Computer studies Chapter 1-4

What is a computer?

A computer is an electronic machine which accepts input such as numbers, text, sound, images and video; and under a stored program

Data

Is raw unprocessed facts

information

Data converted into a meaningful and useful context

The four basic functions of a computer

input process output storage

Binary Code

The most basic language a computer understands, it is composed of a series of 0s and 1s. The computer interprets the code to form numbers, letters, punctuation marks, and symbols.

First Generation Of Computers (1940-1956)

The computers of the first generation used vacuum tubes as the basic components for memory and circuitry for the CPU

They produced a lot of heat

They were very expensive

They used punch cards for input and printouts for output They used magnetic drums for memory

Second Generations Of Computers (1956-1963)

Use of transistors

Reliable in comparison to first-generation computers

Smaller size as compared to first-generation computers

Generated less heat as compared to first-generation computers

Consumed less electricity as compared to first-generation computers

Magnetic cores and disks were used for memory

Third Generation Of Computers( 1964-1971)

The computers of third generation used Integrated Circuits (ICs) in place of transistors

More reliable in comparison to previous two generations

Smaller size

Generated less heat

Faster

Consumed lesser electricity

Fourth Generation Of Computers (1971-1980)

Very cheap

Portable and reliable

Very small size

The concept of internet was introduced

Computers became easily available

Classification of Computers

Supercomputer

• Most powerful computers in terms of performance and data processing, have high speed

• Very expensive and used for specialized applications that require massive amounts of mathematical calculations

• Very large in size and accommodated in large air-conditioned room, some take up whole building

• Used for research purposes, weather forecasting, census counting, designing aircraft and so forth

Mainframe

• Computers designed to handle very high volume input and output (I/O) and are more on throughput computing.

• Vary in sizes from small to large according to what they are used for • Generally they are very large and expensive and capable of supporting hundreds, or even thousands, of users at the same time

• Uses its power to execute many programs at the same time

• Used by large organizations such as insurance companies, banks and airlines to process millions of transaction

Microcomputers

• Small and is based on microprocessor technology

• Also known as a personal computer meant to support one person and can also be connected to a network system.

• Cheap

• Used for word processing, accounting, desktop publishing and other applications

• Also used at home for playing games, surfing the internet and watching movies

• Examples are: desktop model, tower model, laptops, netbooks and Personal Digital Assistants (PDA)

• Desktop Model

• Designed to fit comfortably on top of a desk, typically with the monitor sitting on top of the case and a keyboard in front of the case.

• Tower Model

• Microcomputer whose case is ideally placed on the floor beside a desk.

• You only see the keyboard, mouse and monitor on top of the desk.

• Tower models are narrow and tall whereas desktop models are broad and low

Laptop Computer

• Small, lightweight portable computer small enough to sit on your laps.

• Has built in monitor, keyboard, hard disk drive, battery and touch pad which work as a mouse

• They are also known as notebook computers

Netbook computer

• Also small and lightweight, low-power notebook computer that has less processing power than a full-sized laptop.

• Designed for basic tasks like word processing, web searching and emails.

• Other names include subnotebook, ultra-portable, mini-notebook etc.

Personal Digital Assistants (PDA)

• A handheld computer that combines personal organization tools with the ability in some cases to send e-mail and faxes

• Uses a touchpad and removable keyboard and sometimes a voice recorder

• Used as personal information recorder to record telephone numbers, addresses, appointments and to do lists

• Can connect with other microcomputers to send e-mails, text documents and other files.

Workstations

• A computer used for complex scientific, mathematical, engineering calculations and for computer aided design (CAD) or Computer Aided Manufacturing (CAM) and other types of applications that requires enough amount of computing power and relatively high quality graphics capability.

• Expensive as they come with large and high-resolution graphics screen

• Have large amount of RAM

• Built-in network support and a graphical user interface

Microcontroller

• Small and low cost computers built for the purpose of dealing with specific tasks.

• Used in products that require a degree of control to be applied by the user.

• Used in products like digital cameras to take and store pictures, play-stations, washing machines, TV, microwave to store data about the time needed to warm food and also in other products.

Servers

• A central computer that stores data and programs that can be shared to personal computers, workstations and other devices like printers.

• They store files, make printing stations available, transmit emails, store financial records and more

• Banks use severs to store financial records

• MTC uses servers to store people’s phone records and transmit calls

computer lab

A computer laboratory is a room which is meant to give services to a certain community

Safety Precautions

 Should contain physical security and a person in charge all the times

 Use Uninterrupted Power Supplies (UPS) in cases where electricity goes on/off all the times

 Ventilation in the lab is required to avoid overheating of computers

 Moisture or wet environment is not recommended in the lab so avoid bringing food and water

 Make use of ergonomics to avoid body injury

Classes of hardware

Hardware is divided into two major classes, called peripherals and central processing unit

peripherals

Additional components besides the main parts of the computer such as printers and scanners.

