Help your kids with computer coding _ a unique step-by-step visual guide, from binary code to building games_clone

199C O M P U T E R L A N G U A G E S Languages from the past REAL WORLD Many languages that were famous twenty or thirty years Millennium bug ago have fallen in popularity, despite still being used in some very important systems. These languages are often Many programs in older languages seen as difficult to code by modern standards. like COBOL used two digits to represent a year (such as 99 for BASIC Designed in 1964 at Dartmouth College, in the 1999). The “millennium bug” was US, BASIC was very popular when home predicted to cause problems in computers first became available. 2000 when these dates rolled over into the new millennium as 00. Fortran Designed in 1954 at IBM, a technology firm, Fortran Computers all over is mainly used for calculations on large computers. the world had to be It is still being used in weather forecasting. updated to prevent the millennium bug COBOL Designed in 1959 by a committee of experts, COBOL is still being used in many business and banking programs. Weird languages (‘&%:9]!~}|z2Vxwv-,POqponl$Hjig%eB@@>a=<M:9[p6tsl1TS/ QlOj)L(I&%$””Z~AA@UZ=RvttT`R5P3m0LEDh,T*?(b&`$#87[}{W Among the thousands of languages are a few that have been created for very △ Malbolge specific and strange purposes. The Malbolge language was designed to be impossible to program. The first working code did not emerge until two years after its release, and was written by another program. △ Piet △ Chef △ Ook! Programs created in Piet code look like abstract art. The “Hello World!” A program written in Chef is Designed to be used by program is shown above. meant to resemble a cooking orangutans, Ook! has only three recipe. However, in practice, elements: “Ook”, “Ook!”, and the programs rarely produce “Ook?” These can be combined useful cooking instructions. to create six commands, such as “Ook! Ook” and “Ook? Ook!”

200 P R O G R A M M I N G I N T H E R E A L W O R L D SEE ALSO Coding stars  18–19 Becoming Computing is driven forward every day by millions of a coder programmers all around the world, but every now and then someone special comes along and takes a massive Computer 204–205 leap. Here are a few of the most famous coders. games Ada Lovelace Alan Turing Nationality: British Nationality: British Dates: 1815–52 Dates: 1912–54 FccIfaBnoEocisrmrannouems1bogtsmpg8piubiprgd4npseuaree3efusogtsr,oeetgee(tsrenrae’:drhsrptadApe)iAtm.rndromopSnogaghufbapeocLrelbetoyahrohlsatmtiaCvoieshlcreshhddmeaaolaesacleferdtciflarreoee.strrrshtlsiyse tWGhcgHfreeoArFaaeroraBltcml’ahsumdkrnienaaitoWnrinTldussguoa-shocbrrfsf.oiforecInadeIrocgm:faermoMkesiorsitpdnaukutugsnhtrfoweeionrwmorgsnrhackitiaseicsnitachnee. as numbers. Bill Gates and Paul Allen Grace Hopper Nationality: American Nationality: American Dates: Gates 1955–present, Allen 1953–present Dates: 1906–92 Famous for: Bill Famous for: Grace Hopper created Gates and Paul the first programming language Allen founded compiler (which transforms human Microsoft together readable programs into machine in the 1970s. They code). As well as being a invented some of computer scientist the most popular she was a Rear programs ever, such as Admiral in the Microsoft Windows US Navy! and Office.

201C O D I N G S T A R S Gunpei Yokoi and Shigeru Miyamoto Tim Berners-Lee Nationality: Japanese Nationality: British Dates: 1955–present Dates: Yokoi 1941–97, Miyamoto 1952–present FCrTtaaeEhimnmsReedoNaWBumrse(coafarhrondflrdacee:merWWsinto-ithLfduereielerseeeisWniwcnfeioSovebwrern,kntitiitnfzeiegcdralatnd), Famous for: Yokoi and Miyamoto worked for ekEvnlieizgrayhboteentdeh.bIHIyienQw2ua0es0e4n. Nintendo, the gaming company. Yokoi invented the Game Boy, while Miyamoto made successful games such as Super Mario. Larry Page and Sergei Brin Mark Zuckerberg Nationality: American Nationality: American Dates: Both 1973–present Dates: 1984–present FPwbasTasrmeeohegeacroaevekrouroicracmsohlhnuefneoefdtmfirwnteo:BhgecnIhrnettiiianhinzvG1teeoeb9wo.dd9eoo6ggu,allend Famous for: Zuckerberg the Internet. launched Facebook from his college room in 2004. Facebook has since become a billion-dollar company, and made Zuckerberg one of the wealthiest people alive. Open Source Movement Nationality: All Dates: Late 1970s–present Fpbfoaorepmorefgmorreuraaaestmnifanoynmgrsd: iesTgayrhnvsseatiafeioirlcmaopabuenalnnetndptsdootieWhuacelrileck.wsTeiphoomeefrdlosdmiovawofe,tvmthwheoeaemnrboeete,nnilsslitieunhavceaehcsoesabnlolseecftetcyhwntceilaoroeGrnpesNeopsUdfohi/noaLsu.iinbldulex

202 P R O G R A M M I N G I N T H E R E A L W O R L D SEE ALSO Busy programs  180–181 Inside Computers and programs have become an invisible a computer part of daily life. Every day, people benefit from very complex computer programs that have been written  192–193 Storing to solve incredibly tough problems. data in files Compressing files REAL WORLD Almost every type of file that is sent over the Internet Music files is compressed (squeezed) in some way. When a file is compressed, data that isn’t needed is identified and Without music compression thrown away, leaving only the useful information. programs, you could only fit a few songs on your music player. ◁ Squeezing data By compressing audio files, the Compressing a file is average smartphone can now like squeezing a hold thousands of songs. jack-in-the-box to make it fit into a smaller space. Secret codes ◁ Cryptography When you log in to a website, Cryptography is the buy something, or send a study of codes. Complex message across the Internet, mathematical codes smart programs scramble your scramble and unscramble secret data so that anyone who personal data to keep it intercepts it won’t be able to safe from thieves. understand it. Global banking systems rely on these advanced programs capable of hiding secret information.

203B U S Y P R O G R A M S Artificial Intelligence △ Medicine △ Bomb disposal Intelligent programs do more Systems are able to analyze a Many soldiers’ lives can be than just make computer games huge database of medical saved by using an intelligent fun. Artificial Intelligence (AI) information and combine it robot to safely dispose of a is being used to provide better with details from the patient bomb in an area that has been healthcare, as well as helping to suggest a diagnosis. cleared of people. robots operate in places too dangerous for humans to go, such as war zones and areas destroyed by natural disasters. Supercomputers REAL WORLD Supercomputers—used by high-tech organizations such Weather forecast as NASA—combine the power of thousands of computer processors that share data and communicate quickly. The Weather patterns are very result is a computer that can perform millions of unpredictable. Supercomputers calculations per second. crunch the huge amounts of data needed to accurately predict what 2 Computer 3 Each processor works on will happen. Each processor in the breaks problem one of the smaller problems supercomputer calculates the weather for a small part of the map. into smaller, 4 Each sub-problem is All the results are then combined sub-problems solved separately to produce the whole forecast. 5 Computer puts results back together 1 Complex problem 6 Final result appears is entered into much faster supercomputer △ How it works Problems are broken into smaller problems that are all worked on separately at the same time by different processors. The results are then combined together to give the answer.

204 P R O G R A M M I N G I N T H E R E A L W O R L D SEE ALSO Computer games  200–201 Coding What does it take to make a modern video game? stars All computer games are a different mix of the same ingredients. Great games are usually made by teams Making 206–207 of software developers—not just programmers. apps Who makes computer games? Even simple games on your mobile phone might be made by large teams of people. For a game to be popular and successful, attention to detail needs to be given to every area during its development, which involves many people with lots of different skills. △ Coder ◁ Level designer △ Graphic designer Programmers write the code that will make the The architects of the game’s All of the levels and game work, but they can virtual world, level designers characters need to only do this with input create settings and levels look good. The graphic from the rest of the team. that are fun to play. designers define the structure and appearance △ Scriptwriter of everything in the game. Modern games have interesting plots just like ▷ Tester LINGO great books and films. Scriptwriters develop Playing games all Consoles all the characters and day may seem like a stories for the game. great job, but testers A console is a special type of often play the same computer that is well suited to level over and over running games. Consoles, such as again to check for bugs. the PS4 and Xbox One, often have advanced graphics and sound processors capable of running many things at once, making more realistic games possible. ◁ Sound designer Just like a good movie, a great game needs to have quality music and sound effects to set the mood.

COMPUTER GAMES 205 Game ingredients The most common ingredients in games are often combined into a “game engine”. Engines provide an easy-to-use base so that new games can be developed quickly. ▷ Story and game logic All games must have a good story and some sort of goal to aim for, such as saving the princess. Well-designed game logic keeps players interested. ◁ Game physics △ Graphics In a virtual world, the rules of the As games become more realistic their real world, such as gravity and graphics must become more complex. collisions, must be re-created to Body movements, smoke, and water are make the game more believable. particularly hard to get right. ▷ Controls ▷ Sound Familiar controls that make sense to All of the words spoken in the the player help make a great game. game must be recorded, as well Good control design makes the player as the background music and forget that they are using a controller. the sound effects that change throughout the game. Open the pod bay doors, Hal I’m sorry Dave, I’m REAL WORLD afraid I can’t do that Serious games △ Artificial intelligence Games are being used for more than just fun. Pilots, Human players often play alongside or surgeons, and soldiers are just against computer-controlled players. some of the professionals Artificial intelligence programming allows who use games at work for these characters to respond realistically. training purposes. Some businesses even use strategy games to improve their employees’ planning skills.

206 P R O G R A M M I N G I N T H E R E A L W O R L D SEE ALSO Making apps  190–191 Essential Mobile phones have opened up a world of possibilities programs for coders. With a computer in everyone’s pocket, mobile apps can use new inputs, such as location-finding and  198–199 Computer motion-sensing, to give users a better experience. languages What is an app?  204–205 Computer “App” (short for “application”) is a word that describes programs that run on mobile devices, including games smartphones, tablets, and even wearable technology such as watches. There are many different categories ◁ Social network of apps that do different things. Social apps can allow people to connect with ◁ Games friends, whether they are All sorts of games are available on mobile nearby or far away, to devices, from simple puzzle games to share thoughts, pictures, fast-paced action adventures. music, and videos. △ Weather △ Travel Mobile apps use your location to Travel apps use your location provide accurate weather forecasts, combined with other users’ reviews and also allow you to check the to provide recommendations for weather around the world. restaurants, hotels, and activities. ◁ Sport △ Education People use apps to track their fitness Educational apps are great for when running or cycling, and can also learning. Young children can learn keep up to date on the latest sports to count and spell, and older scores while on the go. people can learn a new language.

207M A K I N G A P P S How to build an app There are many questions to answer before building an app. What will it do? What devices will it run on? How will the user interact with it? Once these questions are answered, building an app is a step-by-step process. Mac 1 Have an idea Any idea for a new app must be well suited to Android mobile devices. It might be a completely new idea, or it could just be an improvement on an already Windows existing idea to make a better version. 2 Which operating system? 3 Learn to make apps Will the app target a certain type of Whichever platform the app will run on, mobile device? Coders can often use tools that a coder needs to learn the language and other let them write their application once and then skills needed to build a good app. Online adapt it for different operating systems. tutorials and local coding clubs can help. 4 Create the program 5 Test it Good apps take time to make. A basic Users will quickly get rid of an app if it contains version might be working in weeks, but for an bugs. Putting in tests as part of the code, and getting app to be really successful, it will need to be friends and family to try out the app can help clean developed for a few months before its release. up any errors before the app is released.

208 P R O G R A M M I N G I N T H E R E A L W O R L D SEE ALSO Programming  198–199 Computer for the Internet languages Websites are built using coding languages that work just like Python. One of the most important of these Using 210–211 is JavaScript, which makes websites interactive. JavaScript How a web page works CSS ◁ CSS Most web pages are built using several The language CSS different languages. An email website, for (Cascading Style instance, is made with CSS, HTML, and Sheets) controls the JavaScript. The JavaScript code makes the colors, fonts, and site respond instantly to mouse clicks layout of the page. without having to reload the page. INBOX CONTACTS CALENDAR Compose ▼ Delete + Move Inbox ▢ Sam Funny cat video Drafts ▢ Lizzie Presents for Ben Sent ▢ Fiona Lunch? Spam ▢ Shaila No thanks Trash ▢ Paula Come to my party? ▢ Dan Re: Barnyard dance ▢ Ben Re: Amazing picture JavaScript ▢ Sarah Hockey match ▢ Vicky Re: New York ▢ Ella Book review ▢ Phil Ben’s presents HTML ◁ HTML ▷ JavaScript HTML (HyperText Markup JavaScript controls how the Language) builds the basic page changes when you use structure of the page, with it. Click on an email, for different sections that instance, and JavaScript contain text or images. makes a message open up.

