# OCR computing keywords

Computer system
A combination of hardware and software components that allow input processing and output of data.
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Hardware
Physical components that make up a computer system
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software
the programs that run on a computer
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Input devices
hardware devices that take real world data and convert it into digital form that can be stored on a computer. eg keyboard ,mouse.
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Output Devices
hardware devices that use digital data from a computer to produce a form that a person can understand. eg monitors and printers.
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Reliability
How much you can depend on a computer system being available when you need it.
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Availability
The period of time that a system is operational, (usually expressed as a percentage over time).
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Mean time between failure (MTBF)
a measure of availability often quoted by hardware manufactures
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redundancy
spare hardware components are built into a system so in the event of a component failing, the system can swap over to the spare one.
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disaster recovery
where a company has plans to replace a system quickly if there is a catastrophe. Its designed to minimise the time the system is down.
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Bit
Bit -A Single binary digit (1 or 0)
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Byte
A byte is 8 Bits (8 binary digits of 1 or 0)
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Nibble
Nibble is half of a byte (4 bits)
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Kilobyte
1024 bytes / 2(power10) bytes
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Megabyte
1024 kilobytes / 2(power 20) bytes
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Gigabytes
1024 megabytes / 2(power 30) bytes
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Terabyte
1024 gigabytes / 2(power 40) bytes
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Binary
binary is base 2 number system, used by computers. binary uses the digits 1 and 0.
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Denary
Denary is base 10 number system, how we normally count. it uses digits 0 to 9.
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base 16 number system used by humans to represent groups of four bits at a time. uses digits 0 to F .
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Overflow
when the result of a numeric calculation is too large to be stored in the space reserved for that type of data.
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character set
a set of characters(symbols) represented by a computer. ( eg letters, punctuation an some control characters ). each character is represented by a numerical code that is stored as a binary digit.
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ASCII
ASCII is American standard code for Information Interchange. its a 7 bit character set used by PC's.
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EBCDIC (pr. eb-sid-ic)
extended binary coded decimal interchange code. its an 8 bit character set user by older miniframes.
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Unicode
a 16 bit character set that allows many more characters to be coded.
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Instructions set
the group of instructions available for that specific processor to use. the number of instructions available will depend on the number of bits used.
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Op code
the group of bits in an instruction that represent the operation such as EAT , MOVE or TURN
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Compiler
A piece of systems software that converts a program written in a high level programming language into machine code( binary)
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Machine code
a binary representation of a program
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high level programming language
a programming language written in constructs using language we can understand. eg Delphi ,Visual basic, Java etc
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## Other cards in this set

### Card 2

#### Front

Physical components that make up a computer system

Hardware

### Card 3

#### Front

the programs that run on a computer

### Card 4

#### Front

hardware devices that take real world data and convert it into digital form that can be stored on a computer. eg keyboard ,mouse.

### Card 5

#### Front

hardware devices that use digital data from a computer to produce a form that a person can understand. eg monitors and printers.