Input Devices - definition

Are the equipment used by the user to enter requests

Output devices

Devices the computer uses to communicate the results of a process to the user(ex: monitor

External storage devices

Are the equipment which stores the the output permanently for future use or reference

keyboard

An input device that enters data with letters

types of keyboards

standard

Parts of a mouse

The left mouse button is used most frequently and it's function is to select items

right click provides an easy access menu in programs and within the operating system

mouse

an input device that allows a user to control a small symbol on the screen called a pointer

pointing devices

Mouse, trackball, touchpad, pointing stick, joystick, light pen and digitizer

optical scanner

Are light sensing input devices that read printed text and graphics

Types of scanners

• Flatbed

  • they work as photocopying machines

• Sheet-fed

  • to scam an item with this machine it has to be put into a station scanning head

• Handheld

  • the pen is moved by hand over text or graphics being scanned.

• Drum

  • the item to be scanned rotates on the drum scanning mechanism which is a glass cylinder having sensors inside that convert light signals into digital signals

Card reader

a data input device that reads data stored on cards and is entered into the computer

Applications of card readers

\-Banking; to read bank cards.
\-Payments for purchase at point of sale through electronic funds transfer.
\-Security purposes; positive identification is required in some places where a card has to be used to allow access

* Pre-paid payments are also done using cards
* Payment for public transport is also done using cards

barcode reader

An input device used to capture and read information stored on a barcode

biometric scanner

scans a human physical attribute, like a fingerprint or iris, for security purposes

Radio Frequency Identification (RFID)

Is a system that uses radio signals to communicate with a unique serial number fixed on an object

Optical Mark Recognition (OMR)

Input devices that reads simple multiple-choice style answers by looking for marks on the paper.

Optical Character Recognition (OCR)

Technology that can translate a scanned document image into text that can be edited and formatted.

speech recognition

The process by which computers recognize voice patterns and words

digital camera

Is a mobile device that is used to take stil or video pictures and store them digitally on its hard disk or a memory card

webcam

Is a small digital movie camera attached on a computer to record moving images that can be sent to a website in real time

Video calling and conferencing

Video calls differ from video conferencing in that video call is for point-to-point calls between two units and video conferencing allows people two or more separate geographical locations to communicate

video security

Webcams are also used as security cameras.with the associated software

Sensors

Is an input device that detects events or changes in its environment and directly transmits data to the computer

The four components of a Cpu

1. The control unit
2. Arithmetic Logic Unit (ALU)
3. Memory

4. Processors

Types of processors

Multi-core processor – has two or more separate processor cores.

Dual core processor – has two separate processor cores.

Quad core possessor – has four separate processor cores.

There are four type of memory

a. Primary memory

b. Secondary memory

c. virtual memory

Primary Storage

• Primary memory is also known as main memory

a. Example

• RAM – Random Access Memory

• ROM – Read Only Memory

• Cache

RAM

There are two types of RAM:

 DRAM (Dynamic Random Access Memory)

 SRAM (Static Random Access Memory)

Secondary storage devices

• It is not directly accessible by the CPU Example of secondary storage devices

1\. Hard disk

2\. Floppy Disk

Zip diskette

USB Flash drive

5\. Memory card

Properties of storage Medias

• Volatile and non-volatile

Volatile memory

• Requires constant power to maintain the stored information.

• The fastest memory technologies.

• All contents are erased when the system's power is turned off or interrupted.

• It has been more popularly known as temporary memory.

Non-Volatile Memory

• Device which keeps the data even when the power is off. • It is suitable for long-term storage of information.

Hard disk

A hard disc is a thin but rigid metal, glass, or ceramic covered with a materials that allows data to be held in the form of magnetized dots

Solid State Storage (SSS)

SSS is a type of non-volatile computer storage that stores and retrieves digital data only using electrical circuits, with out the involvement of any mechanical moving parts

Flash Memory

Flash memory is a non-volatile but the data stored in it can be erased electronically

Characteristics of SSS

SSD is much faster than hard disk

SSD use less power and produce less heat

SSD’s lifespan is longer than that of a hard disk

Smart cards

A smart card is a plastic card that has a built-in microprocessor and chips

Smarts cards can be:

