Coding All-in-One For Dummies®
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ISBN 978-1-119-36302-6 (pbk); 978-1-119-36303-3 (epub); 978-1-119-36305-7 (epdf)
The ability to read, write, and understand code has never been more important, useful, or lucrative than it is today. Computer code has forever changed our lives. Many people can’t even make it through the day without interacting with something built with code. Even so, for many people, the world of coding seems complex and inaccessible. Maybe you participated in a tech-related business meeting and did not fully understand the conversation. Perhaps you tried to build a web page for your family and friends, but ran into problems displaying pictures or aligning text. Maybe you’re even intimidated by the unrecognizable words on the covers of books about coding, words such as HTML, CSS, JavaScript, Python, or Ruby.
If you’ve previously been in these situations, then Coding All-in-One For Dummies is for you. This book explains basic concepts so you can participate in technical conversations and ask the right questions, and it goes even further than Coding For Dummies by covering additional topics in data science, machine learning, and coding careers. Don’t worry — this book assumes you’re starting with little to no previous coding knowledge, and I haven’t tried to cram every possible coding concept into these pages. Additionally, I encourage you here to learn by doing and by actually creating your own programs. Instead of a website, imagine that you want to build a house. You could spend eight years studying to be an architect, or you could start today by learning a little bit about foundations and framing. This book kick-starts your coding journey today.
The importance of coding is ever-increasing. As author and technologist Douglas Rushkoff famously said, “program or be programmed.” When humans invented languages and then the alphabet, people learned to listen and speak, and then read and write. In our increasingly digital world, it’s important to learn not just how to use programs but also how to make them. For example, observe this transition in music. For over a century, music labels decided what songs the public could listen to and purchase. In 2005, three coders created YouTube, which allowed anyone to release songs. Today more songs have been uploaded to YouTube than have been released by all the record labels combined in the past century.
Accompanying this book are examples at www.codecademy.com, whose exercises are one of the easiest ways to learn how to code without installing or downloading anything. The Codecademy website includes examples and exercises from this book, along with projects and examples for additional practice.
This book is designed for readers with little to no coding experience, and gives an overview of programming to non-programmers. In plain English, you learn how code is used to create web programs, who makes those programs, and the processes they use. The topics covered include
As you read this book, keep the following in mind:
http://tinyletter.com/codingfordummies.I do not make many assumptions about you, the reader, but I do make a few.
I assume you don’t have previous programming experience. To follow along, then, you only need to be able to read, type, and follow directions. I try to explain as many concepts as possible using examples and analogies you already know.
I assume you have a computer running the latest version of Google Chrome. The examples in the book have been tested and optimized for the Chrome browser, which is available for free from Google. Even so, the examples may also work in the latest version of Firefox. Using Internet Explorer for the examples in this book, however, is discouraged.
I assume you have access to an Internet connection. Some of the examples in the book can be done without an Internet connection, but most require one so that you can access and complete the exercises on www.codecademy.com.
For the books on data analysis and machine learning, I assume you are able to download and install the Python programming language and associated programming libraries, both of which are available for free. I also assume you have some math background and understand how algorithms work.
Here are the icons used in the book to flag text that should be given extra attention or that can be skipped.
This icon flags useful information or explains a shortcut to help you understand a concept.
This icon explains technical details about the concept being explained. The details might be informative or interesting, but are not essential to your understanding of the concept at this stage.
Try not to forget the material marked with this icon. It signals an important concept or process that you should keep in mind.
Watch out! This icon flags common mistakes and problems that can be avoided if you heed the warning.
A lot of extra content that you won’t find in this book is available at www.dummies.com. Go online to find the following:
The source code for the examples in this book: You can find it at
www.dummies.com/go/codingaiodownloads.
The source code is organized by chapter. The best way to work with a chapter is to download all the source code for it at one time.
The links to the Codecademy and other exercises: You can find these at
www.dummies.com/go/codingaiolinks.
Cheat Sheet: You can find a list of common HTML, CSS, and JavaScript commands, among other useful information.