209P R O G R A M M I N G F O R T H E I N T E R N E T HTML <html> Blocks of text are surrounded by “tags”, a <head> very common feature in HTML code. This When you open a website, your tag gives the window a title Internet browser downloads an HTML file and runs the code to turn <title>The Hello World Window</title> it into a web page. To see how it works, type the code here into an </head> IDLE code window (see pp.92–93) and save it as a file with the ending <body> “.html”. Double click the file and it will launch a browser window <h1>Hello World in HTML</h1> saying “Hello World!” <p>Hello World!</p> The “<p>” and “</p>” tags surround </body> This tag shows where ordinary paragraphs </html> the HTML code ends Trying JavaScript EXPERT TIPS It’s easy to experiment with JavaScript Games in JavaScript because all modern web browsers can understand it. JavaScript code is usually placed JavaScript is so good at within HTML code, so the example below uses creating interactive features two coding languages at once. The JavaScript that it can be used to make section is surrounded by “<script>” tags. games—from simple puzzles to fast-paced racing 1 Write some JavaScript games. These will work in Open a new IDLE code window and type out any modern web browser, so the code below. Check the code very carefully. If there’s no need to install there are any errors, you’ll just see a blank page. the game first. JavaScript is also used to create web <script> The “<script>” tag apps such as webmail or introduces JavaScript code interactive calendars. alert(“Hello World!”); </script> The “alert” command will make an alert box pop up 2 Save your file 3 Pop-up appears Save the file and enter a filename such as “test.html” The browser will open and an interactive alert box so the code is saved as an HTML file and not a Python file. Then double click the file to test it. will pop up with the greeting “Hello World!” Click “OK” to test.html dismiss the box. Don’t forget to give your JavaScript filename an “.html” ending creates interactive JavaScript features such as buttons Hello World! OK

210 PROGRAMMING IN THE REAL WORLD Using JavaScript SEE ALSO JavaScript is great for creating mini programs that run  162–163 Reacting inside HTML, bringing websites to life and allowing users to interact with them. Although it works like Python, to events JavaScript code is more concise and trickier to learn.  122–123 Loops in Python  208–209 Programming for the Internet Getting input This line creates a The text in quotes pop-up box and appears in the box As with Python, you can use JavaScript to ask the user stores the text the for information. JavaScript can do this with a pop-up user types into it box. The following program prompts the user to enter their name and responds with a greeting. 1 Use a prompt <script> This short script stores the user’s name in a var name = prompt(“Please enter your name”); variable. Type the code into the IDLE code window and var greeting = “Hello ” + name + “!”; remember to save it with a “.html” filename. document.write(greeting); JavaScript lines </script> always end with a semicolon The “</script>” tag shows This line displays EXPERT TIPS where the JavaScript ends the greeting Type carefully 2 Question appears Double-click the HTML file to launch When working with JavaScript, be a browser window. Enter your name in the careful to check that you’ve typed box and click “OK” to see the greeting. out the code correctly. If there’s an error, the browser will simply JavaScript A prompt box ignore the whole block of always has “OK” JavaScript and Please enter your name and “Cancel” will create a buttons blank window, Charlie without any error message saying OK Cancel The greeting what went wrong. appears in the If that happens, <> browser check the code window again carefully. Hello Charlie!

211U S I N G J A V A S C R I P T Events 1 Type the code In this example, an event (clicking a button) triggers a An event is any action simple function (a tongue-twister appears). Type the code in that a program can an IDLE code window and save the file with a “.html” ending. detect, such as a mouse click or a keystroke. The <button onclick=“tonguetwist()”>Say this!</button> section of code that <script> Name of the function HTML code links the reacts to an event is function to a button called an “event handler”. function tonguetwist() Event handlers are used a { Curly brackets surround a block of code—they work in a similar way to indents in Python lot in JavaScript and can document.write(“She sells seashells”); trigger many different } functions, making web </script> JavaScript code defines the function pages fun and interactive. Click the The tongue-twister button appears 2 Run the program <> <> Double-click the file to launch the program in a Say this! She sells seashells browser window. Loops in JavaScript 2 Loop output Save the code as a “.html” file and run A loop is a section of code that repeats. Using it. The loop keeps repeating as long as “x” loops is much quicker and easier than typing is less than 6 (“x<6” in the code). To out the same line of code over and over again. increase the number of repeats, use a higher number after the “<” symbol. 1 Loop code Like Python, JavaScript uses “for” to set up a loop. The repeated lines of code are enclosed in curly brackets. This loop creates a simple counter that increases by one each time it repeats. <script> The “<script>” tag introduces <> the JavaScript code Loop count: 0 for (var x=0; x<6; x++) This line creates a counter Loop count: 1 The loop { called “x” with a starting value Loop count: 2 repeats six times of 0, rising by 1 in each repeat Loop count: 3 Loop count: 4 document.write(“Loop count: “+x+”<br>”); Loop count: 5 } This line tells the computer to </script> write the text “Loop count:” followed by counter number

212 PROGRAMMING IN THE REAL WORLD Bad programs SEE ALSO Not all programs are fun games or useful apps. Some  194–195 The programs are designed to steal your data or damage your computer. They will often seem harmless, and Internet you might not realize that you have been a victim.  202–203 Busy programs Malware △ Virus Programs that do things without your knowledge or Just like a virus in the human body, permission are known as “malware”. Unauthorized this malware copies itself over and over access to a computer is a crime, but there are many again. They are usually spread through different types of programs that still try to sneak on emails, USB sticks, or other methods of to your computer. transferring files between computers. ▷ Worm A worm is a type of malware that crawls around a network from computer to computer. Worms can clog up networks, slowing them down—the first worm brought the Internet to a virtual standstill in 1988. △ Trojan REAL WORLD Malware that pretends to be a harmless program is Famous worm known as a “trojan”. The word comes from a ruse used in the Trojan War: the Greeks gave the Trojans a giant On May 5, 2000, Internet users in the Philippines wooden horse, with soldiers hidden inside. By breaching received emails with the subject “ILOVEYOU”. An the Trojan defenses without detection, they won the war. attachment appeared to be a love letter, but was actually a piece of malware that corrupted files. ◁ ILOVEYOU This worm quickly spread to computers around the world. It is estimated to have cost more than $20 billion to fix the damage it caused.

