Any programming language requires to store values temporarily for different purposes like calculations Adding, multiplying etc.Visual Basic gives the need for variables. You can think of variable, a place in memory of computer for an unknown value.
For example when you call someone, then you call him /her by name, like that every variable has name.
Variable name is the word which you use to refer to the values that the variable contains.
VARIABLES:- Naming convention
There are different rules for assigning names to variables ,these are as follows:
A variable name must begin with a letter.
For example:
6date – Invalid variable name
date6 – valid name
Two variables must not contain the same name.
It can not contain a dot or space.
For example:
Num2 – Valid variable name
Num.2 – Not Valid
Num 2 – Not Valid
A variable name must not exceed 255 chracters.
A variable name must not contain any special characters like %, $ , * , & ,! ,@ etc.
For example:
@num, num$r are not valid variable names.
The term declaring a variable means that the memory is allocated .This memory will be referred by a name decided by the programmer.The specific data type decides the amount of memory allocated.
You can declare a variable with a Dim statement by giving a name for the variable according to rules of naming conventions.
Syntax: Dim variablename as Datatype
Example: Dim a as integer
In above example ‘a’ is variable name and integer is the data type.
Rules for declaring variables:
(i) Declaring a variable using the word Public makes it available throughout the program.
(ii) Declaring a variable using the word Static keeps it’s value preserve until a procedure ends.
(iii) Declaring a variable in the declaration section of the form makes it available to all procedures in that module.
For example:
Let us consider the variable ‘var1 ‘An integer variable ‘var1‘ is declared. At the same time memory is allocated for the variable.
The variable is given value 20 during the running state of the program. This value is stored in the given memory location.
This process is shown in figure: