CAT Theory
Note: highlighted definitions are the most important & should be memorized
Computer In Our Lives
Why we use computers
Efficiency
Computers save on the following:
Time – computers & computer-controlled machines can work faster than people & can
speed up time consuming tasks, as well as complete tasks in real time
Labour – reduced labour involved in mentally intensive tasks & repetitive physical tasks, as
well as perform dangerous tasks
Resources – save money by programming computers to work more efficiently with resources
and limit carbon emissions
Accuracy
Need quality programs & data to be accurate
With correct software, mass production tasks can be performed with 100% accuracy
Reliability
Perform tasks accurately, without getting tired/bored, complaining, or asking for money
Creating computerised solution is time consuming & expensive, but more cost effective in
long term
Communication
Eliminate time & distance constraints – global reach & speed means that transferring
physical goods is the only thing restricted
Communicate & share information globally – many methods, such as working on same
document, collaborative websites (Wiki) or video conferencing
Cheaper communication – VoIP makes calls for less, don’t have to pay for post, share
documents for free
Interact socially on global scale – social networks & blogs used to make friends and contacts
Types of computer systems
Factors to consider:
o How powerful – speed of CPUs, amount of RAM
o Purpose – server in network, basic office applications
o Size (mobility)
o Operating system
,Non-Portable Computers
Large & not meant to be moved around (have system, screen, mouse, keyboard)
Generally, more powerful than portable computers
All-in-one computers have system built into screen – more difficult to upgrade
Desktop computer: more common & available in different configurations
Server: powerful computer that proves resources & services to all the computers on a
network
Workstation: a computer intended for individual use that is faster & more capable than a
personal computer (intended for business/professional purposes)
Embedded systems: embedded systems, or dedicated devices, are stand-alone
electronic hardware that is designed to perform dedicated computing tasks
Entry level computer is cheapest to purchase, have low hardware specs & come with ‘home’
versions of OS / office suites
Portable Computers
Uses traditional operating systems & hardware designed for portability – all components
incorporated into a casing designed to fold (less space & protect screen)
Has a battery to allow it to be used without external power
Different types:
o Laptop/notebook: portable (run on batteries) PCs that combine the display,
keyboard, cursor positioning device & internal components into one package
Screen generally larger than 12”/13”
Can have high specs but cost more than equivalent desktop
o Tablet: portable computer w/ touch or pen sensitive screen & longer battery than
phone
Most can't make calls/SMSs, but larger screen allows for office apps or
watching videos
Smaller, cheaper & less powerful than laptops
o Hybrid computer (convertibles): reversible or detachable screen (touch or pen
sensitive) as well as normal keyboard (can be used as laptop or tablet)
o Smartphone: portable computer device that combines mobile telephone and
computing functions into one unit
Has an OS & ability to install programs
o Phablet: smartphone with screen larger than 5” (between phone & tablet – still
make calls but larger screen)
Some of these devices are always on (just in power saving mode)
Have built in cellular connection – connected permanently
Laptops are switched on then rely on Wi-Fi/cable to connect
Categories of users
Personal (Casual) Users
Do not depend on their computers for many tasks and don’t spend a lot of time using them
Use computers for: limited office tasks, banking, web browsing, social media
Entry levels computers have enough power and storage for these tasks
,Small Office Home Office (SOHO) Users
Dependent on the type of business the user runs – might need an entry level computer for
o Accounting
o Databases with clients, stock
o Electronic document archiving
o Planning and scheduling
Architects or engineers might need more powerful computer
Four main factors: mobility, battery life, screen resolution, speed
Ultrabook: small & very powerful notebooks with long battery lives – perfect for this use
case, but are very expensive
Power Users
Computing needs make use of top of the range hardware & software
Need fast processors & lots of memory/storage
May need specific hardware or software related to their interests/jobs
Will use the advanced functions of the software
More advanced users tend to use more powerful computers, but not always true
Mobile Users
Can fit into any category – just use their technology wherever they are
Laptops used for intensely productive/work related tasks
Smartphones used for: browsing internet & email, playing games, camera, GPS
Require mobility, battery life, cellular connection (sometimes)
Convergence
Convergence: the trend where separate technologies and functions that required difference devices
in the past are combined into one single device that has all or some of the functionality of each of
the separate devices (e.g. smartphones, tablets)
Data vs Information
Data: raw, unorganised number, signals, or facts (humans cannot use it effectively)
Information: facts & numbers that have been organised so that they are useful to people
Hardware Devices
Information processing cycle
Input: provides the data that needs to be processed to generate info
o Involves planning data to be captured, deciding best way to capture, creating data
capture forms
Processing: collection of steps, decisions & calculations taken to convert data into info
o Algorithm (step by step solution) to solve problems
o Involves searching, sorting, decisions, calculations
Output: proof that processing has taken place
, o Can also be stored, communicated, used as input (in same or different program or
system), or used to control other devices
Storage: where data, software & outputs are kept when the computer is not processing
them (can later become inputs)
o Involves more than hardware:
Choosing correct medium
Implementing security measures (encryption)
Implementing backup policies
Communication: allows ICT devices to connect with each other (output or input can be
communicated)
Combining input sources & output destinations
Input comes from multiple sources & output goes to multiple destinations (enhances
productivity)
Examples:
o Musician connects MIDI (musical instrument digital interface) piano keyboard to
computer via USB AND uses keyboard & mouse to create music
o When playing a game, your phone detects movement with sensors AND allows for
touch controls
o Desktop computers have many outputs (speaker, monitor, printer)
Input Devices
Keyboard
Uses: type in data, give commands
Advantages:
o Fastest way to enter text (if user can type quickly & accurately)
o Easy to use & learn
Limitations:
o Not designed to be used with GUI
o Takes up space on mobile devices (compared to on-screen keyboard)
o Difficult to use for disabled users (or with arthritis)
o Requires skill to be efficient
Ergonomic considerations
o Some keyboards position keys so that you hold your hands in a natural position to
reduce the risk of RSI (repetitive strain injury) such as carpal tunnel syndrome
o Soft-touch keys & wrist wrests can help
Wireless vs wired
o Wireless keyboard reduces desktop clutter, but can’t be used if it runs out of battery
or transmitter is damaged
Troubleshooting
o The keys are ‘sticky’: unplug the keyboard & clean with a damp cloth or brush
o Not responding:
