System software - basics

Systems Software is a collection of programs that help end users and application programs to operate and control a computer

Analogy - the office secretary

You might like to think of an operating system as an office secretary.

[Office secretary]

This secretary must

Manage the filing
Manage messages and requests from staff
Provide client contact with your organisation.
Manage room and resource bookings.

Finally, not all secretaries are the same, some are better at typing, or shorthand, or some other specialist skill. So generally we choose the secretary best for the job.

Analogy - Car driver

Or you might like to think of the Operating System as the driver of a vehicle.

If we relate;

Hardware The vehicle itself,

Data the luggage in the back,

People your passengers,

Procedures instructions on how the vehicle works

Software The driver of the vehicle

No matter what vehicle, whether car, truck, bulldozer, motorbike, there are some basic things the driver must know and do. These include things such as steer the vehicle, know what to do when it is switched on, manage the gears and so forth. This is the "SYSTEM" software knowledge.

Then depending on the type of vehicle other knowledge is required. For Example, a bulldozer requires knowledge of lifting the blade. This is like the "APPLICATION" Software.

So to return to a computer, the Operating system software consists of the BASIC instructions that manage its own resources. The are required by all applications

Resource management

An Operating System is like a translator between you and your computer. Basically this translator is a series of programs that let you communicate with your computer.

It manages system resources such as the CPU, primary memory, secondary memory (disk drives) and systems input and output devices such as the keyboard, screen, and printer.

It also provides the systems interface, which is the part of the system that interacts with you, the end-user of the computer. This is the part of the operating system you actually see, and through which you can control the computer.

System programs

[OS sales chart 1994]

The four basic system software programs
Bootstrap loader

Stored permanently in Read Only Memory (ROM)
Starts the computer when turned on and loads programs (such as the Operating System) into primary storage

Diagnostic routines

Tests parts of the system (such as memory, keyboard) to be sure the computer is running properly.

Basic Input output system (BIOS)

Service programs enabling the computer to interpret characters from the keyboard or to another peripherals (disk, monitor)

Operating System

Manages the computer resources. It includes programs utility programs for managing files and disks (copying, erasing, disk formatting).

16 v's 32 bit Operating Systems

16 bit OS

Use segmented memory that limits the amount of memory an application or component can access to 640K

32 bit OS

Memory model allows an application or component to access up to 4GB of memory, removing 16bit performance limitations.

Background and foreground tasks will operate with little degradation in performance.

Ref [130]Computerworld NZ June 95

Evolution

[OS evolution]

(The chart shows chronological evolution of personal computer operating systems and the influences and cross-influences over time. It is not meant to show specific product dependencies)

If a chicken ...

Why (and how) did the chicken cross the road? Well, that depends on which system developer laid the egg, according to the wit who created the following variation on the old theme.

OS/2 Chicken: It crossed the road in style years ago, but it was so quiet that nobody noticed.
Win95 Chicken: You see different coloured feathers while it crosses, but cook it and it still tastes like ... chicken.
Microsoft Chicken (TM): It's already on both sides of the road. And it just bought the road.
OOP Chicken: It doesn't need to cross the road, it just sends a message.
Assembler Chicken: First it builds the road ...
C Chicken: It crosses the road without looking both ways.
C++ Chicken: The chicken wouldn't have to cross the road, you'd simply refer to him on the other side.
VB Chicken: USHighways!TheRoad.cross(aChicken).
Delphi Chicken: The chicken is dragged across the road and dropped on the other side.
Java Chicken: If your road needs to be crossed by a chicken, the server will download one to the other side, (of course, those are chicklets).
Web Chicken: Jumps out on to the road, turns right, and just keeps on running.
Gopher Chicken: Tried to run, but got flattened by the Web chicken.
Newton Chicken: Can't cluck. Can't fly and can't lay eggs, but you can carry it across the road in your pocket.
Biggles Chicken: Nearly crosses the road but runs out of resources half way.
Cray Chicken: Crosses faster than any other chicken, but if you don't dip it in liquid nitrogen first, it arrives on the other side fully cooked.
Quantum Logic Chicken: The chicken is distributed probalistically on all sides of the road. Do not cross till you observe it on your side of the road.
Lotus Chicken: Don't you dare try to cross the road the same way we do!
Mac Chicken: No reasonable chicken owner would want a chicken to cross the road, so there's no way to tell it to.
COBOL Chicken:
0001-CHICKEN-CROSSING.
IF NO-MORE-VEHICLES
THEN PERFORM 0010-CROSS-THE-ROAD VARYING STEPS FROM 1 BY 1 UNTIL ON-THE-OTHER-SIDE
ELSE GOTO 0001-CHICKEN-CROSSING

The Dominion "IT Weekly #276 Nov 25 1996