Variables:

Properties of variables

Variables in a program store information needed by the program to perform its task

Each variable in modern programming languages has the following properties:

a name: symbolic name used to identify (refer to) the variable
an address: the location in memory where variable is stored - the computer uses the address to find the variable in memory
a type: tells the compiler the size of the variable and how to use the value in the variable - see discussion about data type ( click here )
a scope: the range where the variable is accessible/visible
More on scoping much later...
a lifetime: the duration when the variable exists
(variables can be "created" and "destroyed" while the program is running)

More on lifetime much later...
See the following note on "creating" and "destroying" variables: click here

Variable names (identifiers) in C/C++:
- Variable name consists of:
  - letters
  - digits
  - _ (underscore)
- Variable name must begin with a letter or _ (underscore)

Defining variables in C/C++:

The language syntax to define variables in C++ is identical to that in Java

Defining uninitialized variables:

DataType variableName1, variableName2, ... ;
Examples: int a, b, c; // 3 uninitialzied integer variables double x, y; // 2 uninitialzied double precision floats (NOTE: semi-colon is used to terminate a variable definition)

Uninitialized variables do not have a usable value when the variable is created (i.e., you need to initialize it before you can use its value)

Defining initialized variables:

DataType varName1=Value1, varName2=Value2, ... ;
Examples: int a=5, b=9, c=7; // 3 initialzied integer variables double x=7.0, y; // 1 initialzied and 1 uninitialzied // double precision floats