c++ for dummys.txt

Both the newest, hottest ight simulator and the simplest yet most powerful accounting programs

         
 
                    Part I 
    Introduction to C++ Programming 
    
 
    In this part . . . 
    Both the newest, hottest ight simulator and the 
    simplest yet most powerful accounting programs 
    use the same basic building blocks. In this part, you dis 
    cover the basic features you need to write your killer 
    application. 
    
 
                                         Chapter 1
 
  Writing Your First C++ Program 
  In This Chapter 
  Finding out about C++ 
  Installing Dev-CPP from the accompanying CD-ROM 
  Creating your first C++ program 
  Executing your program 
  Okay, so here we are: No one here but just you and me. Nothing left to do 
            but get started. Might as well lay out a few fundamental concepts. 
            A computer is an amazingly fast but incredibly stupid machine. A computer 
            can do anything you tell it (within reason), but it does exactly what it’s told — 
            nothing more and nothing less. 
            Perhaps unfortunately for us, computers don’t understand any reasonable 
            human language — they don’t speak English either. Okay, I know what you’re 
            going to say: “I’ve seen computers that could understand English.” What you 
            really saw was a computer executing a program that could meaningfully under 
            stand English. (I’m still a little unclear on this computer-understanding-language 
            concept, but then I don’t know that my son understands my advice, either, so 
            I’ll let it slide.) 
            Computers understand a language variously known as computer language or 
            machine language. It’s possible but extremely difficult for humans to speak 
            machine language. Therefore, computers and humans have agreed to sort of 
            meet in the middle, using intermediate languages such as C++. Humans can 
            speak C++ (sort of), and C++ is converted into machine language for the com 
            puter to understand. 
       
 
10   Part I: Introduction to C++ Programming 
  Grasping C++ Concepts
 
                In the early 1970s, a consortium of really clever people worked on a computer 
                system called Multix. The goal of Multix was to give all houses inexpensive 
                computer access to graphics, e-mail, stock data, pornography (just kidding), 
                whatever. Of course, this was a completely crazy idea at the time, and the 
                entire concept failed. 
                A small team of engineers working for Bell Labs decided to save some portion 
                of Multix in a very small, lightweight operating system that they dubbed Unix 
                (Un-ix, the single task version of Mult-ix, get it?). 
                Unfortunately for these engineers, they didn’t have one large machine but a 
                number of smaller machines, each from a different manufacturer. The standard 
                development tricks of the day were all machine-dependent — they would have 
                to rewrite the same program for each of the available machines. Instead, these 
                engineers invented a small, powerful language named C. 
                C caught on like wildfire. Eventually, however, new programming techniques 
                (most notably object-oriented programming) left the C programming language 
                behind. Not to be outdone, the engineering community added equivalent new 
                features to the C language. The result was called C++. 
                The C++ language consists of two basic elements: 
                      Semantics: This is a vocabulary of commands that humans can under 
                      stand and that can be converted into machine language, fairly easily. 
                      and 
                      Syntax: This is a language structure (or grammar) that allows humans to 
                      combine these C++ commands into a program that actually does some 
                      thing (well, maybe does something). 
                Think of the semantics as the building blocks of your C++ program and the 
                syntax as the correct way to put them together. 
                What’s a program?
 
                A C++ program is a text file containing a sequence of C++ commands put 
                together according to the laws of C++ grammar. This text file is known as the 
                source file (probably because it’s the source of all frustration). A C++ source 
                file carries the extension .CPP just as a Microsoft Word file ends in .DOC or 
                an MS-DOS (remember that?) batch file ends in .BAT. The concept extension 
                .CPP is just a convention. 
           
 
                                    Chapter 1: Writing Your First C++ Program         11 
  The point of programming in C++ is to write a sequence of commands that can 
  be converted into a machine-language program that actually does what we want 
  done. The resulting machine-executable files carry the extension .EXE. The act 
  of creating an executable program from a C++ program is called compiling or 
  building (the subtle difference between the two is described in Chapter 22). 
  That sounds easy enough — so what’s the big deal? Keep going. 
  How do I program? 
  To write a program, you need two specialized computer programs. One (an 
  editor) is what you use to write your code as you build your .CPP source file. 
  The other (a compiler) converts your source file into a machine-executable 
  .EXE file that carries out your real-world commands (open spreadsheet, make 
  rude noise, deflect incoming asteroid, whatever). 
  Nowadays, tool developers generally combine compiler and editor into a single 
  package — a development environment. After you finish entering the commands 
  that make up your program, you need only click a button to create the exe 
  cutable file. 
  The most popular of all C++ environments is a Microsoft product, Visual 
  C++.NET (pronounced “Visual-C-plus-plus-DOT-net”). All programs in this 
  book compile and execute with Visual C++.NET; however, many of you may 
  not already own Visual C++.NET — and at $250 bucks a pop, street price, this 
  may be a problem. 
  Fortunately, there are public-domain C++ environments. We use one of them 
  in this book — the Dev-CPP environment. A recent version of Dev-CPP envi 
  ronment is included on CD-ROM enclosed at the back of this book (or you can 
  download the absolutely most recent version off the Web at www.bloodshed. 
  net). 
  You can download quite a range of public-domain programs from the Internet. 
  Some of these programs, however, are not free — you’re encouraged — or 
  required — to pay some (usually small) fee. You don’t have to pay to use Dev- 
  C++, but you can contribute to the cause if you like. See the Web site for details. 
  I have tested the programs in this book with Dev-C++ version 4.9.8.0; they 
  should work with other versions as well. You can check out my Web site at 
  www.stephendavis.com for a list of any problems that may arise with future 
  versions of Dev-C++ or Windows. 
  Dev-C++ is not some bug-ridden, limited edition C++ compiler from some fly- 
  by-night group of developers. Dev-C++ is a full-fledged C++ environment. Dev- 
  C++ supports the entire C++ language and executes all the programs in this 
  book (and any other C++ book) just fine, thank you. 
    
