C++ Projects

C++ Instructions

C++ works by giving (separate) instructions to the computer. These instructions can be treated as assignments. On this site, such an assignment will be called a function. The primary function used in C++ is called main. To distinguish a function from the other types of things you will be using in your programs, a function's name is followed by an opening and a closing parentheses. For example, the main function will always be written at least as main(). When we perform a better study of functions, we will learn more about functions, their parentheses, and other related issues.

When a program is written and you ask the computer to "execute" it, the first thing to look for is the main() function. This means that every C++ program should have the main() function. Because a function is an assignment, in order to perform its job, a function has a body; this is where the behavior (assignment) of the function would be "described". The body of a function starts with an opening curly bracket "{" and closes with a closing curly bracket "}". Everything in between belongs to, or is part of, the function. Therefore, the main() function can be written as:

main() {}

As we learned that we should (must) always include the libraries that we would need, our program now would include main(). Whenever you create a program, it is important to isolate any inclusion of a library on its own line. Here is an example:

#include
using namespace std;
main(){}

C++ is the computer language we are going to study to write programs. C++ is a very universal language, it can be used to write programs for Linux, MS Windows, Macintosh, BeOS, Unix, etc. C++ is very powerful and can be used to create other compilers or languages, it can also be used to write an operating system. This means that you can use C++ to create/write your own computer language. You can also use C++ to create/write your own compiler; this means that, using C++, you can create your own implementation of C++, Pascal, Basic, Perl, or any other existing or non-existing language.

There are many products you can use to create a program in C++. Before a program is made available, it is called a project because you are working on it. Although in the beginning you will usually be working alone, most programs involve a lot of people. That is why during the development of a program or software product, it is called a project. Each one of the available environments provides its own technique(s) of creating a C++ program or working on a C++ project. Therefore, the person who, or the company that, made the environment available to you must tell you how to use that environment (it is neither your responsibility, nor the C++ Standard’s job to tell you how to create a program or how to start a project). I will try to cover those that I know.

The programs we will be creating on this site are called console applications. They can also be called Bash programs (especially on Unix/Linux). The technique you follow to create a project depends on the environment you are using.

Executing a Program

To see what your program does, you need to realize that the lines we have typed are English language instructions asking C++ to perform the main() function. Unfortunately, the computer doesn't understand what all of this means (to a certain extent). The computer has its own language known as the machine language. So, we need to translate it in a language the computer can understand. A program was created to that effect and supplied to you with C++. This is what we call a compiler.

In the past, a program used to be created from various parts all over the computer, some of the techniques are still used to "debug" a program to isolate problems or "bugs". Since this is a small program, we will just ask the computer to "execute" it and see the result. Throughout this site, the words (or verbs) "execute" and "run" will be used interchangeably to mean the same thing.

The C++ language doesn't define how to create a project. When you buy or acquire a c++ compiler, its documentation should tell you how to create and execute a project. We describe here how how to create a project in most familiar environments. If you have an environment or compiler that is not in our list, consult its documentation to know how to use it.

One of our most valuable goals in writing a site is to avoid including in a program an issue that has not previously been addressed or explained. This site is written as a (general) reference towards the C++ language. To learn C++, you need a C++ compiler, and we describe how to create a C++ project with some of the most commonly used compilers or programming environments. As it happens, and as you may have noticed, different companies (and different individuals for that matter) choose to implement a language as they see fit.

Depending on the programming environment you are using, even depending on how you create your program (for example KDevelop, Borland C++ Builder, and Microsoft Visual C++ all provide more than one way to create or start a console application), sometimes you have a starting empty file or a file with a few lines. Whatever is in the file, you do not need to delete it. For example, KDevelop displays a commented message in the file. You should not delete that text and it will never interfere with your program. Borland C++ Builder opens a file with a couple of "#pragma" lines. You will never have any reason to delete those lines, although you can, without any risk; but since they do not affect your program, why waste your time deleting them?

Depending on the programming environment you are using and how you create your program, the first file may display a line as #include or another #include line. The file may also have a main() function already included. Here is how we will deal with this issue:

• If the file displays a line with #include Something, leave it as is. It will not negatively affect your program. Such a file has been tested
• If the file displays a line with #include , leave it like that and continue with our other instructions
• If the file is empty or it does not include a line with #include at all, then you will just follow our instructions and type them as given
• If the file already includes the main() function, with a line like int main(Something), use that main() function for the exercises in this book. Unless stated otherwise, that function is ready for you and don't modify the Something part between the parentheses.

From now on, you will sometimes be asked to create a project. Follow the instructions of your compiler as we have seen above.