To view this book’s Cheat Sheet, simply go to www.dummies.com and search for “Coding For Dummies All-in-One Cheat Sheet” in the Search box.
Updates: Code and specifications are constantly changing, so the commands and syntax that work today may not work tomorrow. You can find any updates or corrections by visiting
http://tinyletter.com/codingfordummies.
All right, now that all the administrative stuff is out of the way, it’s time to get started. You can totally do this. Congratulations on taking your first step into the world of coding!
Book 1
Contents at a Glance
Chapter 1
IN THIS CHAPTER
Seeing what code is and what it can do
Touring your first program using code
Understanding programming languages used to write code
“A million dollars isn’t cool, you know what’s cool? A billion dollars.”
— SEAN PARKER, The Social Network
Every week the newspapers report on another technology company that has raised capital or sold for millions of dollars. Sometimes, in the case of companies like Instagram, WhatsApp, and Uber, the amount in the headline is for billions of dollars. These articles may pique your curiosity, and you may want to see how code is used to build the applications that experience these financial outcomes. Alternatively, your interests may lie closer to work. Perhaps you work in an industry in decline, like print media, or in a function that technology is rapidly changing, like marketing. Whether you are thinking about switching to a new career or improving your current career, understanding computer programming or “coding” can help with your professional development. Finally, your interest may be more personal — perhaps you have an idea, a burning desire to create something, a website or an app, to solve a problem you have experienced, and you know reading and writing code is the first step to building your solution. Whatever your motivation, this book will shed light on coding and programmers, and help you think of both not as mysterious and complex but approachable and something you can do yourself.
In this chapter, you will understand what code is, what industries are affected by computer software, the different types of programming languages used to write code, and take a tour of a web app built with code.
Computer code is not a cryptic activity reserved for geniuses and oracles. In fact, in a few minutes you will be writing some computer code yourself! Most computer code performs a range of tasks in our lives from the mundane to the extraordinary. Code runs our traffic lights and pedestrian signals, the elevators in our buildings, the cell phone towers that transmit our phone signals, and the space ships headed for outer space. We also interact with code on a more personal level, on our phones and computers, and usually to check email or the weather.
Computer code is a set of statements, like sentences in English, and each statement directs the computer to perform a single step or instruction. Each of these steps is very precise, and followed to the letter. For example, if you are in a restaurant and ask a waiter to direct you to the restroom, he might say, “head to the back, and try the middle door.” To a computer, these directions are so vague as to be unusable. Instead, if the waiter gave instructions to you as if you were a computer program he might say, “From this table, walk northeast for 40 paces. Then turn right 90 degrees, walk 5 paces, turn left 90 degrees, and walk 5 paces. Open the door directly in front of you, and enter the restroom.” Figure 1-1 shows lines of code from the popular game, Pong. Do not worry about trying to understand what every single line does, and don’t feel intimated. You will soon be reading and writing your own code.
FIGURE 1-1: Computer code from the game Pong.
One rough way to measure a program’s complexity is to count its statements or lines of code. Basic applications like the Pong game have 5,000 lines of code, while more complex applications like Facebook currently have over 10 million lines of code. Whether few or many lines of code, the computer follows each instruction exactly and effortlessly, never tiring like the waiter might when asked the hundredth time for the location of the restroom.
Be careful of only using lines of code as a measure for a program’s complexity. Just like when writing in English, 100 well written lines of code can perform the same functionality as 1,000 poorly written lines of code.
If you’ve never written code before, now is your chance to try! Go to http://csedweek.org/learn, where you will see a beginner student experience, scroll down the page, and click the tile labeled “Write Your First Computer Program,” the link with the Angry Birds icon, as shown in Figure 1-2. This tutorial is meant for those with no previous computer programming experience, and it introduces the basic building blocks used by all computer programs. You can also click the tile labeled “Star Wars: Building a Galaxy with Code.” The most important takeaway from these tutorials is to understand that computer programs use code to literally and exactly tell the computer to execute a set of instructions.
FIGURE 1-2: Write your first computer program with a gamelike tutorial using Angry Birds.
