Lesson 16 -...

AOIT Principles of Information Technology

Lesson 14Introduction to Programming

Student Resources

Resource Description

Student Resource 14.1 Reading: Introduction to Computer Code

Student Resource 14.2 Defining Format: Programming Terms

Student Resource 14.3 Keyword Notes: How Programming Languages Work

Student Resource 14.4 Reading: How Programming Languages Work

Student Resource 14.5 Flowchart: Illustrating the Flow of Logic

Student Resource 14.6 Programming Assignment: JavaScript Program

Student Resource 14.7 Reading: The Software Development Process

Student Resource 14.8 Poster: The Software Development Life Cycle

Copyright © 2007–2013 National Academy Foundation. All rights reserved.

AOIT Principles of Information TechnologyLesson 14 Introduction to Programming

Student Resource 14.1

Reading: Introduction to Computer CodeAs you know, the number of tasks computers can perform often seems limitless. But computers aren’t built knowing how to perform these tasks. In fact, computer hardware without software telling it how to function isn’t of any use at all (unless what you need is a doorstop). Computers are stupid—they can do only what we tell them to do. You can see this firsthand any time you mistype an email address or URL. One typo will keep your mail from being delivered or keep you from finding your favorite website.

The problem, then, is that people need to be able to give computers very detailed sets of instructions, but the languages that people speak (for example, English or Spanish) are very different from the languages that computers understand. A computer’s microprocessor can only understand instructions made up of 0s and 1s. The earliest computer programming was done using a “language” of these numbers that the computer could understand, but it was clear that it would be much easier for the people programming computers if they could write instructions in something a bit more like human language.

What Is Computer Code?Computer code is a set of detailed instructions telling a computer’s CPU what to do.

When you purchase software programs, you usually receive them in their machine-language format. This means that your computer can execute (or run) the program, but humans can’t read machine language.

A programmer writes code using a particular programming language. By “language” we don’t mean a human language such as English. Instead, the term refers to any language that can be used to define a sequence of instructions, or commands, that can be translated for a computer to understand.

The form of a program written by the programmer is called source code. In other words, source code consists of program instructions in their original form. Human programmers can read source code.

Before the code can run, however, the computer must translate it into machine code, the language that the computer understands. Machine code consists of a series of 0s and 1s (also called binary code). That is the only language that a computer understands! Programmers use utility programs called interpreters and compilers to translate source code into machine code.




Defining Format: Programming Terms Student Names: Date:

Directions: Use the frame below to list the characteristics of the terms used in Student Resource 14.1, Reading: Introduction to Computer Code. A Defining Format frame can help you organize your thoughts about a particular topic’s characteristics. An example is provided here.

Term Category Characteristics

Email is a program that 1. Lets users send messages over the Internet

2. Delivers messages (“mail”) instantly

3. Can send messages at any time of day

Term Category Characteristics

Source code is a set of program instructions that

1.

2.

3.

Machine code is a set of program instructions that

1.

2.

3.

A compiler is a programming tool that 1.

2.

3.




Keyword Notes: How Programming Languages WorkStudent Name:_____________________________________________________ Date:_____________

Directions: Use the following template to take notes on Student Resource 14.4, Reading: How Programming Languages Work. There are five sections to the reading. After each section, write down the three words that you think will help you remember the most important information in that section. Then move on to the next section and write three more words about that section. Continue this pattern with each of the remaining sections. Based on your keywords, write a summary in the bottom box that includes the important points you observed for each of the sections. Remember that a summary is not a rewrite of the article. Focus only on the key points you need to remember.

Introduction Different Programming Languages

Programming Methods Choosing a Language

The Flow of a Program

Summary




Reading: How Programming Languages Work

IntroductionProgramming languages enable people to use familiar words and symbols to tell computers what to do in a way that the computers can understand. Just as a human language has its own grammar and vocabulary, so each programming language has rules for writing commands, and special words and symbols that do different things. If you want to write a program, you choose a programming language (for example, Python or Java) and use its rules and grammar to write instructions, called source code, for the computer. When you are finished, you use another piece of software to turn what you’ve written into something the computer can understand. That software can be either an interpreter or a compiler.

Programming, the process of creating computer code, can be compared to writing a cooking recipe. Programs do for computers what recipes do for cooks: they organize data and give instructions for carrying out tasks. Sometimes, these instructions are simply a sequence of unchanging steps. At other times, more complex methods are needed for doing analysis and arriving at decisions.

A typical program consists of a main module and many submodules, sometimes called functions or subroutines. These modules are stored as a collection of files. Large programs can contain thousands of individual files, each with a specific purpose. These programs divide big problems into smaller problems. They operate quickly to solve all the smaller problems until the work adds up to one complete solution.

Different Programming LanguagesThere are many different kinds of programming languages. The higher-level a language is, the more it resembles a natural language like English, and the less programmers need to directly concern themselves with the internal workings of the computer hardware.

Whether high level or low level, each language has its own set of detailed grammar, spacing, and punctuation rules, just like the rules in languages that people use to communicate with each other. These rules are called syntax. If one of these rules is broken in the program code, the result is a syntax error, because the computer cannot understand the instructions that were given.

The original programming language, machine language, is the language that a computer’s processor understands. A machine language consists of large sets of 0s and 1s. Programming in machine code is not as common as it used to be, but when you write code in a higher-level language, it is then turned into machine code by a compiler or an interpreter.

Assembler is a low-level language. It uses letters and words instead of numbers in its code, but an Assembler programmer still has to know a lot about how the computer’s hardware works. Different versions of Assembler are specific to different types of computers.

C and C++ are sometimes called mid-level languages. These languages have more easily understood terms that make the programmer’s job easier. In particular, C++ lets programmers do things that are difficult when using Assembler. A C or C++ programmer still needs to be aware of things like how the computer’s memory stores numbers and data. These languages are popular in part because they use a computer’s resources efficiently. They also have the advantage of being able to run on many different kinds of processors.

Java, Python, C#, Visual Basic.NET, and Perl are examples of the many high-level programming languages available today. Mid- and high-level languages use words and symbols to represent complex concepts simply. This allows a programmer to do more with less effort. Mid- and high-level languages also use familiar math symbols, like the plus and minus signs, to show computer operations. Programs



created with high-level languages can direct much more complex tasks than those created with low-level languages. Some high-level languages serve a specific purpose, like creating graphics, while others are very flexible and are considered general purpose. A programmer who needs to write code that will work well with several different operating systems may choose Python or Java. Someone who needs a language that is good at dealing with text may use Perl.

Programming MethodsAnother way to classify programming languages is by the methods they use to create the program code. For example, the basic element of procedure-oriented programming is the “procedure” or sequence of statements (also called a routine). Simply put, a procedural language tells the computer how a task is done using a step-by-step process. The earliest high-level computer languages (BASIC, COBOL, Pascal, and so on) were all procedural.

Newer languages made a true break from procedure-oriented programming and are considered nonprocedural. With nonprocedural languages, a programmer defines only what he or she wants the computer to do. It is not necessary to specify how the task should be done.

Object-oriented programming is organized around “objects” rather than actions. Objects can represent anything from human beings (described by names, addresses, and so on) to buildings, cars, icons on your computer’s desktop, and so on. Object-oriented programming is focused on the objects the programmer wants to manipulate rather than on the logic used to control them. Java, C#, Visual Basic.NET, and C++ are object-oriented languages. Some languages, like Python, have both procedural and object-oriented characteristics and capabilities, depending on how they are used.

Choosing a LanguageChoosing which programming language to use is important. Every language has advantages and disadvantages, so choosing the best language for a particular situation depends on a number of factors. To begin, a programmer should ask questions like these:

What do you need the program to do? (What type of process or problem are you facing?)

On what type of computer hardware will the program be run?

What kind of existing software needs to interact with the new program?

How experienced is the programmer?

How “steep” is the learning curve (that is, how difficult would it be for someone not familiar with a particular language to learn to use it effectively)?

How easy is it to make changes or find errors using a particular language?

Once you have the answers to these questions, you can begin to figure out which language is the easiest, most efficient, and/or the best suited for the job. For example, think about the following:

Fortran, a language for processing numerical data, doesn’t lend itself well to organizing large programs. Because of its limitations, Fortran is almost never used for new computer software development.

C++ is a powerful language that uses object-oriented features. It is also considered harder to learn than some other languages.

Java is often used to create applications for websites that will run on the site’s web server. Also, because Java was designed so that it would never be tied to any one platform, it’s a popular choice when developing programs that run on multiple operating systems.

Python and Perl are easy-to-learn, general-purpose, high-level languages that also have sophisticated capabilities and can operate as both procedural and object-oriented languages.



Visual Basic.NET, and C# are often used to develop programs for Windows-based computers.

The Flow of a ProgramPrior to creating the actual source code, a programmer may “map” the program, or a portion of it, by writing an algorithm (an instruction or set of instructions explaining how to solve a problem) and by illustrating it using a flowchart. A flowchart is a diagram that uses graphical symbols to illustrate the flow of steps in a process.

The following symbols are commonly used in flowcharts. These symbols are connected by lines with arrows to show the flow from one step to another.

Ovals are used to indicate both the start and end points in a series of steps.

A box is used to represent an individual step or activity in the process.

Yes A diamond shape shows a point in the process when a decision, such as yes or no, must be made. Lines extending from diamonds must be labeled with one of the possible answers.

A circle is used to indicate when a particular step is connected to another part or page of the flowchart. A letter is often put inside the circle to help clarify the continuation.

A triangle shows where a measurement is taken during the process.

Conditional statements reflected in a flowchart are used to create source code. Most programming languages use conditional statements such as if...then statements. For example, the following is a simple if...then statement about a coffee pot that directs the program to make coffee if the value or variable is equal to empty:

if coffee pot = empty

then make coffee



This simple flowchart shows how a conditional statement is used to help someone decide whether to go golfing.

Flowcharting can be beneficial to all types of people, not just programmers, because it helps clarify what actually happens or needs to happen in an event or process. You can also use flowcharts to train people (for example, to illustrate what to do in the event of a fire at your school). With a flowchart, it is easier for you to identify problem areas and opportunities for improvement.




Flowchart: Illustrating the Flow of LogicDirections: A flowchart can help you illustrate a decision-making process. Likewise, a computer program can be written based on a flowchart to illustrate the flow of logic in the program. Think about the flowchart shown in Student Resource 14.4, Reading: How Programming Languages Work, where the chart shows how a person might decide whether to play golf or stay home. Use it as a model to create your own simple flowchart. Follow your teacher’s instructions about how to draw the flowchart. Review the assessment criteria at the end of this assignment sheet before you begin work.

Choose from one of the following five flowchart topics, or ask your teacher for approval of a topic of your choice.

What movie should we see?

Where should we go on vacation?

What should we eat for dinner tonight?

Should I take an art class or a music class next semester?

Should I wear shorts or long pants to school tomorrow?

As you draw your chart, remember to use the formal flowcharting symbols you learned in the reading. Be sure that you include each of these on your chart:

Start

At least five steps or activities

Yes/no decisions

Stop

Refer to Student Resource 14.4, Reading: How Programming Languages Work, as you work on your chart.

Make sure your assignment meets or exceeds the following assessment criteria: The chart correctly shows the flow for one of the suggested topics.

The chart uses formal flowchart symbols correctly.

The chart has correct start and end points.

A yes/no decision is used correctly.

The chart includes a loop to show different outcomes for the yes/no question’s answers.

The chart is neat and uses proper spelling and grammar.




Programming Assignment: JavaScript ProgramStudent Name:_____________________________________________________ Date:_____________

Directions: Some people think that all computer code is complicated and hard to understand, but chances are they have never written a simple program. This hands-on exercise will teach you some basic HTML code and help you write your first computer program in the JavaScript language.

Before you begin, think back to what you already know about web pages. You know that web pages are displayed using a web browser (such as Internet Explorer, Firefox, Chrome, or Safari) and that they are written using a computer language called Hypertext Markup Language (HTML). You might also know that other information, in a language called JavaScript, can be added to create features such as a pop-up window, a clock, or an animated button.

Understanding HTMLAll web pages are written, at the most basic level, pretty much alike. The information a programmer wants to tell the computer is enclosed in something called a tag. A tag is simply a command letting the web browser know to begin doing something or to stop doing something. To begin writing a web page, you first let the computer know that it needs to begin reading HTML. The code looks like this:

<html>

<body>

Below the <body> tag, you write the code for what you want to put on your web page—things like headings, paragraphs, lists, pictures. After you code all of the content, you end your page with the closing tags to tell the computer the page is finished:

</body>

</html>

When you create a tag, use angle brackets (< > symbols) to surround the tag itself. To signal that a particular part is completed, you enclose the “end tag” in angle brackets and use a slash before the command: </ >.

Many HTML tags are quite easy to guess, once you have the hang of it. Some of the most common are as follows:

<strong>bold</strong> Makes a word bold

<em>italics</em> Makes a word appear in italics

<u>underline</u> Makes a word underlined

<font color=green>text</font> Makes text green

<ul><li>bulleted list</li></ul> Creates a bulleted list

<a href="URL goes here">Name of linked page</a>

Inserts a link


http://www.naf.org/


Writing JavaScriptDirections: In this exercise, you’ll practice writing JavaScript, one of the most commonly used scripting languages on the web. You’ll also use a few standard HTML tags, into which you will insert your JavaScript code. Follow the instructions to write these JavaScript programs. If you don’t get the expected output, ask your teacher or a fellow student for help.

1. Let’s get started with something simple: making the phrase “Hello, World!” appear on your computer screen. Using WordPad or another text editor, copy the following text into a new, blank document.

<html>

<body>

<script type="text/javascript">

document.write("Hello, World!");

</script>

</body>

</html>

Be careful when typing this text—remember that even one typo will cause a syntax error, which will prevent the code from running. When you are done, save the file as a text document and name it hello.html. Next, double-click the new HTML file. What happens?

As you have probably guessed, the text from <script> to </script> is the JavaScript telling the web page to display its message.

Troubleshooting

If your message doesn’t appear on the screen, check the following:

Did you create the document using a text editor like Notepad or WordPad? (You need to use a text editor rather than a program like Microsoft Word for writing code, because a text editor does not insert any formatting.)

Did you save your file with the file extension .html? You have to give the file a file name that ends in .html in order for your computer to know how to open it.

Have a partner double-check that you typed the text exactly as it appears above, with no syntax errors.

If you got an error message rather than a message display, it may be because of the way security policies are configured on your computer. In this case, check with your teacher about what to do next.

2. Now let’s try something a bit more advanced. Type the following text into a text editor document, as you did in the previous example.

<html>

<body>


document.write("<h1>This is a header</h1>");

</script>



</body>

</html>

Again, be careful when typing to avoid a syntax error. When you are done, save the file as header.html. Then, double-click the new HTML file. What happens this time?

3. Now try this final sample piece of code to create a button that makes a pop-up window appear. As before, open a document using a text editor, type the following code, and save it as button.html.

<html>

<head>


function disp_alert()

{

alert("I am an alert box!!");

}

</script>

</head>

<body>

<input type="button" onclick="disp_alert()" value="Click Me" />

</body>

</html>

The HTML commands (tags) and JavaScript scripting information work together to create these programs.

4. Now it’s your turn to use the information from the programs you’ve tried on this worksheet and write your own JavaScript program. Write a piece of JavaScript code to display your name and the name of your school. Use the space below to write a draft of what you will code before you code it on the computer. Remember to open and close the program using the HTML tags you’ve seen in this student resource.

When you enter your code on the computer, save it as an HTML file, run it, and print a screenshot of your program’s results. Submit the screenshot and this page with a draft of your source code for your teacher’s review.



5. Make a pop-up window to tell what your teacher’s name is. Remember to open and close the program using the HTML tags you’ve seen on this worksheet. When you have written your code, save it as an HTML file, run it, and print a screenshot of your program’s results. Submit the screenshot and this page with a draft of your source code for your teacher’s review.




Reading: The Software Development Process

Software Development TodayIn the early days of computing, software development was simply a single programmer writing code in order to solve a problem or computerize a process. However, today’s computer systems are so large and so complex that a team of people is commonly needed to build a successful software product.

A software development team can include project managers, systems analysts, software designers, programmers, testers, marketers, technical writers, and even software users like you. A set of agreed-upon principles, methods, and tools are used to coordinate the team’s efforts so that the software project meets its goals.

Typical Phases in the “Life” of a Software ProductTo help manage the software development process, the software development life cycle (SDLC) was created. The SDLC is an organized way to build a software system or product. Although some development teams break down the steps in the SDLC in slightly different ways, the following phases are typical:

1. Write the problem statement: This phase establishes a big-picture view of the intended project and determines its goals. This process may involve software users (called end users) who provide ideas for improving the project. This phase also includes conducting preliminary research to see whether the proposed solution is cost effective.

2. Write the requirements: This phase is for analyzing the needs of end users and translating project goals into specific, practical requirements.

3. Design the first version of the program: In this phase, developers describe in detail all the features and operations of the system or product to meet the needs defined in the planning phase. The design serves as a type of blueprint for the project and helps detect potential problems in the plan before programming is started. This phase often includes the creation of a prototype that shows how screens will look and how processes will flow.

4. Code/test/fix the first version: This phase involves the writing and debugging of code to create an alpha (first) version of the software.

5. Design the next version of the program: After adjustments are made to the alpha version, a beta (second) version is designed. End users often play a key role by helping to test the system or product in this phase.

6. Code/test/fix the next version: In this phase, the beta code is created, tested, and fixed.

7. Deploy/maintain/evaluate the first code “release” and plan for the next release: After final adjustments have been made to the beta version, what is sometimes called a “gold master” is put into production (manufactured) and released to the public (or a specific customer) for installation and actual use. Then planning begins for the next product release.

This process is iterative—in other words, after you complete step 7, you need to “circle back” and work through the steps again, starting with step 1. In a commercial programming organization, the process continues to iterate as long as the software product is supported in the marketplace.



When you illustrate an iterative process, you need to be sure you show the iteration graphically. For example, if you used flowcharting to illustrate the software development process, you might draw or print an arrow starting from step 7 and going back up to step 1.

Mistakes to Avoid The following are examples of mistakes that can cause a project to fail:

Not defining the problem statement or the project requirements clearly and accurately

Not getting everyone concerned with the project to agree on the problem statement or project requirements

Not adequately identifying or distributing resources among team members

Not properly tracking the progress of the project, in terms of cost and schedule

Not identifying or addressing potential threats to the success of the project—in other words, not gathering enough information and/or ignoring potential problems

Iterating only once through the process—for example, not gathering customer feedback on a software product already in the field and adjusting future product plans to customer requirements

Suggested Practices The following are some generally accepted tips to use when developing software:

Be very thorough in gathering product requirements, and document them in writing. Make sure that all those involved with the project agree on these requirements.

Break large tasks into smaller, manageable pieces, and identify deadlines for each.

To ensure accountability from all team members, make sure that deadlines are clear and that people are required to report regularly on their progress.

Include procedures throughout the project for monitoring and maintaining quality. This includes frequent testing. Peer review, a process used for checking work by one’s own equals or peers, is a good idea.

Keep control of your project, but not too rigidly—change is a part of life, and that includes software development.

After the project is completed, ask the team to reflect on the project to identify what worked well and what should have been done differently. This information can be helpful for future projects.

Open Source Software’s Influence on Software DevelopmentWhen the source code (programming instructions) for a software product is made available to users and other developers, we refer to that software as open source software. The open source movement started because some developers thought that software products could be made better if companies and programmers worked together. Those who distribute open source software expect and encourage others to examine the source code to find problems and to make changes to improve the product. The Linux operating system is an example of open source software.

The availability of open source software has influenced software development in another way. Companies who develop proprietary software (software whose source code is not publicly available) have to work a little harder to keep their share of the computer market, because people now have open source alternatives.




Poster: The Software Development Life CycleDirections: Think about what you know about the software development life cycle (SDLC). How can you depict it visually on a poster?

With your group, create a poster that details the seven phases of the SDLC in the most creative way you can imagine. Though you are free to keep the poster computer-related only, think of other multiphase processes that you might encounter in nature or your own life and experiences that could be thought of similarly to the SDLC. Base your poster on the information you’ve gathered from reading and from your experiences in class. Review the assessment criteria at the end of the assignment sheet before you begin work.

Your poster should include the following:

An illustration or description of each phase of the SDLC (write the problem statement, write the requirements, design the first version of the code, code/test/fix the first version, design the next version, code/test/fix the next version, deploy/maintain/evaluate the first product release and plan for the next release)

A label that identifies each phase

A sentence that explains what happens during each phase

To make best use of the time of all members of your group, have each member draw one of the phases and then neatly and attractively paste it onto the poster.

Each group member’s drawing should be accompanied by the purpose sentence he or she has written explaining the phase. Make sure that whatever you write would make sense to someone who knows nothing about computers or the SDLC.

Make sure your assignment meets or exceeds the following assessment criteria: The poster accurately describes the various phases of the SDLC.

The poster’s graphic elements clearly illustrate the seven phases of the SDLC and the iterative nature of the process.

The poster’s text communicates what makes each feature useful.

The material on the poster keeps its audience in mind, using an appropriate level of detail to highlight how the SDLC operates.

The poster is neat and uses proper spelling and grammar.


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