213B A D P R O G R A M S What malware does Viruses, worms, and trojans are all types of malware that are created to get into your machine, but what do they do once they have infected their target? They might delete or corrupt files, steal passwords, or seek to control your machine for some larger purpose as part of an organized “zombie botnet”. ▷ Zombie botnets LINGO Botnets are collections of infected computers that can be used to send Hackers spam emails, or flood a target website with traffic to bring it crashing down. Coders that study and write malware are known as “hackers”. Good software to the rescue Those who write malware to commit crimes are known as Thankfully, people aren’t defenseless in the fight against “black-hat” hackers, and those malware. Anti-malware software has become big who write programs to try to business, with many providers competing to provide protect against malware are the best protection. Two well-known examples are known as “white-hat” hackers. firewalls and antivirus programs. △ Antivirus programs △ Firewalls White-hat hacker Black-hat hacker Antivirus software tries to detect Firewalls aim to prevent malware malware. It identifies bad and dangerous network traffic programs by scanning files and from reaching your computer. comparing their contents with a They scan all incoming data database of suspicious code. from the Internet.

214 PROGRAMMING IN THE REAL WORLD Mini computers SEE ALSO Computers don’t have to be big or expensive. A wide  180–181 Inside range of small and cheap computers are available. Because of their small size and low cost, these computers a computer are being used in lots of new and exciting ways.  202–203 Busy programs Raspberry Pi LED lights show the Pi is working The Pi is a credit-card-sized computer, created to teach the basics of how computers work. For its size it is impressively powerful, Two USB connectors for with the ability to run similar programs to a modern PC. a mouse, a keyboard, or any other add-ons Audio output for headphones or speakers Video output for older TVs Input and output pins for sensing and control (good for robots) Removable memory Network connection to card stores operating access the Internet systems, programs, HDMI video output—to and data connect to modern TVs Power connector Arduino Many input and output Microcontroller—a pins make the Arduino single-chip computer The Arduino is cheaper than very adaptable the Pi, but less powerful. It is often used as a low-cost Reset button and simple way to build custom electronic or robotic machines. Sockets for connecting the USB connector used to Arduino to other load programs on to the electronics Arduino from a PC Power connector

MINI COMPUTERS 215 Using mini computers There are endless useful things a mini computer can do because of its many connection options. Here are just a few suggestions. △ Computer △ Audio output △ Mobile phones △ Gadgets Connect a keyboard, mouse, Connect a set of speakers Connect the computer Connect LED lights and and monitor for a fully and then send music to to the Internet using a other simple electronics to working desktop computer. them over the network. mobile phone. make robots or gadgets. △ Television △ Camera △ USB △ SD card Connect a TV and use it as a Connect a basic camera Connect a USB hard drive Change the programs on media center to show all of to your mini computer to and share your files over your mini computer just your movies and pictures. create your own webcam. your network. by swapping SD cards. REAL WORLD Robotic spider controlled by the Arduino Home-built robots With their small size, cost, and weight, mini computers are being used more and more to build different types of robot. For example: Weather balloons that record weather conditions in the atmosphere. Mini vehicles that can sense obstacles using sonar like a bat. Robotic arms that pick up and move different objects.

216 PROGRAMMING IN THE REAL WORLD Become a master SEE ALSO programmer  176–177 What next? The secret to becoming a master programmer is to  214–215 Mini have fun. As long as you’re enjoying yourself, there’s no limit to how skilled you can become at coding, computers whether as a hobby or a lifelong career. △ Code a lot Ways to become a better programmer People say practice makes perfect—and it’s true. The Like skiing, learning the piano, or playing tennis, coding is a more code you write, the skill that you’ll get better and better at over time. It can take better you’ll get. Keep going years to become a true expert, but if you’re having fun on and you’ll soon be an expert. the way, it will feel like an effortless journey. Here are a few tips to help you become a master programmer. ◁ Be nosy △ Steal ideas Read websites and books about If you come across a great program, think how you programming and try out other might code it yourself. Look for clever ideas to use people’s code. You’ll pick up in your own code. All the best programmers copy expert tips and tricks that might each other’s ideas and try to improve them. have taken you years to figure out on your own. ▷ Show a friend ▷ Train your brain Teach someone else to Your brain is like a muscle— code and you’ll learn a lot if you exercise it, it will get yourself. Explaining how stronger. Do things that coding works is a great help you think like a way of making sure you programmer. Solve logic understand it thoroughly. puzzles and brainteasers, take up Sudoku, and work on your math.

BECOME A MASTER PROGRAMMER 217 ▷ Test your code Scala Pascal SQL Ruby on rails C++ Test your code by entering crazy values to see what happens. See how well it stands up to errors. Try rewriting it to improve it or try rewriting someone else’s— you’ll learn all their secret tricks. ◁ Build a robot army △ Learn new languages You can connect your computer Become multilingual. Every new programming to all sorts of programmable language you learn will teach you more about the devices, from flashing LED ones you already know (or thought you knew). You lights to robots. It’s fun and can download free versions of most languages. you’ll learn lots as you figure out how to conquer the world. ▷ Win a prize When your skills develop, ▷ Pull a computer to bits why not enter an online Take an old computer apart coding contest? There are lots to see how it works (ask to choose from at all different permission first!). There levels. The toughest are aren’t many components, worldwide competitions like so it won’t take long to Google’s Code Jam, but there figure out what all the bits are easier challenges too. are. Best of all, build your own computer and then run your code on it. REMEMBER Have fun! Coding is a lot like trying to solve puzzles. It’s challenging and you’ll often get stuck. Sometimes it’s frustrating. But you’ll also have breakthroughs when you solve a problem and feel a buzz of excitement at seeing your code work. The best way to keeping coding fun is to take on challenges that suit you. If a project is too easy you’ll get bored; if it’s too hard you’ll lose interest. Never be afraid to fiddle, tinker, experiment, and break the rules—let your curiosity lead you. But most of all, remember to have fun!

