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Module 6 - Michaelston Community College

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					Module 6 – Software
Michaelston Community College

                              Operating System

             An operating system is software which controls the general
             operation of a computer.
             An operating system

                  controls the loading
      ...and running of programs (interpreting and executing each command)
      controls the use of peripherals such as disc drives and printers
      organises the use of the computer’s memory.
      handles interrupts (signals from devices)
      maintains security (passwords etc)


Part of the operating system is stored on a ROM chip.
When the computer is switched on, the first thing that
happens is that part of the operating system is loaded into
memory. This process is called booting up.

A computer cannot work without an operating system.

Examples of Operating Systems :
UNIX
Linux
Windows
MS-DOS

Software may be specific to a particular operating system and would therefore
not work under a different operating system.

Exercise : Operating Systems

An operating system is a ………………………….… without which a computer
cannot work.

The operating system...

maximises the use of the computer's……………………………
loads and runs other ………………………………..
handles inputs and outputs from the ………………………………….
handles …………………………… - signals from devices in need of attention
maintains the …………………………… - passwords etc
Booting up is the process of loading the operating system into memory.




Mr G. E. Parsons                                                 Page 1 of 9
Module 6 – Software
Michaelston Community College

                               Batch Processing

A batch processing system is one where programs and data are collected
together in a batch before processing starts.
Each piece of work for a batch processing system is called a job. A job usually
consists of a program and the data to be run.

Jobs are stored in job queues until the computer is ready to process them.

There is no interaction between the user and the computer while the program
is being run. Computers which do batch processing often operate at night.

Example : Payroll - when a company calculates the wages for its workforce
and prints payslips.

Exercise : Batch Processing

In a batch processing system a number of ……………………… are collected,
stored and then all run together.

There is no user ……………………………………… when the jobs are run,
and it is usually done at great …………………………… e.g. at night.

Example : Payroll system - A large business may run the wages program for
all its employees at the end of every month.

                      Multiprogramming / Multitasking

Multiprogramming is a method of running several different programs in a
computer apparently at the same time.

Usually on a mainframe - the computer has a number of programs loaded into
memory and the operating system switches quickly between them, processing
a little bit of each one in turn. The high speed of the processor makes it seem
like more than one program is being run at the same
time.

On a PC it is usually called multitasking.

Exercise : Multiprogramming
A number of ………………………………… are loaded
into memory.

Each program in turn is run for a small amount of ………………………….
time.

The ……………………………………… of the processor gives the illusion of
running more than one program at the same time.




Mr G. E. Parsons                                                   Page 2 of 9
Module 6 – Software
Michaelston Community College

                                  Multi-access

In a multi-access system a number of users have terminals (workstations)
which are directly linked to a central computer.
Each user can use the computer interactively.

Often called a multi-user system.

Each user in turn gets a small amount of processing time. The speed of the
processor gives the illusion that the user is the only one using the computer.

This would be an example of on-line processing
where the users interact directly with the
computer.




                            Distributed Systems

In a distributed system, computers and peripherals are linked together. Each
user is not aware of which computer or peripheral he / she is using.
A user on one computer may be running a program stored on another
computer accessing data stored on yet another computer.

The operating system will control access to the resources.

Exercise : Distributed Systems.

The resources of a computer system (programs, data, peripherals etc) are
found on a number of ………………………….. computers. The
………………………………………..controls access to these.

A user on computer A may be running a program stored on computer B which
accesses data stored on computer C which is then printed on a printer
connected to computer D - but it appears to the user that
…………………………………….




Mr G. E. Parsons                                                    Page 3 of 9
Module 6 – Software
Michaelston Community College

                             Real-time (Process)

Real-time means that data is processed immediately.
A real-time system is always 'up-to-date'.

The computer used in a real-time system is 'dedicated' - it does nothing else.

An example of a real-time system is a Process-Control System. Input data
received from sensors is processed immediately, analysed and any necessary
actions taken without any delay.


An example would be at a nuclear power plant.




                           Real-time (Transaction)

Another type of real-time system involves transactions. As soon as a
transaction is received by the computer, it is processed and any data files are
updated.

Example : Theatre Booking System.

The system is real-time. If a customer books a seat at a performance then the
details are added to the bookings file immediately and that seat is flagged as
'Reserved'.

Another customer who asks a few seconds later for a seat at the same
performance will not be able to book the same seat.




Mr G. E. Parsons                                                    Page 4 of 9
Module 6 – Software
Michaelston Community College

                             Parallel Processing

Some large computers may have more than one processor.
In parallel processing systems, tasks are shared between a number of
processors. The operating system allocates instructions to each processor.

The more processors that are allocated to a task - the faster that task will be
completed.

Exercise : Parallel Processing

The ………………………………….may allocate tasks to a number of
…………………………….. in a large computer.
Tasks will be completed ………………………

                                  Interactive

Interactive computing involves two-way communication between a user and a
computer - a bit like a conversation. The prompts of the computer are
responded to by inputs from the user.

Most applications run on microcomputers are interactive.

