You can think of Computer Memory as a big table or as rows (and 2 columns) of a spreadsheet.

A Variable in Math

Favorite variable names?

x y z

2x - 9 = 27

y = 2x - 9

• one correct value

• many values
• (in)dependent

A Variable in Programming

a name for a location in memory

speed = 85

think of it as a box with a label, where the box can store numbers and other types of data

Variable

a name for a location in memory that stores data

speed

stop

firstName

assign the value on the right side to the name on the left

speedLimit = speed - 25

does not mean equals but assign

=

Not a valid math equation!!!

speed = speed - 25

often reuse the same box (i.e. name) for the new value

before assignment

after assignment

85

60

Use meaningful variable names

u = 4

p = 2.5

x = 0.1

T = u * p + (u* p * x)

units = 4

price = 2.5

taxRate = 0.1

totalPrice = units * price + (units * price * taxRate)