of DOS but the introduction of Windows 95 would be an innovation that would effectively give Microsoft a monopoly of personal computers.
Windows 95 had a number of advantages over its predecessor. The new database it used called the Registry was a fundamental technology introduction that would overcome the problems of Windows 3.11 and introduce new problems of its own. Windows was no longer just a shell that ran on DOS, its fundamental workings were independent of DOS (even though you couldn't run Windows 95 with DOS taken away).
The marketing campaign behind Windows 95 was enormous and can’t be underestimated as a reason for the future success of the Operating System.
With the spectacular arrival of the new operating system, new ways of working had to be devised.
The operating system no longer used file names to track which files had pieces of code in them. This would all now be done in a system database called the Registry.
• Values in the Registry could be used by all Windows 95 applications.
• All libraries (files with code in them) would have their details written to the Registry
The Registry would use unique numbers to identify code routines. These unique numbers are called Global Unique Identifiers (GUID’s). When a modern application runs, code is executed by Windows linking GUID’s back to physical files no the workstation and routines or “entry points” within those files.
The Registry could be accessed through the inbuilt utility the Registry Editor.
The new problem was that unlike the older DOS applications, technical support staff could no longer hope to just copy a directory of files from a server to a Personal Computer and hope for the applications to work.
The creation of the Registry meant that an application may create hundreds or thousands of Registry keys during a successful installation. Tools would now be needed to capture all the Registry keys altered and added to the Registry database so they could be added to other workstations when the files were copied into place.
Application Packaging for Windows 95
Toward the end of the 1990’s, two approaches had emerged for installing applications onto Windows 95.
One approach was to script key-strokes and run a vendor supplied installer as if someone were sitting at the keyboard. This approach had issues with timing as some machines would run at faster rates than others. There was little fault tolerance, if something unexpected happened everything became messed up.
Another approach was to capture all the changes made on one workstation and duplicate the changes to all others. Microsoft released a free version of Wise Installer (branded SMS Installer 1.0) to allow administrators to capture and roll out Registry changes. The utility was easy to use and by default, wouldn’t use much logic in branding a target machine with File and Registry key changes.
Poorly made installers had the ability to destroy a workstation. No real standards existed on the best way to install applications and packaging was a real art form based on the preferences of those charged with getting applications onto desktops.
Again Microsoft would be revolutionising the way we installed applications. With the development of Office 2000 came Windows Installer.
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