Operating System & Procedures

Order of Operations:

When a computer is first turned on it goes through a series of self tests called the P.O.S.T. (power on self test).  BIOS (basic input/output system) is the pre-operating system capability statement for a given computer.  CMOS (complimentary metal oxide semiconductor) allows the end user to setup special changes in the way a computer performs (Usually F2 key places you in setup at the time of booting).

Two major companies that manufacture BIOS are AMI & Phoenix Technologies.

First Operating System for the PC -- DOS (Disk Operating System).  Created by Microsoft.

DOS did only one thing at a time, 16 bit instructions.  No memory operation within system.  Game software drives the industry...so better and better operating systems were demanded for more complex instructions.  Windows 3.0, 3.1 were actually not true operating systems.  They both ran on top of DOS.

32-bit programs - Unix, OS/2, late 80's Microsoft, IBM, 3M began work on more stable operating system.

Windows NT (New Technology) was a 32-bit operating system, multi-tasking, but applications run in separate memory spaces, so if Word dies, only the program died, not the entire machine shutting down.  WinNT is a modular system.  Things can be plugged / unplugged without affecting the hardware.  Most DOS programs will run on NT, except those that have direct calls to the hardware.  WinNT buffers any application from direct access to the hardware.

IRQ

Interrupt Requests to the Bus are unique addresses for each device. 

Examples:

End user must be careful to add devices without using IRQs that do not conflict with existing devices.

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