218 R E F E R E N C E Glossary algorithm call event GUI A set of step-by-step To use a function in a Something a computer The GUI, or graphical user instructions followed program. program can react to, such interface, is the name for when performing a as a key being pressed or the buttons and windows task: for example, by a compression the mouse being clicked. that make up the part of computer program. A way of making data the program you can see smaller so that it takes execute and interact with. ASCII up less storage space. See run. “American Standard hacker Code for Information computer network file A person who breaks Interchange”—a code used A way to link two or more A collection of data stored into a computer system. for storing text characters computers together. with a name. “White hat” hackers work as binary code. for computer security container float companies and look for binary code A part of a program A number with a decimal problems in order to fix A way of writing numbers that can be used to point in it. them. “Black hat” hackers and data that uses only store a number of break into computer 0s and 1s. other data items. function systems to cause harm or A piece of code that does to make profit from them. bit data part of a larger task. hardware A binary digit—0 or 1. Information, such as gate The physical parts of a The smallest unit of text, symbols, and Used by computers to computer that you can digital information. numerical values. make decisions. Gates see or touch, such as wires, use one or more input the keyboard, and the Boolean expression debug signals to produce an display screen. A question that has only To look for and correct output signal, based on two possible answers, such errors in a program. a rule. For example, “AND” hexadecimal as “true” and “false”. gates produce a positive A number system based on debugger output only when both 16, where the numbers 10 branch A program that checks input signals are positive. to 15 are represented by A point in a program where other programs for errors Other gates include “OR” the letters A to F. two different options are in their code. and “NOT”. available to choose from. index number directory GPU A number given to an bug A place to store files to A graphics processing item in a list. In Python, An error in a program’s keep them organized. unit (GPU) allows images the index number of the code that makes it behave to be displayed on a first item will be 0, the in an unexpected way. encryption computer screen. second item 1, and so on. A way of encoding data so byte that only certain people graphics input A unit of digital can read or access it. Visual elements on a Data that is entered into information that screen that are not text, a computer: for example, contains eight bits. such as pictures, icons, from a microphone, and symbols. keyboard, or mouse.

219G L O S S A R Y integer memory programming language statement Any number that does not A computer chip inside a A language that is used The smallest complete contain a decimal point computer that stores data. to give instructions to instruction a programming and is not written as a a computer. language can be broken fraction (a whole number). module down into. A section of code that random interface performs a single part A function in a string The means by which of an overall program. computer program that A series of characters. the user interacts with allows unpredictable Strings can contain software or hardware. operator outcomes. Useful when numbers, letters, or A symbol that performs creating games. symbols, such as a colon. IP address a specific function: for A series of numbers that example, “+” (addition) run syntax makes up a computer’s or “-” (subtraction). The command to make The rules that determine individual address when a program start. how a program must be it is connected to OS structured in order for it the Internet. A computer’s operating server to work properly. system (OS) provides the A computer that stores files library basis for other programs accessible via a network. trojan A collection of functions to run, and connects A piece of malware that that can be reused in them to hardware. single-step pretends to be another other projects. A way of making a piece of software to output computer program run trick the user. loop Data that is produced by one step at a time, to Part of a program that a computer program and check that each step is tuple repeats itself (to prevent viewed by the user. working properly. A list of items separated by the need for the same commas and surrounded piece of code to be typed port socket by brackets. out multiple times). A series of numbers The combination of an used by a computer as IP address and a port, Unicode machine code the “address” for a which lets programs send A universal code used by The basic language specific program. data directly to each other computers to represent understood by computers. over the Internet. thousands of symbols Programming languages processor and text characters. must be translated into A type of electronic chip software machine code before the inside a computer that The programs that run on variable processor can read them. runs programs. a computer and control A named place where you how it works. can store information malware program that can be changed. sprite Software that is designed A set of instructions that a A movable object. virus to harm or disrupt a computer follows in order A type of malware that computer. Malware is short to complete a task. works by multiplying for “malicious software”. itself to spread between computers.

