Computer Science

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Design and Programming
A system will be created using a
programming or a suite of programming
languages and applications
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Testing
Ensures that the created system will be useable and that it does not crash.
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Alpha Testing
Still at the developement stage, tested in house. Changes can still be made to the system. In most larger companies that is cone by seperate software testing engineerings
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Beta Testing
External testers. At this stage the software is very close to the finished product and is tested in ways software engineers may not consider. E.g. People intrested in the product
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User Acceptance Testing
Tested in the "real world" by the end users
(people who bought it or staff who will use the system). For example, apps and games have updates. This may be for new features but frequently used to fix buts or fix any weak points in the software.
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Pliot or Distributed Changeover
Used when a business has many sites like a bank. One site is used as a pilot site, that is changed to the new system for a trial period. Problems arise will be fixed not affecting the entire system. Takes a long time
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Direct Changeover
The old system is all moved to the new system at once. Downtime to convert. Risky. Cheap
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Parallel Changeover
Both the old and new system is ran at the same time, this happens until the company is confident to convert just to the new system. Expensive. More staff.
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Phased Changeover
Parts of the new system is activated at a time. Allows users to get use to it. Problems will be indentified and solved before more the system is changed over to the new system. Timely.
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Low Level Language
Little to no abstraction from computer instructions, set architechture, commands or functions. Generally refers to machine code or assembly language.
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High Level Language
Enables programmers that are more or less independant of a particular type of computer. Closer to human language.
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Program
Collection of intructions, performs a specific task
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Syntax
Structure of statements
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Algorithm
A process of rules that is followed in calculations or other problem-solving operations
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Procedural programming
Programming language that follows, in order a set of commands
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Disaster planning
Planning for possible data loss, if data is lost organisations lose money and time
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Backup
A means of keeping copies of
software and data so that these
can be recovered
should there be a loss
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Periodic backup
Backups are performed at a set time
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Six backups Strategy Factors
Content and type, Timing, Frequency, Backup and media, Location, Responsibility
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Full Backup
Everything on the system is backed up
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Differential Backup
Backs up only the changed data, only the data that has chaged since the last backup
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Incremental Backup
Backs up only
the changed data, only the
data that has changed since
the last back up
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Recovery
The process of copying backed up files to wherever these files are needed.
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Variable
A data item that can change in a program, depends on the processing that is taking place
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Integer
Whole number
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Real
Decimal points
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String
Any set of characters
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Char
Single characters
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Boolean
True or false
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DIV
When division occurs with this only the whole number is shown
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MOD
When division occurs with this only the remainder is shown
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Constant
Data item that is declared at the
start of a program and can
never change whilst the program runs.
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WIMP
Windows, Icons, Menus and Pointers
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Ambiguity
Refering to words that sound the same but with different meaning, command words may be understood as input words
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Design Evalution
The development company and the customer decide whether a project has been successful
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Design Validation
Before the developer starts creating the system it is important that the design that has been created is both validated and evaluated
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Register
Temporary data store that holds the current instruction to be executed having been fetched from memory
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ALU (Arithmetic Logical Unit)
Arithmetic operation or logical comparisons allows the program to make decisions
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Control Unit
Fetches each intruction, decodes it for the processor and synchronises it before sending control signals to other parts of the computer.
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Fetch, Decode and Execute
Fetch- the next program command from the computer's memory
Decode- Deciphers what the program
is telling the computer to do
Execute-carries out the requested action
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Program Counter
Stores the address of the next intrusctions to be executed
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MAR and MDR
Current running programs are started in memory meaning they must be loaded into registers
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CIR
Instructions is decoded and executed, another instructions is being fetched into the MDR.
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Accumulator
Any intructions that performs a calculation makes use of ACC
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Parallel Processing
Simultaneous use of several
processes to peform a single job. A job may be split, into a number of task each of which may be processed by any available processor.
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Latency
Delay between invoking the operation any getting a response
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Serial Computing
A problem is broken down into a series of instructions. Instructions are executed sequentially,executed on a single processor
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Clock Speed
Measured in Herz and GHz, generally GHz. A CPU's clock speed rate is measured of how many clock cycles a CPU can perform per second
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RAM (Random Acess Memory)
Enable "Multi-tasking", havign several programs. pWithout it data access would be extremly slow if the CPU was to read program instructions and data from the hard disk. Copies the data needed at that time. Stores data as small charge of electricity in tin
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ROM (Read Only Memory)
A special memory chip. Used to store the boot sequence instructions (BIOS), that our computers need to start up our machines. Data in our ROM cannot be easily over written by the users. Non-volatile
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Virtual Memory
If your RAM is full but you need more RAM hard drive space is used as RAM. Inactive programs are located in vitual memory
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RAM cache
Memory chip used to temporaily stores data. Located between the CPU and main memory. Supplies data faster than RAM as it is closer to the CPU
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Disk cache
Section of main memory between the CPU and disc where data recently read from disc or about to be written to the disc (temporaily before being transferred to the RAM).
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Fragmentation
Files are split up and stored on different parts of the disc
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Defragmentation
Files are put together so they are not split.
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RAID (Redundant Array of Inexpensive Disk)
Used to store access multiple hard drives. Used to reduce datta loss and improve performance
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Rogue Value
A Value that would not normally arise as apart of the inputted data
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Other cards in this set

Card 2

Front

Testing

Back

Ensures that the created system will be useable and that it does not crash.

Card 3

Front

Alpha Testing

Back

Preview of the front of card 3

Card 4

Front

Beta Testing

Back

Preview of the front of card 4

Card 5

Front

User Acceptance Testing

Back

Preview of the front of card 5
View more cards

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