8.1 Programming concepts Lesson Slides

8.1 Programming concepts
Variables and Constants

By Adrian Ortiga

A programs needs to store data

For example:

• The Grades of the students

• The coins you have in Super Mario

• Your username of Wechat account

Variables and Constant are use to store this data

​666

​X

Computer Memory, eg. RAM

Data
values

​Memory
location
(address)

Each variable and constant is on a different memory location

we have number 10

​In memory
location 0

Each Var and Const have an identifier (a name to find the value)

​Here the identifiers are the memory location

Each Var and Const have an identifier (a name to find the value)

But we change it, to more meaningful names

Multiple Choice

What is the difference between a constant and a variable?

• A constant can change, while a variable does not change.
• Both constants and variables can change at any time.
• A constant is a type of variable that can change its value.
• A constant does not change, while a variable can change.

Create, declare, define a variable

Create, declare, define a variable

​Page 200

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

Which one of these is a valid variable name?

• user-name

• 123name

• user_name

• name@user

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

Which variable name is NOT allowed?

• firstPlace

• _winner

• 2ndWinner

• winner2

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

Which variable name is correct?

• user name

• username

• user-name

• user@name

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

Which is the best variable name for storing a person's age?

• age

• number1

• a

• temp

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

Which is an example of camelCase?

• total_price

• TotalPrice

• totalPrice

• totalprice

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

Which variable name is written like a constant?

• max_speed

• MaxSpeed

• MAX_SPEED

• maxSpeed

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

Which variable name is NOT a reserved keyword?

• if

• while

• data

• for

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

In most languages, what is true about Name and name?

• They are the same.

• They are different.

• One is correct, one is wrong.

• They are both wrong.

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

When is it okay to use very short variable names like i or j ?

• In any program.

• When naming user accounts.

• Never.

• Inside a small loop.

Common Variable Naming Conventions
(Rules for the names of variables.)

Multiple Choice

Why should you use the same style (like camelCase or snake_case) in your code?

• To make it look cool.

• To avoid errors.

• To make the code easy to read.

• Because the computer requires it.

Constants

Constants are the variables that CANNOT be changed.

Constants

Some programming languages like Python do not support CONSTANTS.

Data types

The data store in Variables and Constants can be of different types.

Data types

​Page 202

Match

Match the following data with its data type

• String

• Integer

• Real, single, double

• Bolean

• Char

"hello"

666

666.00

False

'h'

• "hello"

• 666

• 666.00

• False

• 'h'