Edexcel GCSE Computer Science Glossary Exam Questions And Complete Answers
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Course
GCSE
Institution
GCSE
Edexcel GCSE Computer Science Glossary Exam Questions And Complete Answers
Compiler
Translates the whole program into machine code at once before the program is run.
1. Code executes quickly (as already translated).
2. Slower to find errors (as all code must be translated).
Interpreter
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Edexcel GCSE Computer Science Glossary Exam
Questions And Complete Answers
Compiler
Translates the whole program into machine code at once before the program is run.
1. Code executes quickly (as already translated).
2. Slower to find errors (as all code must be translated).
Interpreter
Translates source code into machine code, line by line when the program is run.
1. Code can run on different platforms/devices (as it's translated on the platform running
the program).
2. Source code needs to be provided (so competitors could steal your source code
ideas).
Assembler
Translates assembly language source code to machine code.
1. Code can run very quickly and use less memory (as programmer chooses the
machine code instructions).
2. Uses easier to understand assembly language instead of machine code binary values
(so programs can be developed more quickly and with fewer errors).
Translator
A program that translates high-level or assembly language source code into runnable
machine code.
Source code
The high-level or assembly language program instructions the programmers type into
the development environment text editor..
Machine code
The low-level set of instructions built into a CPU, e.g. add, compare, branch or move.
Each instruction is represented by a unique binary code, e.g. 0100101.
Assembly language
A low-level programming language that uses short easier to understand mnemonics,
like ADD, SUB or MOV, to represent machine code instructions. Each mnemonic
translates directly to a machine code instruction.
Mnemonics
Short combinations of letters used in assembly language to help programmer
understand what machine code instruction do, e.g. MOV for move or CMP for compare.
Low level languages
Are programming languages that use binary values (machine code) or short easier to
understand mnemonics (assembly language) in programs.
,Low-level programs can:
1. run more quickly,
2. use less memory,
3. control hardware more easily.
High level languages
Are programming languages which use more English-like statements that are easier for
humans to understand.
Integer data type (int)
Any whole number, e.g. 10.
Real data type (float)
Any number with a decimal point or fraction, e.g. 3.14
Boolean data type (bool)
Any true or false value, e.g. day == "Tuesday" will be True if the day contains Tuesday
or False if it does not. You can also set a variable directly to True or False.
Character data type (str)
Any letter, number or symbol, e.g. "H".
String data type (str)
A sequence of characters, e.g. "Hello".
Variable
A named reference to a memory location containing a value that can be used
throughout a program and be changed. Names should be meaningful, i.e. describe the
values they contain.
Constant
A named reference to a memory location containing a value that can be used
throughout a program but cannot be changed.
Constants make a program:
1. easier to understand (as descriptive names are used instead of just values, e.g. PI
instead of 3.14),
2. easier to update (as the constant only need to be edited in one place, where it is
defined).
Arithmetic Operators
Perform mathematical calculations such as:
addition, e.g. 3 + 2
subtraction, e.g. 3 - 2
multiplication, e.g. 3 * 2
float division, e.g.
integer division, e.g. 3 // 2 (returns an integer)
exponentiation, e.g. 3 ** 2 (raise 1st number to power of 2nd)
modulus, e.g. 3 % 2 (remainder after dividing 1st number by 2nd)
Relational Operators
Used to compare two values and return true or false depending on the result. Operators
can check if:
, left and right values are equal, e.g. value == 3
left value is less than right, e.g. value < 3
left value is greater than right, e.g. value > 3
left value is less than or equal to right, e.g. value <= 3
left value is greater than or equal to right, e.g. value >= 3
Usually used in selection or condition controlled loop statements, e.g. if value == 3, or
while value == 3.
Logical Operators
Used to combine two or more conditions, made using relational operators, to create a
more complex condition, e.g. day == "Sat" or day == "Sun" will be true if day equals Sat
or Sun. The operators are:
and (true if all the joined conditions are true)
or (true if any of the joined conditions are true)
not (true if the condition that follows is not true)
Input
Data that is entered into a computer system, assigned to a variable and processed in a
program. Use the input/output symbol in a flowchart. Use the input command in Python.
Output
Data that is outputted by a program in a computer system. Use the input/output symbol
in a flowchart. Use the print command in Python.
Presence check - input validation
A type of validation check that checks to see that the user has entered a value when
asked to do so by the program.
Length check - input validation
A type of validation check that checks to see that the user has entered the correct
number of characters when asked to do so by the program.
Range check - input validation
A type of validation check that checks to see that the user has entered a value within
the correct range of values when asked to do so by the program.
Lookup check - input validation
A type of validation check that checks to see that the user has entered a value from an
acceptable list of values when asked to do so by the program.
von Neuman stored program concept
A modern computer architecture in which program instructions are stored in main
memory and fetched decoded & executed one at a time by the CPU.
Bus
The copper tracks (wires) on which the addresses, data and control signals move from
component to component.
Address bus
The bus that transmits the memory location of an instruction or piece of data from the
CPU to main memory.
Data bus
The bus that transmits data between the CPU and memory.
Control bus
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