Programming with Scratch

Lesson 1: Intro to Programming

Computer Programming?

What is programming? The process of writing, testing, and maintaining

the source code of computer programs. Telling the computer what to do

Why learn to program? Develops logic and problem-solving skills Improves attention to detail It’s fun!

But I’m Not a Geek!

Until recently, programming required knowledge of computer language syntax

Anyone Can Program!

New tools, like Scratch, allow ANYONE to create computer programs without learning complicated syntax.

Programming with Scratch

Open Scratch from either the desktop icon or Start Menu

Homework

Download and install Scratch on your home computer

Finish working through the Scratch Getting Started Guide

Feel free to experiment and explore!

Programming with Scratch

Lesson 2: Scratch Syntax Part 1

Statements

In programming, a statement is simply a directive that tells the computer to do something. Think of it as a command or an instruction.

In Scratch, any block whose label reads like a command is a statement.

Boolean Expressions

Sometimes, you only want a statement to be executed under certain conditions. Such conditions are defined in terms of Boolean expressions.

In programming, a Boolean expression is an expression that is either true or false. In Scratch, any block shaped like an elongated diamond is a Boolean expression.

Boolean Expressions

One such block is:

After all, it is either true that the mouse button is down or it is false.

Another such block is:

After all, it is either true that some number is less than another number or it is false.

With Boolean expressions can we construct conditions.

Conditions

In programming, a condition is something that must be true in order for something to happen.

A condition is thus said to "evaluate to true" or "evaluate to false."

In Scratch, any block whose label says "if," "when," or "until" is a sort of conditional construct.

Conditions

If Construct: Instruct a sprite to say hello only if, say, the user has depressed the mouse button:

If-Else Construct: Instruct a sprite to say hello or goodbye, depending on whether the user has depressed the mouse button:

Conditions

When Construct: Instruct a sprite to do something when an event occurs:

When Construct: Instruct a sprite to wait to do something until a condition is true:

Loops

In programming, a loop can induce multiple executions of statements.

In Scratch, any block whose label begins with "forever" or "repeat" is a looping construct.

Follow Me

Follow Me applet

Homework

Complete the Cat Walk Project You may wish to use the Scratch Reference

Guide as a resource Completed projects need to submitted by the

due date.

Programming with Scratch

Lesson 3: Scratch Syntax Part 2

Variables

In programming, a variable is a placeholder for some value, much like x and y are popular variables in algebra.

In Scratch, variables are represented with blocks shaped like elongated circles, uniquely labeled by you.

Threads

In programming, a thread is like a mini-program within a program that can execute at the same time as other threads.

In Scratch, any block whose label begins with "when" essentially demarks the start of a thread.

Events

An event is a signal from one thread to another.

Blocks whose labels begin with "broadcast" signal events whereas blocks whose labels begin with "when" handle events.

Copter Game Flight Code

Copter Game—One Level

Adding a Level

Levels can be added using threads and events.

Homework

Complete the Your First Game Project You may wish to use the Copter Game and

Levels program as resources. Completed projects need to submitted by the

due date.