220 R E F E R E N C E Index Page numbers in bold refer bits 183, 189, 218 in strings 114 algorithms 16, 17 to main entries. black-hat hackers 213 Unicode 185 bad programs 212–13 blank lines 117 Chef 199 essential 190–1 A blocks circles, drawing 157, 158 experimenting with 19 circuits, computer 187, 188, 189 how they work 15 Ada 18 colored 31 clicking, and events 44, 66, 162 uses of 14 addition 52, 102, 112 connecting 18 clock pulse 188 computers Adobe Flash 25 creating 72–3 coordinates deconstructing 217 AI see Artificial Intelligence defining 72, 73 drawing with 158 invention of 201 algorithms 16, 17, 150–1, 218 functions of 31 and location 168 main parts of 180–1 Allen, Paul 200 help with 83 and movement 166 mini 214–15 ALU see arithmetic logic unit with inputs 73 in Python 157 supercomputers 203 American Standard Code for programming 22 in Scratch 56–7 console games 198 types of 31 COBOL 199 consoles 14, 204 Information Interchange see blocks palette 27, 31, 32, 35, 38, code windows 92, 93, 106–7 containers 134, 218 ASCII 50 errors in 94 “continue” keyword 127 “and” block/operator 63, 103, bomb disposal 203 coders 14, 15 “Control” blocks 31, 65, 68 118, 119 Boole, George 186 becoming a coder 18–19 control unit 180 AND gate 186 Boolean expressions 62, 63, 64, becoming a master controls, game 174, 205 Android operating system 198, 65, 111, 118–19, 120, 218 costumes 40–1 207 botnets, zombie 213 programmer 216–17 and movement 23, 40, 41 anti-malware software 213 brackets famous 200–1 random 61 antivirus programs 213 errors 94 and games 204 Roll the dice project 60–1 apostrophes 115 in lists 128, 129 think like a computer 16–17 and speech bubbles 41 Apple Mac in tuples 134 coding switching 34, 40, 41 file management 193 using 112, 119 clear 143 cryptography 202 operating system 190, 207 brain, training 216 computer programs 14–15 CSS (Cascading Style Sheets) 208 programming languages 198 branches/branching 65, 99, 100, reading 176, 216 cursor tools 26 Python 3 on 88, 90 120–1, 218 what is coding? 14–19 Scratch on 25 breaks, inserting in loops 126–7 coding clubs 82, 207 D apps, making 206–7 Brin, Sergei 201 coding contests 217 Arduino 214, 215 broadcast blocks 70–1, 77 colors data 218 arithmetic logic unit (ALU) 181 browser windows 210, 211 adding to shapes 159 and functions 131 arrow keys 163, 166 Bubble blaster project 164–75 changing 60, 160 input 180 Artificial Intelligence (AI) 203, bugs 148–9, 177, 207, 218 mixing 156 output 181 205 buttons in Python 156–7 secret 202 ASCII 184, 218 creating 152, 154–5 selecting 156 sending via Internet 194, 195 audio output 181, 215 labelling 155 commands theft 213 linking to events 162 Python and Scratch B bytes (B) 183, 192, 218 “Data” blocks 31, 50 compared 102–5 data storage Babbage, Charles 200 C commas backgrounds/backdrop 23, 26 in files 192–3 C 18, 198 in lists 128 memory 180, 181, 188, 189 changes to 45 C++ 198 in tuples 134 in variables 50 selecting from library 33, 74 calculations 180, 181, 189 comments, adding 143 data types switching 41 comparison blocks/operators converting 111 backpack, Scratch 82 in Python 112 62–3, 118–19 mixed 111 banking 199, 202 in Scratch 52–3 compass 39 spotting 111 bases 182–3 supercomputers 203 compilers 191 tuples and dictionaries 134–5 BASIC 199 calling functions 104, 139, 218 components, computer 181, 217 debugging 148–9, 174, 177, 207, battery, computer 181 cameras 215 compression 202, 218 218 beats 59 canvas 157, 158 computer circuits 187, 188, 189 decimal system 182 Berners-Lee, Tim 201 cars 14 computer games see games decisions binary code/signals 15, 182–3, characters computer languages see and branches 64–5 184, 185, 195, 218 between outputs 117 programming languages flowcharts 141 numbering in strings 115 computer programmers see logic gates 186–7 coders computer programs 14–15

I N D E X 221 dice simulator 155 floats 110, 218 H connection to 19 dictionaries 135 flowcharts 141, 146 programming for 208–9 direction 39 folders 193 hackers 213, 218 Internet browsers 209 directories 193, 218 “for” loops 122, 124 hardware 15, 181, 191, 218 Internet Protocol 194 directory trees 193 “forever” block 23, 31, 32, 33, 38, interpreters 191 division 52, 102, 112 programming 198 inverters 186 domain names 194 39, 46, 47, 125 hexadecimal 156, 183, 185, 218 iOS devices 198 drawing forever loop 46, 47, 69, 103, 125, high-level languages 191 IP addresses 194, 195, 219 Hopper, Grace 200 on a canvas 157, 165 133 HTML (HyperText Markup J with coordinates 158 Fortran 199 pens and turtles 48–9, 122, full stops 117 Language) 208, 209, 210 Java 18, 198 functions 72, 130–1, 132–3, 218 JavaScript 18, 198, 208, 209 152 I Drawing machine project 140–7 calling 104, 130, 139 using 210–11 drums 59 getting data back from 131 IDLE JPEGs 193 making 130 code and shell windows 106–7 E passing data to 131 color codes 107 K using and naming 143 and errors 148 educational apps 206 and variables 138–9 how it works 93 keyboard electrical signals 195 and installation of Python events 44, 66, 162, 163, 211 “elif” command 121 G 89, 90, 91 input function 116, 162, 163, “else-if” command see “elif” what is IDLE? 88 180 gadgets 215 working in 92–3, 209 command Game Boy 201 keys, dictionaries 135 emails game engines 205 “if” block/command 64, 120 kilobytes (KB) 183, 192 game logic 205 “if-elif-else” command 121 spam 213 games 14, 204–5 “if-else” command 120 L websites 198, 208 “if-then” block/command 64, 66, encryption 202, 218 customizing 81 laptops 181 “end” label 117 improving 174 67, 103 latch circuits 189 errors 94–5 in JavaScript 209 “if-then-else” block/command letter commands 141 finding and fixing 148–9 making with Python 177 level designers 204 Escape the dragon! project 32–7 for mobile devices 206 64, 65, 76, 103 libraries 219 event handlers 166, 211 online 195 “in” operator 119 events 211, 218 random numbers in 53 indents 98 building your own 176 reacting to 162–3 see also projects index numbers 115, 128, 218 help and documentation “Events” blocks 31, 32, 44–5 Gates, Bill 200 infinite loops 125 EXCLUSIVE OR gate 187 gates, logic 186–7, 218 input 153 experimenting Ghost game project 96–9 importing 153 with coding 19 gigabytes (GB) 189, 192 blocks with 73 light, data transmission as with Python 176–7 global variables 138, 139 devices 162, 180, 189 pulses of 195 with Scratch 82–3 GNU/Linux operating system 201 logic gates 186–7 Linux 88, 201 Google 86, 201, 217 program 31, 100, 101, 106, lists F GPU 218 adding/deleting items 55, 105, graphic designers 204 116, 180, 218 Facebook 201 graphical user interface “input()” function 101, 130 128, 129, 169 false see true or false see GUI insertion sort 150 combining 129 fiberoptic cables 195 graphics 218 installation commands 105 file browsers 190 changing 160–1 copying 137 files 218 color and coordinates 156–7 Python 3 88–91 creating 55, 105 effects 43, 152, 153 Scratch 24–5 in loops 129 compressing 202 games 205 instruments, musical 59 playing with 55 corruption 213 making shapes 158–9 integers 110, 219 putting tuples in 134 managing 193 graphics processing unit Integrated DeveLopment in Python 128–9, 132–3 properties 192 see GPU Environment see IDLE in Scratch 54–5 sizes 192 grid, x and y 56, 158 interface using 55, 129, 167 storing data in 192–3 GUI 154–9, 218 GUI 154–5 in variables 136–7 firewalls 213 Scratch 26–7, 49 user 140, 146–7, 219 Internet 194–5 connecting to other computers via 152

222 R E F E R E N C E local variables 138, 139 mini computers 214–15 O from the past 199 logic circuits 187, 188, 189 Miyamoto, Shigeru 201 and interpreters 191 logic errors 148 mobile phones 14, 204, 215 Objective-C 198 learning new 217 logic gates 186–7, 188, 189 Ook 199 popular 198 logical operators 118–19 apps 206–7 open source movement 201 Python and Scratch commands LOGO 49 modules 219 operating systems (OS) 25, “Looks” blocks 31, 40, 42–3 compared 102–5 loop blocks 46 importing 153 88–91, 92, 190–1, 207, 219 text-based 86 loops 100, 103, 219 Standard Library 152 operators 219 weird 199 Monkey mayhem project 74–81 programs see computer complex 68–9 motherboard 181 blocks 31, 52, 53 programs with conditions 104 “Motion” blocks 31, 32, 33, 34, 36, logical 118–19 projects 11, 23 escaping 126–7 38–9, 57, 75 “or” block/operator 63, 103, 118 Bubble blaster 164–75 “for” 122, 124 motion detector, webcam 45 OR gate 187 Drawing machine 140–7 forever 46, 47, 69, 103, 125 mouse OS see operating systems Escape the dragon! 32–7 in JavaScript 211 control 25 output Ghost game 96–9 lists in 129 events 162, 211 and branching 120–1 Monkey mayhem 74–81 main 99, 168, 169, 171 input function 180, 189 devices 180, 181, 189 remixing existing 82 nested 69, 123 mouse-pointer logic gates 186–7 Roll the dice 60–1 in Python 122–7, 133 coordinates 56 program 31, 92, 100, 101, Silly sentences 132–3 in Scratch 46–7, 68–9 following 69 PS4 204 simple 46–7 pointing toward 32, 33, 36 106, 108, 116–17, 180–1 pseudocode 143, 144, 147 skipping 124, 127 movement Pygame 153, 177 stopping 125 coordinates 57 P Python 19, 83, 84–177 variable 123 and costumes 23, 40, 41 algorithms 150–1 while 124–5 with keys 66, 163, 166 packets 194, 195 ASCII in 184 Lovelace, Ada 200 and “Sensing” blocks 66, 67 Page, Larry 201 Booleans 111 low-level languages 191 sprites 22, 23, 38–9, 57 painting area 60, 61 branching 120–1 Mpegs 193 passwords, theft of 213 Bubble blaster project 164–75 M multiplication 52, 102, 112 paths 193 bugs and debugging 148–9 music “Pen” blocks 31, 48–9, 87, 107 code structure 98–9 Mac see Apple Mac adding 37, 79 Peters, Tim 151 color and coordinates 156–7 Mac OS X 190 files 192, 193, 202 photograph files 193 color codes 107 machine code 188, 191, 219 making your own 59 Pi 214 different versions of 177 Malbolge 199 playing 59 pictures, files 192, 193 Drawing machine project malware 212–13, 219 tempo 59 Piet 199 Math module 152 mutable/immutable objects pilots 205 140–7 math 129 Pixar 86 errors 94–5 pixels 156 escaping loops 126–7 in Python 102, 112–13 N player’s name 50 functions 130–1, 132–3 in Scratch 52–3, 102 PNGs 193 Ghost game project 96–9 MATLAB 18 name errors 95 pop-up boxes/windows 146, harder commands 104–5 medicine 203 NASA 86 input and output 116–17 megabytes (MB) 183, 189, 192 negative numbers 56, 57 209, 210 installing 88–91 memory 180–1, 188–9, 190, nested loops 47, 69, 123 ports 195, 219 introducing IDLE 92–3 192, 219 network adaptors 181, 195 position libraries 152–3 messages networks, computer 152, lists 128–9, 132–3 reacting to 70 coordinates 56–7 lists in variables 136–7 sending and receiving 70 194, 218 random 43, 57 loops in 122–7, 133 microphones, and events 44, 45 nibbles 183 “print()” function 87, 101, 102, making decisions 118–19 Microsoft 200 NOT gate 186 108, 109, 116, 117, 130 making games with 177 Microsoft Windows notes, musical 59 printers 181 making shapes 158–9 file management 193 numbers processors 100, 101, 180–1, making windows 154–5 operating system 190, 207 188–9, 190, 203, 219 math in 112–13 Python 3 on 88, 89 binary and bases 182–3 program flow 100–1 numbers in 110 Scratch on 25 comparing 62, 118 programming languages 15, 18, print in 87 millennium bug 199 data types in Python 110 19, 22, 49, 83, 198–9, 219 program flow 100–1 random 53, 104, 113, 152, 155 conversion into machine code reacting to events 162–3 188 first 200