 
12   Part I: Introduction to C++ Programming 
                Dev-C++ does generate Windows-compatible 32-bit programs, but it does not 
                easily support creating programs that have the classic Windows look. If you 
                want to do that, you’ll have to break open the wallet and go for a commercial 
                package like Visual Studio.NET. Having said that, I strongly recommend that 
                you work through the examples in this book first to learn C++ before you tackle 
                Windows development. They are two separate things and (for the sake of 
                sanity) should remain so in your mind. 
                Follow the steps in the next section to install Dev-C++ and build your first C++ 
                program. This program’s task is to convert a temperature value entered by the 
                user from degrees Celsius to degrees Fahrenheit. 
                The programs in this book are compatible with Visual C++.NET and the C++ 
                section of Visual Studio.NET (which are essentially the same thing). Use the 
                documentation in the Visual C++ .NET for instructions on installing C++. True, 
                the error messages generated by Visual C++.NET are different (and often just 
                as difficult to decipher), but the territory will seem mysteriously familiar. Even 
                though you’re using a different songbook, you shouldn’t have much trouble 
                following the tune. 
  Installing Dev-C++
 
                The CD-ROM that accompanies this book includes the most recent version of 
                the Dev-C++ environment at the time of this writing. 
                The Dev-C++ environment comes in an easy-to-install, compressed executable 
                file. This executable file is contained in the DevCPP directory on the accom 
                panying CD-ROM. Here’s the rundown on installing the environment: 
                   1. Navigate to and double-click the file devcpp4980.exe, or (in Windows) 
                      click StartRun. 
                           Double-clicking the file installs the environment automatically. (Note 
                            that 4.9.8.0, the version number, will be different on any newer ver 
                            sion of Dev-C++ you downloaded off the Web.) 
                           If you clicked StartRun, type x:\devcpp\devcpp4980 in the Run 
                            window that appears, where x is the letter designation for your 
                            CD-ROM drive (normally D but perhaps E — if one doesn’t work, 
                            try the other). 
                            Dev-C++ begins with a warning (shown in Figure 1-1) that you’d better 
                            uninstall any older version of Dev-C++ you may have hanging around, 
                            and then reboot and start over. (Starting an installation with a threat 
                            is an inauspicious way to begin a relationship, but everything gets 
                            better from here.) 
           
 
                                              Chapter 1: Writing Your First C++ Program        13 
Figure 1-1: 
  You must 
  uninstall 
    earlier 
versions of 
  Dev-C++ 
before you 
 begin the 
installation 
  process. 
             2. If you don’t have to uninstall an old version of Dev-C++, skip to Step 4; 
                if you do have to uninstall, abort the current installation process by 
                closing the Run window. 
                Don’t get upset if you’ve never even heard of Dev-C++ and you still get the 
                warning message. It’s just a reminder. 
             3. Okay, if you’re on this step, you’re uninstalling: Open the Dev-CPP 
                folder and double-click the Uninstall.exe file there. 
                The uninstall program does its thing, preparing the way for the new instal 
                lation; the End User Legal Agreement (commonly known as the EULA) 
                appears. 
             4. Read the EULA and then click OK if you can live with its provisions. 
                Nope, the package really won’t install itself if you don’t accept. Assuming 
                you do click OK, Dev-C++ opens the window shown in Figure 1-2 and offers 
                you some installation options. The defaults are innocuous, with two 
                exceptions: 
                     You must leave the Mingw compiler system. . . option enabled. 
                     The Associate C and C++ Files to Dev-C++ option means that double- 
                      clicking a .CPP file automatically opens Dev-C++ rather than some 
                      other program (such as Visual C++ .NET, for example). It is possible, 
                      but difficult, to undo this association. 
                Don’t check this option if you also have Visual Studio.NET installed. Dev- 
                C++ and Visual Studio.NET coexist peacefully on the same machine, but 
                what Visual Studio has done, let no man cast assunder. You can still open 
                your .CPP files with Dev-C++ by right-clicking on the file and selecting Open 
                With. Personally, I prefer to use this option, even with Visual Studio.NET 
                installed. It doesn’t cause any problems, and Dev-C++ starts a lot faster 
                than Visual Studio. 
        
 
14   Part I: Introduction to C++ Programming 
      Figure 1-2: