A quantity or function that may assume any given value or set of values (source – Dictionary.com)

What types of values have we assigned to variables in mathematics and science?Integers and Real NumbersTemperature and WeightNames and Places

Being the first or earliest of the kind or in existence

Given just one group of binary digits, what types of things could we come up with?A Binary Value (True/False)Numbers (1, 4, 21)Characters (A, k, &)

Binary Value (boolean) Numbers

Integer (byte, short, int, long) Real Numbers (float, double)

Character (char) Text (String) – not a regular primitive variable!

Each one consists of a different number of bits.

For example, a byte consists of 8 bits and holds a value from –128 to 127.

Calculate28 = 128 + 127 + 1 =

shortOccupies 16 bits or 2 bytes

intOccupies 32 bits or 4 bytes

longOccupies 64 bits or 8 bytes

Can you guess the range of values each one stores?

It’s a tradeoffThe greater number of bytes each one stores,

the greater the range of values it can represent.

But the larger number of bytes used put more demand on memory resources.

floatOccupies 32 bits or 4 bytes, with 6 or 7

significant digits.double

Occupies 64 bits or 8 bytes, with 14 or 15 significant digits.

charContains a standard ASCII character

booleanContains a TRUE/FALSE value

StringContains a line of text

The only ones that you need to be familiar with for the AP Exam are:

1. int2. double3. boolean4. char5. String

variable_type variable_name;Example:

int x;double temperature;char initial;boolean light;String sentence;

Must start with a letter, underscore(_), or dollar sign($)

After 1st letter, you can use numbersCan NOT be a JAVA keywordWhite Space is not permitted (space).No Special CharactersThey are case sensitive so “BOX” is not the

same name as “box”

abstract continue for new switchassert default goto package synchronizedboolean do if private thisbreak double implements protected throwbyte else import public throwscase enum instanceof return transientcatch extends int short trychar final interface static voidclass finally long strictfp volatileconst float native super while

The first letter of the variable is lower case.When using more than one word in the

variable name, the first letter of each word after the first is capitalized.

Be descriptive (to a limit)

If we wanted to have a double that stores the room’s temperature:

The Gooddouble roomTemperature;

The Baddouble ZED;double theTemperatureInOurComputerRoomOnSeptemberTheTenth;

The Ugly (Illegal)double case;double room Temperature;double 9/10/07Temperature;

Variables can be initialized when they are declared:int butterbeerBottles = 99;double bodyTemperature = 98.6;char display = ‘a’;boolean light = false;String insult = “You Strink!”;

A variable can be turned into a constant by adding the word final at the beginning of the declaration.