Chapter 2 Computers
Central processing unit
Memory devices : Main memory device
What is a computer:
-Machine
-Accepts data which is entered into the machine
-Process - the data is entered without human assistance by means of instructions which are stored.
-Supplies information requested
Networks
Output devices
Input devices
Memory devices : Secondary memory device
Network storage
Software
Components of a computer
Program language
Measuring computer speed
Hardware:
-Physical devices
-Keyboard
-Monitors
-Processing units
Software:
-Programs written in computer language
-Binary code : 0s and 1s
Accuracy:
-Computer's dont make mistakes
Storage and retrieval:
-Storage = saving data in computer memory.
-Retrieval = accessing data from memory
-Data is stored in bits
-A bit = single value of 0 or 1
-8 bits = 1 byte
Speed:
-Number of instructions per second
Arithmetic logic unit ----- control unit
Multi processor:
-More than one central processing unit
-Performs better than a single processor
Send data and information to computer
Capable of representing processed information from computer
Types of devices:
-Keyboard
-Mouse
-Touch screen
-Tablet
Types of devices:
-Computer screens = soft copy
-Printers = hard copy
Semiconductor chips which can be:
-Volatile memory
^RAM - Random access memory (data can be written and read on RAM)
^Cache RAM (stores newly acquired memory
-Non-volatile memory
^ROM - read only memory
^Data can not be written to memory
^Data can read from memory
Used for storing large data and volumes for long periods
3 main types
Non-volatile memory
Magnetic disk
-Random access processing = data is obtained in any order, regardless of its order on the surface
Magnetic tape:
-Stores data sequentially = backup storage (not used much)
Optical disc:
-Stores large amounts of data and durable
-CD-ROM = compact disc read only memory
-WORM = write once, read many
-DVD = digital versatile disk
Cloud storage:
-Online storage and backup
-Various virtual servers operated by third parties
Redundant array of independent disks:
-RAID
-Collection of disk drives that are used for fault tolerance and improved performance
-Used in large network systems = improve network reliability
Storage area network
Network-attached storage
Network-connected computer dedicated to providing file-based data storage services to other network devices
Connect and manage shared storage devices
Makes storage devices available to all servers on a network
Dedicated high speed network consisting of both hardware and software
WAN
MAN
LAN
Connects webstations and devices that are near to each other and owned by one party
Spread over several cities, states and even countries and are usually owned by multiple parties
Is designed for data communication between various organisations in a city, and sometimes between nearby cities
The language selected depends on the problem which needs to be solved as well as the type of computer being used
Source code - programme using object code
Provides step-by-step instructions for performing a specific task
Object code - consists of binary 0's and 1's
Source code is used to write processing instructions or program the computer
Binary - binary digits 0's and 1's (bits) used to store and write data and instructions
Operating system software
Application software
Programs that run a computer system:
Set of programs for controlling and managing computer hardware and software
E.g.
-Word processing - MS word
-Data basis - MS Access
-Spreadsheets - MS Excel
-Project management - MS projects
-Desktop publishing - Adobe
-Financial - Pastel
-Presentation - MS powerpoint
-Graphs - MS Excel
-Computer aided design
Provides on interface between a computer and the user
Increases computer efficiency by helping users share computer resources and performing repetitive tasks for users
E.g.
-Task management
-Resource allocation
-Data management
-Communication
Repetitive tasks for users to perform
In-house development = self developed
Commercial software = purchased