Transcript System software - Barbados SDA Secondary

System software
• System software is the name given to the
software that controls the hardware and
how all other software works. The most
commonly used system software, called
an operating system, is Windows, made
by the Microsoft Corporation. Without an
operating system a computer just would
not work.
Operating system
• Popular operating systems include
Windows XP, Windows NT, Windows
2000, Mac OS X, LINUX and UNIX.
Booting
• The process of starting a
computer is known as booting.
The first thing a computer does
when it is booted is to check that
it is working properly. It does this
by following certain instructions
held on a ROM chip known as the
BIOS.
• You can often see this happening
as various lines of text briefly
appear on the computer monitor.
It will then look for an operating
system (OS) to tell it what to do
next. The operating system is
loaded from disk to the
computer’s random access
memory (RAM).
Software Control
The operating system controls how all
software applications, games or other
programs work on the computer, such
as:
• file management — saving, copying,
renaming and deleting files
• multi-tasking — allowing more than
one program to run (work) at the
same time;
•for example, using a desktop
publishing program while a graphics
program is still running
• multi-user — allowing more than one
user on a computer network to
access the same file at the same time
• security — when passwords have
been set, allowing only those with the
correct password to use the
computer.
Utility software
• Utility software is specialized software
that tries to protect and maintain the
system software, just like a mechanic
maintains the smooth working of a car’s
engine when it is serviced. Examples of
the tasks undertaken by utility software
include protecting software against
damage caused by computer viruses,
making copies of files (backing up) and
recovering files after software has stopped
working (crashed).
Hardware control
• The operating system also sets the rules for
controlling hardware resources such as:
• peripherals — controlling peripheral devices
such as keyboards, printers and scanners
• memory — controlling the amount of memory
used
• CPU — controlling the time allocated to a task
by the central processing unit (CPU)
• disk space — controlling the amount of disk
space used.
QUESTIONS
• 1 Explain what is meant by: a
booting b operating system.
• 2 Give four ways each in which an
operating system
controls
hardware and software on a
computer.
• 3 List three different operating
systems used on computers.
Application software
• Note: an operating system such as Windows is essential
for a computer to work.
• Most of the software we use regularly has
been created to do specific tasks —for
example, word processing or desktop
publishing. The term for software such as
this is application software or program.
• Application software is defined as
programs that enable the computer to
carry out one or more specific tasks.
General-purpose software
• The most popular application programs
are those that are not specific to any
organisation or business and can be used
by anybody.
• The programs that you use at school or
home — word processing, databases,
spreadsheets, presentation, drawing and
painting — will be such programs.
• These programs are known as
general-purpose software, because
the user decides what to use the
software for. For example, you might
want to use a word processor to write
a letter or curriculum vitae (CV), or to
design a poster for the school play.
• General—purpose software is
much cheaper because it has
been used by millions of people
over a number of years and is
generally error (bug) free. Popular
examples of application programs
(software) are given NEXT.
Custom-written software
• Custom-written software, which is
also known as bespoke or tailormade, can modify generalpurpose software to perform
specific tasks for the user.
• Again word processing,
spreadsheet and database
programs are examples of
general purpose software that can
be custom-made by automating
certain parts of the software, or
writing and adding programming
modules to perform specific tasks.
Specialised software
• Specialised software is written solely
for a specific task.
• Examples are software used by air
traffic controllers to manage the
flights of thousands of aircraft,
accounting software, airline
reservations software and computeraided design.
• These are not general-purpose,
since the users of these kinds of
software (for example,
accountants and engineers) are
trained in a particular field of
expertise.
• Since this software is specific to
an organisation or business it can
be very costly to create.
Integrated software
• Many computers are sold with
integrated software already
installed.
• Integrated software is the term for a
program that includes all the major
types of application (for example,
word processing, spreadsheet and
database) and brings them together
into a into single software package.
• Microsoft Works is an example of
integrated software. Some
integrated software, such as
AppleWorks, also includes
presentation, drawing and
painting features, making in effect
six programs in one.
• The large software companies such
as Microsoft, Corel and Lotus, sell
their main application programs
together in one package.
• Although packages such as these are
sold as integrated software, it is not
true integrated software, as all of the
programs are still separate
applications.
There are five advantages of
integrated software
1. You get extremely good value
for money, with up to six
packages rolled into one.
2. You have to learn how to use
only one package since the user
interface is the same for choosing
commands.
3.Data can be easily transferred
from one integrated application
to another, using cut, copy and
paste.
4. It does not take up as much disk
space as separate applications.
5. It takes up less memory than
separate applications.
There are two disadvantages of
integrated software
1.Not all of the features of single
applications are included.
Therefore, the integrated software may
not be up to the task you want it for.
