Computer Aided Design :

Computer Aided Design also known as CAD for short.

- Computer Aided Design is the use of the computer to design objects for production or manufacture, such as houses, cars, boats and electronic circuits.

- CAD allows professionals such as engineers and draftsmen to produce complex drawings quickly and easily.
FEATURES :

1. CAD provides interactive drawing tools which means there is immediate response to input direct communication between users and computers.

2. CAD provides 2-D, 3-D and even (12, 14, 16-D) dimensional drawings.

3. A scale model allows user to see any angle from any different view.

ADVANTAGE OF USING CAD :
1) CAD save time.

2) A figure can be easily rotated, modified, copied, scaled (enlarged or reduced) and reflected.

3) CAD generated drawings are far better than manual drawings.

4) It is possible to present the drawing from different angles and in different sizes without redrawing.
APPLICATION OF CAD :
1) Building models : car, earoplane and goods manufacturers use CAD extensively to build 2-D or 3-D models.

2) Computer Aided Manufacturing : a computer directs the machines to make a products. The product to be made would have to be designed by using a CAD program. Both CAD and CAM are automating the manufacturing process. by using both application, its make production cheaper.

advantages and disadvantages of the written and off-shelf software :

advantages for the Written / Custom software :

1. You have the whole right to the software as it was created for you.
2. The software can be edited over and over again if there were problems arises.
3. The software can also be used to combined the features from other packages with the features that the company needs.
4. Not to forget, it is very expensive to in term of prices.


disadvantages for the Written / Custom software :

1. It is actually expensive to hire programmers to design the software.
2. the programmers must have a very good skill and expert to fulfill the company needs.
3. it also takes a lot of time to finish the software.

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advantages for the Off-Shelf software :

1. It is suitable for everybody to use the software.
2. Their documentation is easy to undersatnd and it is tested before being sold. So the software is user friendly and easy to use.
3. It is cheaper since no need to hire any programmers.


disadvantages for the Off-Shelf software :

1. The software doesn't meet the organization/business need exactly.

difference between written and off-shelf software :

Written / Custom Software :
It is specially made by the skillful and expert programmers that is specifically written for the purpose to carry out or to perform the required task that is fulfill the organization needs or individual..

Off-Shelf Software :

this is the ready-made software which can be easily found at every computer shop.

TOPIC 4 :

** application softwares **

the differences between written software and off-the-shelf software

e) the purpose of a range of utility software :

1) disk formatting: to divide up the surface of a disk into more easily manageable sectors.

2) file handling: to manage the files that are stored on a computer software system

3) virus checkers: used to check any files on or entering the system for viruses. They scan all files in different locations and the content of the memory, also unexpected program behaviour. and anywhere else where it is relevant for the intention of identifying/removing maleware (malware is the generic category of any programs that perform a negative effect on your computer without your knowledge or permission). This utility purpose is so that all files are protected from viruses and keeping them safe so they aren't damaged by viruses entering the system.

4) File compression: the system utility programs convert data into a format that takes up far less memory space, enabling faster communications. Compression software is particularly useful when data is being sent from one computer to another.

d) Natural language :

Natural language Interfaces are designed for understands human speech and to give prompts and responses in natural language.

This should be the easiest type of interface for any of us to use and shouldn’t require too much training.

However, it has some problems where :
the processing is quite intensive and this can make the software slow, Regional accents means that many people say the same words in very different ways, People use different phrases to mean the same thing, so it’s hard for the software to understand everything and also People often don’t like the sound of computerized speech.

d) Command-line :

Command-line Interface can be powerful and fast as it consist of simple prompt screen into which the user types commands for the computer to carry out.

A good example is MS-DOS.This kind of system can be very quick and flexible if you know what you’re doing. It’s good for the computer programmers and other IT specialists who really understand how the system works.

d) Graphical User Interface :

Graphical User Interface are great for beginners.
- This is because Graphical User Interfaces tend to be intuitive. This means that once you know about buttons, scroll bars and other controls, you can generally guess what you need to do next.

- There is often context sensitive help, and the interface will be designed to make it as easy as possible for the user to enter data.

- Because all of the features added to make the GUI easy to use, the actual software can sometimes be quite slow as processing time is taken up by the interface.

