IGCSE Computer Science Paper 2 Definitions Worksheet: 8.1c Procedures and Functions (Modules 419–428)
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Key terms
Write what each term means, in your own words.
1
CALL SumSquare(2, 3)
2
FUNCTION
3
DECLARE
4
global variable
5
local vs global
6
local variable
7
main program
8
trace table
9
SumSquare(10, 20)
10
Debugging
Answer Key
IGCSE Computer Science Paper 2 · Modules 419–428 · Student wording will vary for definitions
1CALL SumSquare(2, 3) — A common error when SumSquare is a function. CALL is only for procedures. A function returns a value, so use it in an expression, in OUTPUT, or store it in a variable.
2FUNCTION — Use a FUNCTION when a task produces one value the program needs, such as an area; use a PROCEDURE when it only does something, such as OUTPUT a menu.
3DECLARE — Creates a local variable inside a procedure or function, e.g. DECLARE Length : INTEGER. It exists only while the subroutine runs and cannot be used in the main program.
4global variable — A variable declared outside every subroutine, so the main program and any procedure or function can use and change it. It exists for the whole program.
5local vs global — A local variable is declared inside a subroutine and only exists and works there while it runs. A global variable is declared outside and can be used anywhere in the program all the time.
6local variable — A variable declared inside a subroutine. It keeps the subroutine self-contained, so changing it cannot accidentally alter other parts of the program, and the subroutine is easier to test alone.
7main program — The section after all procedure and function definitions. It calls them in order, using CALL for procedures and function calls inside expressions or OUTPUT.
8trace table — A table used to trace a call: record the value given to each parameter, follow the procedure's statements, then return to the next line of the main program.
9SumSquare(10, 20) — Tracing a call: follow the function's statements to RETURN, then replace the call with the returned value (here 500) and finish evaluating the expression.
10Debugging — Finding and fixing errors by checking a subroutine's header, parameter types, RETURN, CALL, end keyword and variable scope against the syntax rules.