2. Some integrated packages do not
include all of the applications that
may be required.
NOTE
• Choosing software should be no different
from choosing any tool for a job.
• Just as in construction you decide
whether to use a screwdriver or hammer
to do a particular task, so with software
you need to decide what it is you actually
need to produce. and then choose the
most appropriate program.
• This is very important when choosing
programs to use for your coursework.
QUESTIONS
1 What is an application program? Give
three example of application programs.
2 What is the difference between general
purpose and custom-written software?
3 Give one advantage and one
disadvantage of integrated software.
4 What application software would you use
for:
a lots of calculations
b searching and sorting data
c creating an invitation?
User interfaces
• How you interact with a computer and
use it is controlled by the computer—
user interface.
• After the computer has booted up and
loaded the operating system, you will see
the user interface
• (also known as the human—computer
interface).
There are three main types of
user interface:
1.command-line interface
2.menu-driven interface
3. graphical user interface (GUI).
Command-line interfaces
• Command-line interfaces require you to
type in commands using a special
language
• This special language makes command
line interfaces difficult to use, especially for
new computer users.
• One example of a command—line
interface is the Microsoft Disk Operating
System (MS-DOS).
• In all cases, the command must be given at a
specified prompt to indicate the drive on which
the data is stored and the directory or folder in
which the file is located. For example, a
prompt which shows
• C:\> means that all commands will be
performed with data on drive C:
• A command prompt with A:\> refers to a
diskette in the disk drive. A sub-directory or
folder is similar to a drawer in which related
data items are held. Hence data may be stored
in a folder such as C:\SBA> which is on the
hard drive.
Some MS-DOS Commands
Menu-driven Interfaces
• A menu is a list of options from which you
can choose what you want to do.
Application programs use menus as an
easy alternative to having to learn program
commands.
• Menu-driven interfaces were developed to
try to make the interface friendlier and
easier to learn. You can control the
computer by choosing commands and
available options from a menu, using the
keyboard or a mouse.
Graphical User Interfaces
• Graphical user interfaces (GUIs) are
provided by the Windows and Macintosh
operating systems.
• GUIs are presently regarded as the user
interfaces which are easiest to use. As a
result, all computers are now supplied with
a GUI system installed,
• The best way to remember what makes up
a GUI is to think of the word WIMP, which
stands for Windows, Icons, Menus and
Pointers.
WINDOWS
• A window is that part of the screen
that holds its own document or
message.
• Most computers now use windowbased programs. A window can take
up the whole screen or can be
resized, moved or shrunk
(minimised).
• Each time you open a folder, you
see its contents in a new window
More than one window can be
open at the same time.
• This is particularly useful if you
want to move from one window to
another or to copy files from one
window to another.
Icons
• An icon is a tiny picture of an object
that is displayed on screen. Normally,
you can use the icon in some way.
• For example, by using the mouse to
double click on the icon of the
Microsoft Excel spreadsheet program,
you will start the program.
• Icons are designed to make things
easier for computer users. Instead of
having to remember commands, all
you have to do is to remember what
the icons look like.
• Icons are not just for programs. There
are icons for folders, the recycle bin
(wastebasket), disk drives and
printers.
Menus
• An advantage of using menus in Windows
or on a Macintosh is that, for most
programs, the first few menus are always
in the same order.
• They also carry out the same functions, no
matter which program you are using.
• For example, the file menu is first and
enables you, among other things, to
create, save and print a document.
Pull-down means
• Pull-down means (Fig 1.33) are activated
by clicking on the menu item (such as
‘File’) using the left mouse button.
• The menu pulls down just below the menu
item, and you can scroll down through the
various items. More complicated pull-down
menus can produce additional pull-down
or pop-up menus.
Pop-up menus
• Pop-up menus are activated by
clicking anywhere on the document
screen using the right mouse button.
• Some standard commands and
options are available on these menus,
including the cut, copy and paste
commands.
Pointers
• The most common pointing device is a
mouse. As the mouse is moved, a pointer
moves around the screen.
• The pointer is a very important part of a
GUI, as it enables you to control the
computer and to choose window items, to
select text in a document or cells in a
spreadsheet, and to create drawings and
shapes
• Other pointing devices include track pads,
graphics tablets, joysticks and trackballs.
Improving interfaces
• Software companies spend a great deal of
time and effort trying to improve the
interface so that the computer is easy to
use.
• An important part of this is to design the
system software and application programs
so that they work exactly the same way
each time they are used, and the menus
are always in the same place.
• People use computers for many
hours a day. Therefore, the screen
design and screen colours must be
visually pleasing and soothing. Also,
some colours might be impossible for
the visually impaired to see.
QUESTIONS
• 1 List three types of user interface.