Interactive processing examples :

Word processing
Computer game
Entering data in a database
A simple example of interactive computing :
The user requests to save a file - the computer asks where to save it - the
user enters the folder - the computer asks - 'Are you sure?' - the user clicks
'Yes' etc...

Exercise : Interactive

In interactive processing the computer responds to the user's
…………………… and the user responds to the computer's …………………

Example of Interactive Processing :…………………………………….




Mr G. E. Parsons                                                     Page 5 of 9
Module 6 – Software
Michaelston Community College

                              System Security

A microcomputer is easy to keep secure. Measures may include...
locking the computer room / alarms
locking the computer
password
When a number of computers are linked (eg multi-access, network or Internet)
the security is harder to maintain.

A hacker is a person who gains unauthorised access to a computer over a
network.
Security measures may include...

each user should be given a user name and a password.
computer usage may be logged.
computers should be disconnected from a network when not in use.
call-back system. When a remote user logs in to a computer, the connection
is immediately broken and the computer dials up the user's telephone
number.
use a firewall - a computer running software which detects hackers dialing in
to a network.

Exercise : System Security

Someone who gains unauthorised access to a computer over a network is
called a ……………………………………

Measures to prevent hackers include:

each user of a system has to log in with a user name and ……………………

the computer keeps a ……………………………….of all its users

computers should be ………………………………. when not in use.

a call-back system may dial back each user when they …………………………

use special hacker-detecting software - a ………………………………..




Mr G. E. Parsons                                                  Page 6 of 9
Module 6 – Software
Michaelston Community College

                       HCI (Human Computer Interface)

The Human Computer Interface (HCI) is the way the user interacts with the
computer.

The four main types are :

Command:
The user types in commands.
Programs use less memory.
Example : The MS-DOS interface.
Type DIR /W to get a list of all the files in a directory.

Quick to operate and very flexible, but the user needs to learn all the
commands and type them in correctly.

Menu:
Drop-down menus have options for selection. There may be sub-menus...
The user selects an option with either a key or a click of the mouse.

No need to learn the commands but it can be difficult to locate a particular
option.

GUI:
Graphical User Interface
Also known as a WIMP (Windows, Icons, Menus, Pointers) interface.

Icons (small pictures) represent options. Colour and sound may also be used
to make the interface more 'user-friendly'.

Identical icons may be used in a number of different programs. Eg a picture of
a disk to save a file.

Example : Windows

Low-level IT skills needed by the user. Easy to use intuitive interface.

Sound:
Speech driven interfaces are also now available. The user talks a command
into a microphone.
Useful for...handicapped, fighter pilots, surgeons..




Mr G. E. Parsons                                                     Page 7 of 9
Module 6 – Software
Michaelston Community College
When a new computer application is being designed, decisions about which
user interface is to be used are often governed by the IT skills of the user.
Experts can use a command driven interface, but those with low IT skills will
need a GUI. Children need plenty of colour and sound.

All good Interfaces will have allow users to seek help if they need it.


Consistency of design of interfaces is important.
E.g. The same buttons are used on a GUI for printing in each application and
they appear in the same position on each display. This will make it easier for
the user to learn to use the program

Exercise : User Interface

The way in which a user interacts with a computer is called the
…………………………

The four main types are :

Command-driven - The user types in commands
- commands must be learned and typed correctly
- flexible ie lots of options
- fast (uses less memory)

Menu-driven - there are drop-down menus to select options from.
- easy to use
- may be difficult to find options

GUI - …………………………….
- also known as WIMP …………………………..
- intuitive and easy-to-use
- ……………………-level IT skills needed
- uses a lot of memory so slower to operate.

Sound - the user speaks commands into a microphone.
- useful for handicapped and e.g. drivers, pilots, surgeons.




Mr G. E. Parsons                                                      Page 8 of 9
Module 6 – Software
Michaelston Community College

                            Systems Analysis
The stages of systems analysis (often called the system life cycle) are:

Analysis:
a preliminary study to decide exactly what the problem is.
undertake a feasibility study - an investigation into whether a new system is
realistic.
study of present system - collection of data, interview staff...

Design:
design hardware, software specifications, data storage and methods. Design
of security methods.
top-down design involves repeatedly breaking down the design into smaller
and smaller parts.
evaluation criteria must be specified. These are the standards by which the
success of the new system will be measured.

Development and testing:
write new programs, prepare documentation.
devise a test plan which involves normal data, extreme data, invalid data and
null data.
test and debug the system.

Implementation:
convert to new system, install hardware and software, train staff.

Maintenance:
monitor system and solve problems as they arise. Keeping documentation up-
to-date. There may slight adjustments to make as the business changes.

Exercise : Systems Analysis

When a computer system needs to be installed or updated a systems analyst
is called in.

A - …………………………….- a study of the problem (interviews,
questionnaires, observation and reading existing documentation). Doing a
feasibility study.

D - ……………………………….. - designing data storage, hardware and
software requirements.

D - ………………………………… - writing and testing new programs,
preparing documentation

I - ………………………………… - switching over to the new system, installing
hardware and software, training the staff.

M - …………………………………. - monitoring the system and solving
problems as they arise.


Mr G. E. Parsons                                                     Page 9 of 9

				
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