Computer Science Education Week is an annual program dedicated to elevating the profile of computer science during one week in December. In the past, President Obama, Bill Gates, basketball player Chris Bosh, and singer Shakira, among others, have supported and encouraged people from the United States and around the world to participate.
Coding can be used to perform tasks and solve problems that you experience every day. The “everyday” situations in which programs or apps can provide assistance continue to grow at an exponential pace, but this was not always the case. The rise of web applications, Internet connectivity, and mobile phones inserted software programs into daily life, and lowered the barrier for you to become a creator, solving personal and professional problems with code.
In 2011, Marc Andreessen, creator of Netscape Navigator and now venture capitalist, noted that “software is eating the world.” He predicted that new software companies would disrupt existing tech companies at a rapid pace. Traditionally, code-powered software used on desktops and laptops had to first be installed, and then you had to supply data to the program. However, three trends have dramatically increased the use of code in everyday life:
www.hotmail.com to instantly check their email without worrying about installation issues or software incompatibility. Web applications increased consumer appetite to try more applications, and developers in turn were incentivized to write more applications.The combination of these trends have created software companies that have upended incumbents in almost every industry, especially those typically immune to technology. Here are some notable examples:
FIGURE 1-3: Airbnb booked 5 million nights after 3.5 years, and its next 5 million nights 6 months later.
Coding can be useful in the workplace as well. Outside the technology sector, coding in the workplace is common for some professions like financial traders, economists, and scientists. However, for most professionals outside the technology sector, coding is just beginning to penetrate the workplace, and gradually starting to increase in relevance. Here are areas where coding is playing a larger role on the job:
Sales: The sales process always starts with leads. Salespeople who code retrieve their own leads from web pages and directories and then sort and quantify those leads.
Retrieving information by copying text on web pages and in directories is referred to as scraping.
Using code built by others and coding in the workplace may cause you to think of problems you personally face that you could solve with code of your own. You may have an idea for a social network website, a better fitness app, or something new altogether. The path from idea to functioning prototype used by others involves a good amount of time and work, but might be more achievable than you think. For example, take Coffitivity, a productivity website that streams ambient coffee shop sounds to create white noise. The website was created by two people who had just learned how to program a few months prior. Shortly after Coffitivity launched, Time magazine named the website as one of 50 Best Websites of 2013, and the Wall Street Journal also reviewed the website. While not every startup or app will initially receive this much media coverage, it can be helpful to know what is possible when a solution really solves a problem.
Having a goal, like a website or app you want to build, is one of the best ways to learn how to code. When facing a difficult bug or a hard concept, the idea of bringing your website to life will provide the motivation you need to keep going. Just as important, do not learn how to code to become rich and famous, as the probability of your website or app becoming successful is largely due to factors out of your control.
The characteristics that make a website or app addictive are described using the “hook model” at http://techcrunch.com/2012/03/04/how-to-manufacture-desire. Products are usually made by companies, and the characteristics of an enduring company are described at http://www.sequoiacap.com/grove/posts/yal6/elements-of-enduring-companies, which is based on a review of companies funded by Sequoia, one of the most successful venture capital firms in the world and an early investor in Apple, Google, and PayPal.
Code comes in different flavors called programming languages. Some popular programing languages are shown in Figure 1-4.
FIGURE 1-4: Some popular programming languages.
You can think of programming languages as being similar to spoken languages because they both share many of the same characteristics, such as the following:
Despite these similarities, programming languages also differ from spoken languages in a few key ways:
One creator: Unlike spoken languages, programming languages can be created by one person in a short period of time, sometimes in just a few days.
Popular languages with a single creator include JavaScript (Brendan Eich), Python (Guido van Rossum), and Ruby (Yukihiro Matsumoto).
One way to classify programming languages is as either low-level languages or high-level languages. Low-level languages interact directly with the computer processor or CPU, are capable of performing very basic commands, and are generally hard to read. Machine code, one example of a low-level language, uses code that consists of just two numbers, 0 and 1. Figure 1-5 shows an example of machine code. Assembly language, another low-level language, uses keywords to perform basic commands, such as read data, move data, and store data.