• 2 Explain what is meant by a GUI and
WIMP. Why do you think GUIs are the
most popular user interface?
• 3 Give two important factors that should
be taken into account when designing a
user interface.
• 4 What is the difference between a popup and a pulldown menu?
File Management
Techniques
• Before you learn how to
save your work and locate
files and programs, you
need to understand the
rules of managing files and
the folders they are stored
in. This is called file
management.
• Windows Explorer is a file
management utility provided for
organizing your files on storage
devices such as diskettes, hard disk
and CD.
• Windows maintains a directory for
each disk, CD-ROM and drive, which
provides a list of the filenames, type
of files, date and time the files were
created and the file size.
• Windows explorer can be
opened in Microsoft Windows
XP, for example, through the
Start, Programs, Accessories
menu.
Managing files
Here are some basic terms
you should know:
• File: Every document that you
use is called a file. So, the
program that is used to start an
application, or the document you
typed, are both called files.
Folder: Just
as you would have a
folder to keep notes or documents
together, files are grouped
together in folders (also called
directories).The icon for a folder
on the computer screen looks
quite like a typical folder.
• Drive:Your computer
may have
many storage devices such as the
hard drive, floppy drive, USB
drive or CD drive. These devices
contain the files and folders that
you work with. Each drive is given
a specific drive letter to
distinguish it from the other
drives.
• For example, the floppy drive is
usually called drive A. If there is
another floppy drive then it is
called drive B. The hard drive is
called drive C and so on. Network
drives are usually further down
the alphabet. like M or 0.
• Path: To
locate a file, you may
have to select the drive and then
one or more folders, This
sequence to get to the specific
folder or file is called the path.
Since you must first select the
drive, a path always starts with a
drive letter.
• Also, since it is a file or folder you
are looking for, that file or folder
name is the last in the path. for
example, C:\CXC\Unitl.doc
means that the file Uniti .doc is
found in the CXC folder located
• on drive C. The backslash \ is
used to separate the file, folder or
drive name.
File names
• How do you choose a name for your
file? A file name has two parts:
FILENAME and EXTENSION. When
you look at file names on the
computer, they may look like
filename.ext.
• In the past, file names had to have I
to 8 characters in the FILENAME and
0 to 3 in the
• EXTENSION. Sometimes you
may just see the filename since
the extension may be hidden.
Most programs have a default
extension which they will assign
to files that they save unless you
specifically type in something
different.
• You can create your own method for
naming files based on the date, the type of
document, the project it’s about, or
whatever coding scheme you want. It may
look confusing to others, but it is only
important that you know what your file
names mean. Just remember that what is
obvious today may be obscure next week!
Generally it is best to keep the filenames
as simple and direct as possible.
• Extensions are associated with specific
programs. For example, ‘cxc’ shows that the file
is an executable, meaning that it starts a
program or application. Here are some more
examples:
• device.com — command file
• autoexec.bat — batch file
• uniti .doc — word processing file
• intro.txt — text file (similar to word processing
file)
• index.htm — hypertext document for the
Internet.
• config.sys — system file
• A file name such as ‘Report to
President for 2004.doc.’is called a
long file name, meaning that it is
longer than 8 characters plus 3 for the
extension. It also contains spaces.
These are legal and acceptable under
Windows 93/98/XP and some other
operating systems.
• Certain characters cannot be
used in file names. They are
reserved by the operating system
for special uses.
• The characters: . , / \ : ; [ ] “|= are
all illegal in a file name.
User back-up
• Besides protecting the physical medium
you are using to store data, you must also
consider what you can do to safeguard the
data itself.
• If the disk is kept from physical harm, but
the data gets erased, you still have a
major problem. So what can you do to
safeguard the data on which you rely?
Write protect
• This keeps your files from being
overwritten with new data. For diskettes,
you do this physically, by opening the
write-protect slide so that you can see
through the hole.
Make copies
• Make multiple copies on other diskettes.
The more important the files are, the more
copies in more secure places you need.
Data Processing
• Data must be processed by the most
suitable means. It can then be transferred
to one or more computer systems for more
processing, for output or for storage.
• This processing can be achieved by three
methods:
• batch processing
• on-line processing
• real—time processing
Batch processing
• A batch processing system is one where
data is collected together in a batch before
processing starts. With early computers
data was entered on punched cards (or
Hollerith cards), which were handled in
batches, hence the term batch processing.
• Batch processing is most suitable for tasks
where a large amount of data has to be
processed on a regular basis. When a
batch job begins, it will continue until it is
completed, or until an error occurs.
• Examples of batch processing systems
include those that process utility bills such
as water and electricity, payroll systems
and examination report card systems.
• Credit card companies also process billing
in batches. The customer does not receive
a bill for each separate credit card
purchase but one monthly bill for all of that
month’s purchases.
