Computing Flashcards
Computer
An electronic, programmable data processing machine
Computer system
A collection of hardware and software that work together to achieve data processing tasks
System
A collection of parts that work together for a defined purpose
System boundary
How a system is separated from the outside world
What is a system boundary often called?
Interface
Importance of computer systems
Improve quality of manufacturing
Cheaper manufacturing
Faster access to information
New ways of doing business
Types of computer systems
General-purpose
Dedicated
Control
Embedded
Expert
Managment information
General-purpose systems
Personal computers that are designed to perform multiple tasks
Dedicated systems
Systems that are specially produced to perform a single function or set of functions
Control systems
Computers systems that control machinery
Embedded systems
Computer systems that are part of a larger system
Expert systems
Systems designed to behave like a human expert
Management information systems
Systems that bring together the information from all parts of an organisation so that managers can make sensible decisions
Data integrity
Data being accurate and consistent throughout its life
De facto standards
Standards that develop over time because of common usage
De jure standards
De facto standards that have become so unviersally accepted that they have to be adhered to or communication is impossible
Proprietary standards
Owned by an organisation. Ensure compatibility between the company’s products
Industry standards
Set by recognised non-commercial organisations
Open standards
Publicly available
Produced collaboratively
Not dominated by any one interest group
Examples of open standards
HTTP
WAP
HTML
XML
Ethical act
An act that is morally “right”.
A legal act
An act that does not break any laws.
Data protection
Laws that intend to protect the privacy of data of individuals on computer systems
Hardware
The physical components of a computer system
Hardware components
Input
Output
Storage
Processing
The central processing unit
Carries out the processing in a computer
The arithmetic and logic unit (ALU)
Carries out all of the arithmetic and logical operations
The control unit
Uses electrical signals to control the flow of data within the CPU
The fetch-execute cycle
Fetch
Decode
Execute
Fetch
The boot sequence
A sequence of processes that contains all the information and instructions to start the computer
Boot loader
A program that starts the boot sequence when the computer is switched on
CPU clock speed
The speed of the fetch-execute cycle
Cache memory
Very expensive
Contains recently used data
Types of memory
Virtual memory
Flash memory
Virtual memory
Part of the hard drive
Used as an extension to RAM
Flash memory
A type of ROM that can be rewritten
Used as a portable medium for storing data
Example of input devices
Mouse – controls a pointer on screen that can be opened, dragged or controlled by clicking buttons on the mouse
Output device example
Monitor - the most common way of displaying text, images and video
Secondary storage
Needed to store data and programs when the power is switched off
Types of secondary storage
Magnetic hard disk
Optical disk
Flash memory
Magnetic hard disk properties
Reliable
High capacity
Low cost
Optical disk properties
Good capacity
Low cost
Lightweight
Portable
Flash memory properties
Good capacity
Used in hand held device
More expensive
Software
The programs we run and data we use on our computers
Multi-purpose computers
Computers that store their software on a secondary storage medium
Graphical User Interface (GUI)
Uses icons to represent resources, files, programs and actions
Types of memory management
Virtual memory
Peripheral management
Fragmentation and defragmentation
Device drivers
Multitasking
Directory
A logical grouping of files, also called folders
File extensions
These are parts of the file name that indicate what type of file it is
Attributes
Files can be given different attributes, which provide extra information about the file
Viruses
Viruses are programs that replicate themselves. They attach themselves to legitimate programs
Authentication
Operating systems usually allow the authentication of users. This normally involves users having a user ID and a password
Privileges
The rights assigned to users and groups
Encryption
Files are transformed in such a way that an unauthorised person cannot understand them
Types of programming software
Editors
Linkers
Interpreters
Editors
They allow text to be created, saved, read and changed
Applications
Are the programs that people use to read-world jobs
Utilities
Software tools that help make maintaining the system easier
Custom written software
Software specially commissioned for a particular customer
Off the shelf software
Ready immediately
Extensively tested
There will be lots of forums online where users can help each other
Open source software
Software that has been placed in the public domain by the programmers
Bit
A binary digit
Units
8 bits = byte, 4 bits = nibble
Converting from denary to binary
Repeated division by 2, recording the remainder each time.
