VISUAL PROGRAMMING BY SCRATCH

Transcription

1 Faculty of Information Technology VISUAL PROGRAMMING BY SCRATCH Dr. Nguyen Chi Trung Faculty of Information Technology Hanoi National University of Education

2 Chapter 1. Getting Started

3 What is the Scratch?

4 What is the Scratch? Most programming languages are text based, which means you have to give the computer commands in what looks like a cryptic form of English. For example, to display Hello! on the screen, you might write: print('hello!') (in the Python language) std::cout << "Hello!" << std::endl; (in the C++ language) System.out.print("Hello!"); (in the Java language) 4

5 What is the Scratch? Scratch is a visual programming language, was developed in the Massachusetts Institute of Technology (MIT) Media Lab to make programming easier and more fun to learn. In Scratch, you won t type any complicated commands. Instead, you ll connect graphical blocks together to create programs. Look at the simple program as below: 5

6 What is the Scratch? The cat is called a sprite. Sprites understand and obey sets of instructions that you give them. The purple block on the left tells the cat to display Hello! in a speech bubble. You ll use blocks to make sprites move, turn, say things, play music, do math, and so on. The stacks of blocks that you create are called scripts. For example, the figure bellow shows a script that changes a sprite s color four times. 6

7 SCRATCH REFERENCES Learning programming by Scratch Game Programming Solve Exercises Learning Computer Science Concepts

8 REFERENCES Website of Scratch: 1. Majed Marji (2014), Learn to Program with Scratch, No Starch Press, San Francisco ISBN-10: Jerry Lee Ford (2009), Scratch Programming for Teen, Course Technology USA, ISBN-13: Sergio et al (2014), Scratch 2.0 Game Development, PACKT Publishing 4. Le Lead Project (2014), Super Scratch Programming Adventure, Copyright 2012 by the LEAD Project, Publisher:William Pollock, ISBN-10: Al sweigart (2016), Scratch Programming Playground, Publisher:William Pollock, ISBN-13:

9 REFERENCES 6. Orni et al. (2010),Learning Computer Science Concepts in Scratch, ICER, Aarhus, Denmark, Copyright 2010 ACM /10/08 7. The Magpi (n.d.), Learn to code with scratch, published by Raspberry Pi (Trading) Ltd., Mount Pleasant House, Cambridge 8. Sean McManus (n.d.), Scratch Programming in Easy Steps, Foreword by Mitchel Resnick, ISBN-13: (only 35 pages for review) 9. Jeremy Scott (n.d.), Starting From Scratch An Introduction to Computing Science, The Royal Society of Edinburgh, Scotland's National Academy, Scottish Charity No. SC (62 pages for review) 9

10 Introduction to Scratch Programming Environment Learning programming by Scratch Game Programming Solve Exercises Learning Computer Science Concepts

11 Scratch Programming Environment To start Scratch, go to and download 11

12 The Stage The Stage is where your sprites move, draw, and interact. The Stage is 480 steps wide and 360 steps tall. The center of the Stage has an (x, y) - coordinates of (0, 0). 12

13 Sprite List The Sprite List displays names and thumbnails for all the sprites in your project. New projects begin with a white Stage and a single cat-costumed sprite, as illustrated in the figure bellow. 13

14 Sprite Info You can view the sprite info area by clicking the small icon at the top-left edge of a sprite s thumbnail. 14

15 Manipulate with sprite You can delete, duplicate, hide, remove a sprite from your project or can export a sprite and save to file. You can add new backdrop images with any of the four buttons below the Stage s thumbnail. Click on the Stage icon in the Sprite List to view and edit its associated scripts, backdrops, and sounds. 15

16 Blocks Tab Blocks in Scratch are divided into 10 categories (palettes): Motion, Looks, Sound, Pen, Data, Events, Control, Sensing, Operators, and More Blocks. Blocks are color coded to help you find related blocks easily. Scratch has more than 100 blocks, though some blocks only appear under certain conditions. 16

17 Direction of sprits Some blocks require one or more inputs (also called arguments) that tell the block what to do.. 17

18 Scripts Area To make a sprite do interesting things, you need to program it by dragging blocks from the Blocks tab to the Scripts Area and snapping them together. 18

19 Scripts Area : try it out Start a new Scratch project and create the script below for the Cat sprite. (The forever block is in the Control palette, and the other blocks are in the Motion palette.) 19

20 Costumes Tab The Costumes tab contains everything you need to organize your sprite s costumes; you could think of it like a clothes closet. The closet can have many costumes, but a sprite can wear only one at a time. 20

21 PING-PONG GAME The First Scratch Game

22 Ping - pong game (Version 1.0) Create a single-player game in which players will move a paddle to keep a bouncing tennis ball from hitting the floor, based on the classic arcade game Pong. The user interface for our game is illustrated in the Figure. 22

23 Step 1: Prepare the Backdrop To detect when the ball misses the paddle, we ll mark the bottom of the Stage with a certain color and use the touching color? block (from the Sensing palette) to tell us when the ball touches that color. 23

24 Step 2: Add the Paddle and Ball Click the Paint new sprite button above the Sprite List to add the Paddle sprite to your project. Since the paddle is just a thin, short rectangle, repeat what you did in Step 1 to draw a paddle like the one in the Figure. Color the paddle any way you want and set the center approximately in the middle of the rectangle. Rename the sprite as Paddle. Click Choose sprite from library above the Sprite List to import one. In the dialog that appears, click the Things category and select the Tennis Ball image to add that sprite to your project. Rename the sprite as Ball. 24

25 Step 3: Start the Game and Get Your Sprites Moving Create the script shown in the Figure for the Paddle sprite. Create the script shown in the Figure for the Ball sprite 25

26 Step 3: Start the Game and Get Your Sprites Moving Now, it s time to add the fun part the blocks that make the ball bounce off the paddle. We can modify the forever block we just created so the ball travels upward when it hits the paddle, as shown in the Figure as bellow. 26

27 Step 4: Spice It Up with Sound Double-click the ball on the Stage to select it and then select the Sounds tab. Click the Choose sound from library button to add a sound to the Ball sprite. In the dialog that appears, select the Effects category, choose the pop sound, and click OK to add it to the Sounds tab. After that, go back to the Scripts tab and insert a play sound block (from the Sound palette), as shown in Figure 27

28 MAIN CODE Scripts for Paddle and Ball as below: 28

29 Scratch Blocks: An Overview Scratch has four kinds of blocks: command blocks, function blocks, trigger blocks, and control blocks 29

30 Arithmetic Operators and Functions

31 Arithmetic Operators You could make your own calculator in Scratch with the blocks from the Operators palette. Scratch also supports the operators as bellow: mod (modulus), round. 31

32 Random Numbers The outputs of pick random 0 to 1 and pick random 0 to 1.0 are different. The first case will give you either a 1 or a 0, but the second gives a decimal value between 0 and 1. If any input to the pick random block contains a decimal point, the output will also be a decimal value. 32

33 Mathematical Functions Scratch also supports a large number of mathematical functions. The sqrt of block groups together 14 math functions that can be selected from the drop-down menu, including square root, trigonometric, logarithmic, and exponential functions. 33

34 .. End of Chapter 1