|
|
|
Chapter 3 in Computing Essentials 2000-2001 (O’Leary
and O’Leary) |
|
|
|
|
|
Hardware consists of the parts of the computer
you can touch |
|
keyboard, mouse, monitor, printer, drives,
motherboard, CPU and so on |
|
Software is simply a set of instructions (a.k.a.
a program), it tells the hardware what to do and when to do it |
|
|
|
|
While the software (the instructions) are stored
on chips or disks, it is distinct from them |
|
Analogy: in the same way that a musical score is
distinct from the paper it’s printed on or the CD recording of it |
|
Hardware is the part of the computer you can
kick; if you can only curse at it it’s software |
|
|
|
|
An “interface” is a boundary or region of
contact between two entities and typically where any interaction or
exchange takes place |
|
The interface between the user and hardware is
multi-layered |
|
There are interfaces within interfaces |
|
|
|
|
The layer closest to the user consists of
“application packages” (like Word, Excel and PowerPoint) that help the user
perform particular tasks and high-level languages (like C, Basic, Pascal,
Fortran, etc.) |
|
the layer closest to the software is called the
BIOS (Basic Input/Output System) |
|
In between lies the “operating system” |
|
|
|
|
The BIOS is a set of instructions stored on a
read-only memory (ROM) chip |
|
It is sometimes called “firmware” since it
occupies the middle ground between software and hardware. (The instructions
are built right into the chip.) |
|
You may see the term BIOS on the screen soon
after you turn on the power |
|
|
|
|
It checks on (detects) the other parts: memory,
keyboard, mouse and so on |
|
Then it looks for the “boot program” that will
load the operating system |
|
It always looks to the floppy disk drive first,
which is why you shouldn’t have a floppy in the drive when you are booting
the system |
|
|
|
|
While it is most noticeable during the boot
process, the BIOS is used constantly |
|
This separation of BIOS from operating system
allows for changes in hardware without a major rewriting of the operating
system software |
|
|
|
|
If one has a new piece of hardware, the
interface instructions connecting it and the operating system may not be
written into the system’s ROM chip, the software (as opposed to firmware)
is needed |
|
This software is called a “device driver” |
|
|
|
|
Between
the high-level (user friendly) applications and the BIOS is the “system
software,” most notably the operating system but also language translators
and utilities |
|
The operating system consists of programs for
loading and executing applications, storing or retrieving files, managing
the CPU, switching between tasks and so on |
|
|
|
|
File Viewer: shows you the file or part thereof,
esp. if it’s a graphic file |
|
File Conversion: takes in one format and turns
it into a another |
|
File Compression: shrinks the size of stored
files |
|
Backup: makes a copy of your files in case of a
system crash |
|
|
|
|
Diagnostics: are things installed and working
properly? |
|
Uninstaller: gets rid of applications you no
longer want |
|
Anti-virus: seek and destroy virus, protection
too |
|
Screen Saver: it used to be that it literally
saved the screen, now mostly entertainment, sometimes security |
|
|
|
|
Desktop Enhancer: organizes desktop |
|
Internet manager: manage your website |
|
LANGUAGE TRANSLATOR: takes a programmer’s
high-level code and converts it to a binary code that computer components
“understand.” (Again this is done in several stages.) |
|
|
|
|
Command-line interface: the user types keywords (commands)
after a prompt |
|
Menu-driven interface: the user selects options
from a menu typically using the arrow and Enter keys |
|
Graphical User Interface (GUI): the user points
to icons with the mouse, etc. |
|
|
|
|
Especially with GUI interfaces, operating
systems have become rather large |
|
Once the boot program is loaded into memory, it
in turn loads the essential parts and the more frequently used commands (the
kernel) of the operating system |
|
The rest (the external commands) are loaded only
when needed |
|
|
|
|
|
Operating systems may be distinguished in
whether they allow |
|
multi-tasking |
|
multi-threading |
|
multi-users |
|
multi-processors |
|
|
|
|
A task or process is a program or part of a program the user wants
executed |
|
Modern operating systems are multi-tasking in
that they execute two or more applications running simultaneously (actually
they switch back and forth between the applications) |
|
Older single-tasking operating systems could
only do one thing at a time |
|
|
|
|
context switching: only one process is active,
but the status of the other process is preserved |
|
cooperative multitasking: switching occurs at
natural breaks in the process, but one application can take over |
|
preemptive multi-tasking: tasks are prioritized
and looked in on often so that one of them does not monopolize the CPU |
|
|
|
|
Multi-threading: similar to multi-tasking but
takes place within a single application, e.g. one wants to take in typed
information and see it on the screen simultaneously |
|
Multi-user: having more than one user, operating
systems for work stations, mainframe, mini and supercomputers allow for
more than one user |
|
|
|
|
If a single CPU is insufficient for your
computing purposes, you may need an operating system which can coordinate a
number of CPU’s (processors) |
|
asymmetric: different tasks assigned to
different CPU’s each with its own memory |
|
symmetric: tasks and memory shared equally among
CPU’s |
|
|
|
|
|
|
The operating system |
|
manages the processes |
|
manages the memory |
|
temporary storage (e.g. buffers) |
|
more permanent (e.g. disks) |
|
manages input and output |
|
manages security |
|
monitors performance |
|
|
|
|
|
An important distinction in the business life of
an operating system |
|
Proprietary: limited to a specific vendor or
computer model, marries software to specific company’s hardware |
|
Portable: will run on many different systems one
can change hardware companies without changing software companies |
|
|
|
|
MS-DOS (Microsoft Disk Operating System) |
|
Windows 3.0 and 3.1 |
|
Windows 95 |
|
Windows 98 |
|
Windows NT |
|
Windows 2000 |
|
|
|
|
Macintosh |
|
OS/2 |
|
UNIX |
|
NetWare |
|
Notes