FIGURE 1-5: Machine code consists of 0s and 1s.
By contrast, high-level languages use natural language, so it is easier for people to read and write. Once code is written in a high-level language, like C++, Python, or Ruby, an interpreter or compiler must translate this high-level language into low-level code that a computer can understand.
Interpreted languages are considered more portable than compiled languages, while compiled languages execute faster than interpreted languages. However, the speed advantage compiled languages have is starting to fade in importance as improving processor speeds make performance differences between interpreted and compiled languages negligible.
High-level programming languages like JavaScript, Python, and Ruby are interpreted. For these languages, the interpreter executes the program directly, translating each statement one line at a time into machine code. High-level programming languages like C++, COBOL, and Visual Basic are compiled. For these languages, after the code is written, a compiler translates all the code into machine code, and an executable file is created. This executable file is then distributed via the Internet, CD-ROMs, or other media and run. Software you install on your computer, like Microsoft Windows or Mac OS X, are coded using compiled languages, usually C or C++.
Software accessible on websites is gradually starting to take over installed software. Think of the last time you downloaded and installed software for your computer — you may not even remember! Installed software like Windows Media Player and Winamp that play music and movies have been replaced with websites like YouTube and Netflix. Traditional installed word processor and spreadsheet software like Microsoft Word and Excel is starting to see competition from web software like Google Docs and Sheets. Google is even selling laptops called Chromebooks that contain no installed software, and instead rely exclusively on web software to provide functionality.
The remainder of this book focuses on developing and creating web software, not just because web software is growing rapidly but also because programs for the web are easier to learn and launch than traditional installed software.
With all this talk of programming, let us actually take a look at a web application built with code. Yelp.com is a website that allows you to search and find crowd-sourced reviews for local businesses like restaurants, nightlife, and shopping. As shown in Figure 1-6, Yelp did not always look as polished as it does today, but its purpose has stayed relatively constant over the years.
FIGURE 1-6: Yelp’s website in 2004 and in 2014.
Once you understand an app’s purpose, you can identify a few actionable tasks a user should be able to perform to achieve that purpose. Regardless of design, the Yelp’s website has always allowed users to do the following:
Successful web applications generally allow for completing only a few key tasks when using the app. Adding too many features to an app is called scope creep, which dilutes the strength of the existing features, and so is avoided by most developers. For example, it took Yelp, which has 30,000 restaurant reviews, exactly one decade after its founding to allow users to make reservations at those restaurants directly on its website.
Whether you’re using or building an app, have a clear sense of the app’s purpose.
Developers make strategic choices and decide which parts of the app to code themselves, and on which parts of the app to use code built by others. Developers often turn to third-party providers for functionality that is either not core to the business or not an area of strength. In this way, apps stand on the shoulders of others, and benefit from others who have come before and solved challenging problems.
Yelp, for instance, displays local listing reviews and places every listing on a map. While Yelp solicits the reviews and writes the code to display basic listing data, it is Google, as shown in Figure 1-7, that develops the maps used on Yelp’s website. By using Google’s map application instead of building its own, Yelp created the first version of the app with fewer engineers than otherwise would have been required.
FIGURE 1-7: Google maps used for the Yelp web application.
Chapter 2
IN THIS CHAPTER
Seeing the code powering websites you use every day
Understanding the languages used to make websites
Finding out how applications are created for mobile devices
“To think you can start something in your college dorm room … and build something a billion people use is crazy to think about. It’s amazing.”
— MARK ZUCKERBERG
Programming for the web allows you to reach massive audiences around the world faster than ever before. Four years after its 2004 launch, Facebook had 100 million users, and by 2012 it had over a billion. By contrast, it took desktop software years to reach even one million people. These days, mobile phones are increasing the reach of web applications. Although roughly 300 million desktop computers are sold every year, almost two billion mobile phones are sold in that time — and the number is steadily increasing.
In this chapter, you discover how websites are displayed on your computer or mobile device. I introduce the languages used to program websites and show you how mobile-device applications are made.