- Also, in order not to confuse the user with too much information, many commands are hidden and must be found by sing help manuals.

d) menus and forms :

Menus : are commonly used in Graphical User Interface, Operataing system and allow a user to quickly access various options the software program is capable of performing. File menus are commonly accessed using the computer mouse; however, may also sometimes be accessed usin shortcuts and/or the keyboard.

- Pop-up menu :
a menu that is not visible until accessed. When accessed, this menu will open a new window and commonly be above all other screens on the display.

- Full Screen Menu :
this type of menu is often used as the 'front end' of an application. It stays on screen until the user makes a choice.

- Pull-Down Menu :

this type of menu is displayed along the top of the screen, and when the user clicks on an item, a sub-menu appears. The menu is always present whatever screen the user is looking at in the application.

Forms : it is usually an official document with questions n it and spaces where you give answers and personal informations.

c) a range appliation that need a real time response :

Computer controlled servomechanisms (device used to correct the performance of a mechanism automatically, by means of error-sensing feedback) for heat or other environmental maintenance; medical diagnostic and or exam technologies like MRI's, echocardiograms, etc, doppler weather monitoring, air traffic control systems, some computerized communications technology...

( http://wiki.answers.com/Q/Example_of_real_time_processing)

c) a range of applications requiring batch processing :

An example of batch processing is the way that credit card companies process billing. 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 of the data are collected and held until the bill is processed as a batch at the end of the billing cycle.

b) Network System :

-> Definition of network : computers linked together allowing resources to be shared and data to be transfered.

* most computers nowadays are linked together in network, either to other computers in a building (LAN), or to computers around the world (WAN).

* this allows hardware and software to be shared and users to communicate with each other.

example ;

- computers in schoolare networked so that any user can log on at any machine.

learn the right terms of to talk about linking networks :

1) a bridge can be used to link wo similar LANs together.

2) a gateway/router is used to link together two different networks - e.g. connecting LAN to a WAN.

3) a repeater is used to boost (amplify) the signal on a LAN which covers a long distance.

The two major types of network operating systems are :

1) peer-to-peer : this is when a small number of computers are linked and can communicate but there is no central file server. it is easy and straightforward to set up and the software to do so is often contained in teh operating system.

2) client-server : this is where there is main server that controls the network. the computers linked to it are called clients, hence the name client-server network. It requires specialised softwar running on the server and is needed when there is a reasonably large number of users (say over 10).

b) Multi-tasking :

• * Because lots of programs need to be run at once (especially in a Windows environment), operating system need to be able to multi-task.
  
• * Multi-tasking makes it appear as if multiple programs are running simultaneously, but actually that’s just an illusion caused by the fast processing speed of the CPU.
  
• * What actually happens is that the CPU divides its time between various tasks – it performs part of the task on one application, followed by part of a task on another application. It then returns to the first application, and so on..

b) Single-user and Multi-user System :

Single user system is the name given to operating systems where one user has access at a time. These are the familiar operating systems usually associated with PCs.

Multi-user system allow more than one user to access and use the computer at the same time. This can be seen in Local Area Networks (LANS), with computer servers that are accessed by multiple users.

b) real-time processing :

real-time is a term used to describe a process or event that occurs immediately.
For example, chat program occur in real-time, where messages are seen immediately after the user presses his or her enter key

real-time operating system :

For example:
In a bank transaction, Bob tried to deposit money to his account.

In REAL TIME, the money is DEPOSITED right away as soon as Bob handed the money.. and there's no turning back! :)

b) batch processing :

(1) Performing a particular operation automatically on a group (batch) of files all at once rather than manually opening, editing and saving one file at a time is called batch processing.
- For example, graphics software that converts a selection of images from one format to another would be a batch processing utility.

(2) batch processing is when processing a group of transactions at one time. Transactions are collected and processed against the master files (master files updated) at the end of the day or some other time period.
http://encyclopedia2.thefreedictionary.com/batch+processing

A better example would be :
if you try to deposit money to a foreign account (bank account in another country), the bank would just put your request in queue with all the other inter-bank/country requests and process them at the end of the day or when they reach a certain amount.

a) the purpose of an operating system

• An operating system is a software program that enables the computer hardware to communicate and operate with the computer software. Without a computer operating system, a computer and software programs would be useless.

** OS is a software that manages the computer hardware and enables the applications software and the rest of computer to run and to do work.


Linu, Unix, windows xp, windows vista, MacOS are all examples of operating systems :

TOPIC 2

** SYSTEM SOFTWARE **

(operating system, user interfaces, utility software)