Hexadecimal numbers
Numbers that are easily converted from binary and easy to remember or recognize
Database
A persistent organised store of data on a computer system
Persistent (database)
It is saved on secondary storage for the future
Organised (database)
A structure that can be easily processed
The importance of databases
Accurate
Up to date
Available to those who need to use them
Protected from those who should not have access
Data security
Refers to keeping data safe
Data integrity
Data reflects reality
Validation
The process of checking data when it is input
Validation methods
Length check
Type check
Range check
Presence check
Verification
Checking that the data entered is correct
CRUD
Standard operations on databases are sometimes listed under the term CRUD:
Create Read Update Delete
Data matching
Compares different databases to look fo particular relationships
Data mining
A process that looks in many different unrelated databases
Flat file database
This is just rows and columns such as would be suitable for an address book
Relational database
It is the most useful model and consequently most common type of database
DBMS
Database Management System
Transactions
When a change takes place in a database
Multi-user databases
Most commercial databases are multi-user. This can be a conflict. To avoid this, most DBMSs use record locking
Commons tools provided by a DBMS
Tables
Linking tables
Data types
Forms
Reports
LAN
Confined to one site
Connected using equipment owned by the organisation
Maintained by the organisation
WAN
It is a wide area of network. It covers a large geographical area which may be a city or even the world
Functions of WAN
They often connect LANs together
They make use of publicly available telecoms facilities
They allows a business to function from any location
Network hardware
Special hardware is needed to connect computers to:
Network interface controller (NIC)
Cables
Hubs
Switches
Types of network
Client-server network
Peer-to-peer network
Client-server network
One or more servers provide services to many clients machines where the users work
Peer-to-peer network
In a peer-to-peer network, all computers are equal. Each computer serves the needs of the user as well as carrying out networking functions
Network topologies
The layout of the network components: the cabling and the position of the nodes
Protocols
A set of rules that covers data communication
Flowcharts
It is a diagrammatic representation of the data flow and structure for the solution. Flowcharts use a standard set of shapes to define different actions
Pseudocode
Structured form of English used to define the steps needed to solve a problem
Programming languages
Machine language
Assembly language
High-level language
Integrated development environment (IDE)
Translators usually include an IDE. Features of IDE: - source code editor - error diagnostics - run-time environment - translator - automation tools
Comparison operators
Used to compare two values
Array
A set of variables with the same name and an index number to identify the different variables
Syntax errors
Errors in the use of the language rules and these are often identified by the IDE
Logic errors
Generated by variables not taking the values expected or decisions that not allow the program to complete
Features of a DBMS
Applications won’t damage existing data structures
New applications can be written without restructuring the data
Data can be more easily shared between applications
RAM
Volatile
Contains OS
Stores programs and data being used by the computer
ROM
Non-volatile
Contains boot program
Porgrammed during computer manufacture
Advantages of LAN
Users can communicate with each other
Computer use can be easily monitored
Expensive peripherals can be shared
Operating system
The core software that allows a computer to run as an useful device. Manages the hardware, the user interface and all other software running on the computer
Converting hexadecimal to binary
Split binary number into two nibbles
Convert each to get hex equivalent
Converting binary to hexadecimal
Convert binary into denary, then denary into hex
Converting hexadecimal to denary
Multiply first symbol by 16
Multiply second symbol by 1
Add both symbols
Converting denary to hexadecimal
Divide by 16 and record remainders until result = 0
Compression
Reducing the size of a file
Types of compression
Lossy
Lossless
Lossy compression
Removes some of the data from the file
The data removed cannot be recovered
Lossless compression
Does not store repeated detail
Allows the original file to be reconstructed exactly
Database Management System
An application designed to control all aspects of a database
DBMS functions
Creating an empty database
Deleting an entire database
Creating and deleting tables
Inserting new records into tables
Updating and deleting records