• The bill is created through batch
processing, where all the data is collected
and held until the bill is processed as a
batch at the end of the billing cycle.
Advantages
• Once the data is submitted for
processing, the computer may be left
running without human interaction.
• The computer is only used for a
certain period of time for the batch
job.
• Jobs can be scheduled for a time
when the computer is not busy.
Disadvantages
•
There is always a delay before
work is processed and returned
since batch jobs are usually
stored up over a period of time.
• It usually involves an expensive
computer and a large number of
trained staff.
On-line and real-time processing
• Computers and peripheral devices are
on-line when they are connected to a
main processor and turned on, so that
the operator can interact with them.
• Examples of on—line processing
include devices such are printers
which are on—line when they are
ready to receive data from the
computer to print.
• Most printers have an online
button you can press to turn the
machine on. If it is turned off then
you are off-line. You can also be
on-line if you are connected to,
say, the Internet through a
modem or network.
• A real—time processing system
processes data without significant
delay, making it always up-to-date.
Since processing must be connected
to one or more computers to process
data, then it must also be on-line.
However. note that on-line does not
necessarily imply that processing is
real-time since there may be some
delay with an on-line system.
• Examples of real-time processing
systems include anti-missile
defense systems, airplane landing
control system, flight simulation
systems, electronic fund transfer
systems and ticket reservation
systems.
Advantages
•
No significant delay for response.
• Information is always up-to-date.
• Output from the computer may be
used to adjust and improve the
input back to the system.
Disadvantages
•
The computer must be dedicated
solely to the task.
• The computer must be continually
on-line.
Data Transfer
• Data transfer is the movement of
information from one place to another.
With computers this happens in three
ways:
• within a single computer
• between a computer and other
computers
• between a computer and external
devices.
Within a computer
• The loading of the operating system
when the computer is started is one
example of data being transferred
within a computer.
• The operating system data is
transferred from hard disk to the
computer’s memory (RAM).
• Data is also frequently transferred
between software applications on
a stand-alone computer.
• This can be done simply by
copying and pasting or by the
software itself opening or
importing files that were created
by a different software package.
• Importing is the term for
transferring data from one
program to another.
• For example, Microsoft Word will
open web pages and documents
created in other word-processing
packages such as Word Perfect.
Between Computers
• Most computer users will, at some time or
another, need to transfer files between
computers. School students may need to
transfer their work from a computer at home
to the school network via a diskette or a Zip
disk.
• Updates to software packages, such as
Microsoft Office, can be downloaded from the
Internet using file transfer protocol (FTP).
• Sometimes, however, transferring
data between computers requires
a little preparation as not
everybody uses the same
software. For example, one
person might use Microsoft
Access as a database, whereas
another might use Lotus
Approach.
• The solution to this is to convert the file
into a common file format that can be read
by all software packages without changing
or damaging the data.
• This process is known as file conversion.
In the example (next slide), converting the
file to CSV (comma separated values)
would enable it to be read by other
spreadsheets or databases.
Saving an Excel spreadsheet in CSV format
means that other spreadsheet or database
programs can open the file
• Text, too, can easily be converted.
Saving text in ASCII (American
Standard Code for Information
Interchange) format converts letters
into binary code that can be read by
any computer.
• There is a drawback, however,
because saving a file as ASCII resuls
in all formatting (bold, italic, etc.)
being lost.
• To overcome this problem, files can be
converted instead to Rich Text Format
(RTE).
• RTF enables the file to be opened by other
programs even those on computers
running different operating systems as
well as preserving all formatting.
• Another way of transferring data, made
popular by the Internet, is by HTML
(Hypertext Markup Language).
• Before transferring data, it is also
sometimes necessary to reduce the file
size. The process of reducing the size of a
file for storage, or for sending via the
Internet, is known as file compression.
• WinZip and Stuffit are popular programs
for compressing files. File compression is
important because some files, particularly
picture, so video and animation files, can
take up a large amount disk storage
space.
• The larger the file size, the longer it
takes to send via the Internet. This
can mean that more money is spent
on telephone calls.
• Users of the Internet will also know
that web pages containing pictures
can take a long time to load.
• Web designers try to get around this
problem by reducing the file size of
pictures -usually by saving them in
JPEG (Joint Photographic Experts
Group) format.
• When video is to be shown, this will
be compressed using the MPEG
(Moving Pictures Experts Group)
format. Music will be compressed
using MP3
QUESTIONS
• 1 List three ways in which a computer
transfers information.
• 2 Explain what is meant by the terms file
conversion and file compression.
• 3 Give one reason why many users need
to convert files.
• 4 Give two reasons why you might want
to use compressed files if you have a
modem and access to the Internet.