Chapter 1: Communicating with Your Computer

chapter 1

communicating with your computer

English

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We talk to computers with

programming languages.

c++

JavaScript

Chakra V8 SpiderMonkey

http://repl.it/languages/JavaScript

input output

input outputJavaScript Code text, behavior

what is 2 + 2?

4!

2 + 2;

2 + 2;expression

2 + 2;expression

semicolon ends the expression

2 + 2;expression

semicolon ends the expression

arithmetic operator

2 + 2;expression

semicolon ends the expression

arithmetic operator

value value

2 + 2;evaluates to

the value 4

var sum = 2 + 2;

var sum = 2 + 2;expression

assignment operator

identifier

keyword to declare new variable

sum;evaluates to

the value 4

var sum = 2 + 2;

sum = 4 + 10; // sum now equals 14

var sum = 2 + 2;

sum = 4 + 10; // sum now equals 14comment, ignored by the JavaScript engine

var sum = 2 + 2;

sum = 4 + 10; // sum now equals 14

sum + 10; // evaluates to 24

var sum = 2 + 2;

sum = 4 + 10; // sum now equals 14

sum = sum + 10; // sum equals 24

10 - 6; // evaluates to 4

10 * 4; // evaluates to 40

10 / 2; // evaluates to 5

10 - 6; // evaluates to 4

10 * 4; // evaluates to 40

10 / 2; // evaluates to 5

subtraction operator

multiplication operator

division operator

Review

What are the values in this expression?

1 + 45 + 10 + 20;

What does this expression “evaluate” to?

99 + 1 + 10;

What does this expression “evaluate” to?

// 34 + 5 + 1;

What value is the variable bottles set to?

var cans = 2 + 10;

var bottles = 2 + cans - 10 - cans;

Homework #1

Write a JavaScript

expression which adds

5 to 10.

This expression

should evaluate to 15.

Use www.repl.it to

write your code.

Homework #2

Define three variables. One

should hold your age, one

should hold your favorite

number, and one should hold

the number of siblings you

have.

Next, define a new variable

which stores the result of

adding the previous three

variables together.

Homework #3

Define a variable to hold the number

of hours in a day.

Multiply this value by 7 to get the

number of hours in a week. Assign

this to a new variable.

Next, multiply this by the number of

weeks in a year (52) and assign the

result of this in a new variable.

Finally, divide this number by the

number of days in a year (365). What is

the result?

Intro to Programmingwith Seth McLaughlin