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F452 Computing
2 Variable & Constants
Term | Definition |
---|---|
Variable | An identifier / memory location representing a value needed by the program. The value may change while the program is running. |
Constant | When a constant is declared it must be given a value which cannot then be changed while the program is running. |
Advantages of constants | Descriptive identifier used for a value to make code easier to write/understand. Value only needs to be changed in one place. |
Scope of a variable | That part of a program where the variable is available. e.g. whether it is local or global. If global and local variables use the same identifier, then the local takes precedence. |
Local variable | Declared within a subroutine/block. Only available within that sub/block. Destroyed when the sub/block exits. |
Global variable | Declared at the beginning of a program and is available throughout the program. |
Data Types | Integer (whole number), Real (decimal fractions), Boolean (TRUE/FALSE), Text/string (alphanumeric – a series of characters), Date. Phone number is text NOT an Integer – an integer would lose the leading zero. |
Array | A collection of data items of the same data type stored under one identifier. Each item can be accessed via its index. |
Declaring an array | Identifier (name), size (size -largest index), data type .e.g Dim arrNames(10) As String |
2D Array | A collection of data items of the same data type under one identifier. Uses two index numbers. Can be represented as a grid/table/array of arrays. |
Advantages of arrays | Code is easier to manage/has fewer variables/can use iteration (looping). More efficient than separate variables. |
Serial search on array | Check the array is not empty (report error if it is). Set a counter to 1/0/start from first position. Check if item (at current position) is item searched. If found return the position/value of counter. If not found increment counter/move to next position |