I N D E X 223 saving work 88 home-built 215 simple commands 102–3 sound designers 204 and Scratch 87, 101, 102–5, Roll the dice project 60–1 simple loops 46–7 sound library 79 rotation software 24 sounds 22, 23 124, 125 special effects 42–3 scripts 101 styles 38 sprites 28–9 adding to program 58–9, 79 shell and code windows 92, tools 61 strings and lists 54–5 detectors 45 routers 194, 195 true or false 62–3 in games 205 93, 106–7 Ruby 18 typical programs 23 playing 58 shortcuts 171 running understanding 22 selecting from library 37, 58 Silly sentences project 132–3 programs 23, 102, 106 variables 50–1, 108 volume control 58 simple commands 102–3 scripts 30 versions of 25 spam 213 sorting in 151 runtime errors 148 and webcams 45 speakers 181 strings in 110, 114–15, 117 website 24, 82 speech bubbles 22, 28, 87, 101 tuples and dictionaries 134–5 S what is Scratch? 18, 22–3 adding 41, 161 turtle graphics 87 screens 181 conversations 71 types of data 110–11 saving your work 11 scripts 22, 23 speed, setting 51, 77 Unicode in 185 in Python 88, 93, 106, 107 building 27 “split()” function 144 variables 99, 101, 108–9, 116 in Scratch 24, 25, 33 and colored blocks 30–1 sprites 22, 23, 28–9, 39, 219 variables and functions 138–9 flow of 30 adding graphic effects 43 website 89 saying things (in Python) 161 pausing 69 adding more 76–7, 80 what is Python? 19, 86–7 score 50, 79, 99, 172–3 in Python 101 adding sounds 58–9 what next? 176–7 scoreboards 172 repeating 68 changing size 43 while loops 124–5 Scratch 20–83 running 30 changing time or speed 35, 51 in Scratch 30–1, 101 coordinates 56–7 Q account 24 and sprites 28 collisions 67 adding sounds 58–9, 79 stopping 30, 68 communication between questions backpack 82 testing 30 asking 54 blocks 30–1, 72–3 scripts area 27 70–1 combining 63 coordinates 56–7 scripts tab 27 controlling 31, 66 true or false 62–3 complex loops 68–9 scriptwriters 204 copying or deleting 29 costumes 40–1 SD cards 215 creating and editing 29, 34, 36 quote marks creating blocks 72–3 secret data 202 designing your own 39 errors 94 decisions and branches 64–5 selection sort 151 direction 39 in lists 128 Escape the dragon! project “Sensing” blocks 31, 34, 36, 51, and events 44–5 in strings 110, 114, 116 65, 66–7, 75 hiding and showing 42 32–7 separators 117 in the interface 28 R events 44–5 servers 219 movement 22, 23, 38–9, 57, experimenting with 82–3 shapes radio waves 195 harder commands 104–5 adding color 159 66–7 RAM 189 help menu 83 drawing 140 naming 29 “randint()” function 98, 99, 101, hide and seek 42–3 making 158–9 pen tools 48–9 installing and launching 24–5 moving 160 renaming 29 104, 113, 130, 153, 155 interface 26–7, 49 naming 160 rotation styles 38 Random Access Memory lists 55 shell windows 92, 93, 106–7, 116 and scripts 28 make some noise 58–9 errors in 95 selecting from library 34, 36, see RAM making things move 38–9 silicon chips 188, 189 Random module 152, 153, 157 math in 52–3 Silly sentences project 132–3 39, 75, 76 random numbers 53, 104, 113, menu and tools 26 skipping, in loops 127 and “Sensing” blocks 66–7 and microphones 45 slicing 115 sprite list 27 152, 155 Monkey mayhem project smartphones 206 turtle graphics 49 random positions 43, 57 social apps 206 and variables 35, 50–1 Raspberry Pi 25, 214 74–81 Socket module 152 what they can do 28 reacting to events 162–3 pens and turtles 48–9, 87 sockets 195, 219 square roots 53 readable code 133 and Python 87, 102–5, 124, 125 software 14, 15, 219 stage 23, 25, 27 remainders 53 and Python’s Ghost game 101 sorting algorithms 150–1 Standard Library modules 152 repeat loops 46, 122, 211 Roll the dice project 60–1 “Sound” blocks 31, 58–9 stop button 30 “repeat until” block 68, 76, 77, scripts and colored blocks stopping programs 102 strategy games 205 78, 124 30–1, 101 strings 219 rewriting code 217 sending messages 70–1 adding 114 robots 16, 203, 217 sensing and detecting 66–7

224 R E F E R E N C E assigning 108 turtle graphics 49, 87, 105, 107 read-only 51 X comparing 63, 118, 119 commands 105, 145 results in 52 creating 114 Drawing machine project in Scratch 50–1, 108 x and y coordinates 56, 57, 157, joining 105 140–7 splitting tuples into 134 158, 166, 168 length of 114 and loops 122 strings in 114 operators 119 using 51, 109 Xbox One 204 in Python 110, 114–15, 117 Turtle module 152, 176 video files 192, 193 in Scratch 54–5 video games 204–5 Y separating 117 U writing 153 subprograms see functions viruses 212–13, 219 Yokoi, Gunpei 201 subtraction 52, 102, 112 Ubuntu visual output 181 supercomputers 203 file management 193 volume control 58 Z surgeons 205 Python 3 on 88, 91 von Neumann, John 180 symbols, choice of 143 Scratch on 25 zombie botnets 213 syntax 219 W Zuckerberg, Mark 201 errors 94, 148 Unicode 185, 219 upper/lower case 94 washing machines 14 T USBs 215 watches 206 user interface 140, 146–7, 219 wearable technology 206 tablets 25, 206 weather forecasting 199, 203, tabs 26, 27 V teleporting 43 206, 215 television 215 values web browsers 86, 195, 198 tempo 59 assigning to variables 108, web servers 198 terabytes (TB) 192 109, 113, 118, 136 webcams, and events 44, 45 testers, game 204 changing 136 websites text editors 88 in dictionaries 135 text files 193 and functions 131 construction 208–9 text messages 14 email 198, 208 text-based programming variables 35, 219 interactive 198, 208, 210, 211 assigning a value to 108, 109, Python 89 languages 86 113, 118, 136 Scratch 24, 82 time limit 172–3 changing contents of 109 while loops 124–5 Time module 152 comparing 62, 63, 118 white-hat hackers 213 Tkinter module 152, 154–5, 156, creating 50, 54, 77, 102, 108 Wikipedia 201 deleting 51 Windows see Microsoft Windows 157, 158, 159, 162, 165, 176 and functions 138–9 windows transistors 188 global 138, 139 code and shell 92, 93, 106–7 travel apps 206 lists in 136–7 making 152, 154–5, 165 Trojans 212, 213, 219 local 138, 139 word processing 86 true or false 62–3, 64, 111, loop variables 123 words, comparing 63 naming 50, 109, 143 World Wide Web 201 118–21, 125 in Python 99, 101, 108–9, 116, worms 212, 213 tuples 134, 219 138–9 Turing, Alan 200 Acknowledgments DORLING KINDERSLEY would like to thank: Max Albert for technical Scratch is developed by the Lifelong Kindergarten Group at MIT assistance on the US edition; Vicky Short, Mandy Earey, Sandra Perry, Media Lab. See http://scratch.mit.edu and Tannishtha Chakraborty for their design assistance; Olivia Stanford for her editorial assistance; Caroline Hunt for proofreading; Python is copyright © 2001–2013 Python Software Foundation; All Helen Peters for the index; and Adam Brackenbury for creative Rights Reserved. technical support. DORLING KINDERSLEY INDIA would like to thank: Kanika Mittal for design assistance; Pawan Kumar for pre-production assistance; and Saloni Singh for editorial management of the jackets team.