Contact

Contactless

Optical

Optical disks

Are removable optical disks which use laser technology to record and read data

Types of CD’s

CD-ROM: Are only read disks

CD-R: Comes black and allows the user to record on it

CD-RW: Allows the user to record and erase data

Types of DVD’s

DVD-ROM: Comes with pre-recorded information

DVD-R: It is a write once read many times disk

DVD-RW: Comes blank and allows the user to both read and write on it over and over again

Types of Blue-ray discs

BD-ROM: Have capacities of 100 gb they are read only

BD-D: Can be written on once and read many times

BD-RW: can be written on and read many times

Rules for maintenance of optical discs

Hold by the edge of the edge of the CD

Store the disk in a case to avoid scratches

Store the disc in a cool, dry environment

Do not touch the recording surface or place it on a flat surface

Backup

Backup is a copy of the original which is kept incase the original is lost or damaged

Cache memory

is a type of memory used to hold frequently used data

Virtual memory

is a technique of on OS that allows some free disk storage to be used to extend the capacity of RAM

Cloud Storage

is an internet service that provides virtual pools of data storage to computer users

Why do people subscribe to cloud?

To access their files over the internet from any computer or devices connected to the internet

To avoid downloading large audio. video and graphics files onto other storage devices

To store backups

To allows other people to access their files from anywhere

Soft copy VS Hard copy

Soft copy devices

 Device that gives electronic display of digital information

. Example of soft copy devices

 Monitors/screens

 Audio outputs

 Projecting devices

 Light emitting diodes

\
 A hard copy is a printed copy of information from a computer.

Example of hard copy devices – printer and plotters

Printers can be categorized into:

 Impact Printer

 Non-Impact Printer

Two types of Monitors

LCD Monitors

LED Monitors

Projectors

A data projector is an electronic device that projects computer output onto a white or silver fabric screen

Impact printers

It strikes paper and ribbon together to form a character, like a typewriter.

 Creates characters by striking pins against an ink ribbon.

 Each pin makes a dot, and combinations of dots form characters and illustrations.

Non-Impact Printer

Type of printer that does not strike or impact paper to produce an image or text, instead, it uses methods such as heat, ink, or toner to create the final output. Examples include inkjet, laser, and thermal printers.

Plotters

A plotter is a printer that interprets commands from a computer to make line drawings on paper with one or more automated pens

• Pen plotter

• electrostatic plotter

• Large-format plotter

Voice output applications

• are useful to blind people

• provide entertainment through music or sound in movies

• are useful for training people in large groups

• useful for making announcements to a large group of people

• are useful for security purposes

Light emitting diodes ( LED )

is a semiconductor device that emits visible light when an electrical current passes through it

can be used for:

• Indicator lights

• Large outdoor screen displays

• illuminate traffic light

Photo printers

• A technology which enables users to print images from the memory card in their digital camera without transferring images to a computer available

Resistive touchscreen

• a touch-sensitive computer display that responds by applying pressure. It's made from two resistive-coated transparent sheets that are separated by a small air gap. When contact is made to the surface of the touchscreen, these two sheets are pressed together.

Capacitive touchscreen

• control displays that utilise the electrical properties of the human body as input. When a finger (or specialised input device, such as stylus) comes in contact with the display it detects when and where on the display the user touches it.

Infared touchscreen

• have a grid-like array of LED lights and photodetectors (sensors) around the edges of the device. While invisible to the naked eye, these LEDs are constantly emitting and projecting light. When you touch the surface, it creates a disturbance in this light.

Smart board

• an interactive whiteboard that uses touch detection for user input

Modems

• a network device that both modulates and demodulates analog carrier signals (called sine waves) for encoding and decoding digital information for processing.

Standard Modem

a device connecting your home to your internet service provider (ISP) through a physical connection.

Cable Modem

• A cable is a device that modulates and demodulates signals for transmission and reception over a cable wiring

DSL Modem

• is a device that modulates outgoing signals and demodulates incoming DSL signals

• Two types of DSL

  • ADSL: downstream throughput is higher than upstream

  • SDSL: downstream and upstream travel at equal capacity

Satellite Modem

• is a device that transforms input signals into radio signals and vice versa

Cables and ports

• A port is a socket on the outside of a system unit which is connected to an expansion board on the inside of the system unit

Power cable

• temporarily connects an appliance to the mains electricity supply via a wall socket or extension

Serial port

• is a physical communication interface through which bits of data are sent and received one bit at a time

Parallel port

• is a physical communication interface through which data is sent and received simultaneously

PS2 port

• is an electronic plug used to plug in keyboards and mice

USB port

• allows many peripherals to be connected using one standard interface

Firewire port

• high speed serial bus which could efficiently interconnect peripherals

Audio/video cables

• RCA: A/V cables used for audio and video transmission

• HDMI: is a digital interface for transferring both audio and video through a single cable