Studied by 12 people
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
The control unit
Arithmetic Logic Unit (ALU)
Memory
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
