To create a variable:
variableType variableName;
For example:
int a;
To create a variable and initialize it:
variableType variableName = initialValue;
For example:
int a = 2;
If you have a variable declared before, you can assign some value to it:
For example:
int a; // declared previously
a = 2;
Or change the value:
int a = 3; // initalized previously
a = 2;
char : signed 1-byte character value
byte : unsigned 8-bit integer
int : signed 16-bit (on ATMEGA based boards) or 32-bit (on Arduino Due) integer
unsigned int : unsigned 16-bit (on ATMEGA based boards) or 32-bit (on Arduino Due) integer
long : signed 32-bit integer
unsigned long : unsigned 3...
