A+: More on Operating Systems

Multi-tasking and task switching:

  Task switching looks like your computer is doing many things at once, but really it just puts one program on hold and changes to another when you ask for it. 

  Co-operative multi-tasking was an early Windows method which waited for the application running to control and release resources such as memory, but when that program failed, your computer locked up.

  Preemptive multi-tasking is more sophisticated; the OS now schedules when a program can use resources, and takes back control of resources to give to other programs. If one application locks up, other programs also running don't suffer. 

Windows processor features and memory:

  Multi-threading allows one CPU (Central Processing Unit, the central chip of personal computers) to look to Windows as if it were multiple CPUs. Multi-threading first reached the desktop in 2002 with the 3.06 GHz version of Intel's Pentium 4. Also known as Hyper-Threading, it's also included in Intel's Atom low power processors as well as the Core i7.

  CPUs labeled as x86 are Pentiums; 32-bit CPUs can run 32-bit programming, with a Microsoft-imposed limit of 4GB of memory (from which one must subtract the video card memory since it shares the same memory space). x64 AKA 64-bit CPUs can run 64-bit operating systems and applications, and the 64-bit version of Windows 7 Pro has a limit of 192GB, whereas Windows Server 2008 is capped at 8GB-2TB depending on the version.

The foundation of Windows:

  Windows was developed by Microsoft using principles created in 1974 and first shown in the Xerox Alto, a machine never commercially sold. The Apple Macintosh also used Xerox's innovations from the Alto.  

  Version 1.0 shipped in 1985, despite IBM's focus on OS/2, a competing windowing system with much better integration of the Graphical User Interface ('GUI') into the operating system. By contrast, Windows ran atop MS-DOS, and the two were not integrated until Windows 95 and Windows NT.

Compatibility:
  Microsoft publishes a Hardware Compatibility List for its different versions, which will be replaced by a Windows Catalog. It shows the user whether their computer and its components are compatible with the next version of Windows, and microsoft.com/whdc/hcl/search.mspx has the Windows 7 version.

Before installing an OS:
  1. Check for the OS minimum requirements and hardware compatibility
  2. Choose the installation options (manual? automatic? cloning?)
  3. Choose the installation method (from CD? DVD? Memory drive? Over-the-wire?)
  4. Prepare the PC for installation