Introduction to C++
Instead of going straight to the coding part, it's better to make some context. Let's start with a bit of history.
Brief history
C++ is a programming language made by Bjarne Stroustrup at Bell Labs, starting in 1979.
It was not created from the ground up, but it was rather an evolution of the already existing C language (created by Dennis Ritchie), with the main goal of adding the new OOP (Object Oriented Programming) programming paradigm support, which was not present in C.
C++ was standardized in 1998, and since then several updates have been made. C++11 in particular added a huge number of new capabilities, and new upgrades to the language are expected every three or so years.
Originally, the language was called "C with classes", but then C++ became the final name
because ++ is an operator that increments the value of a variable, and using the "+"
sign is a common naming convention among software developers to indicate an enhanced
computer program.
If you are curious, there's a much more in-depth explanation here, done by GeeksforGeeks.
Characteristics of C++
C++ is a hybrid language, so it contains not only object-oriented language but also the functionality of the C programming language, so traditional procedural programming. This means that you have all the features that are available in C, like:
- universally usable modular programs
- efficient, close to the machine programming
- portable programs for various platforms.
Existing C source code can be used in C++ programs.
Various language elements were added to C++ other than the OOP programming paradigm, such as references, templates, exception handling and many more things that are important for an efficient program implementation.
Don't worry, though! You don't have to already know all those concepts to start coding.
Why use it
Both C and C++ are very famous and largely used for a wide range of software types and platforms.
The advantages and features of the C++ language are many, but one of its strengths is that the compilation and execution time is really fast. That's probably the main reason why it's often chosen over other languages, but it's not the only one.
Another key aspect of C++ is its high-level nature, making it easier to learn, read, understand, and, most importantly, to work with.
In addition to being a high-performance language, it also gives the programmer precise control over memory and other resources of the computer, making it a bit harder to learn but also more powerful and capable of doing more things.
There's a nice overview of the advantages of learning C++ on this website by Programiz.
Where it's used
- Video games (especially for graphic engines and game development, e.g. in Unreal Engine)
- Operating systems (also in C language)
- Real-time systems (e.g. for transportation, manufacturing, etc…)
- High-performance financial applications (e.g. high-frequency trading)
- Graphical applications and simulations
- Embedded software (also in C language)
- Audio and video processing
- Artificial intelligence, machine learning and neural networks
- Scientific research
- Web browsers (like Chrome and Firefox)
- GUI Based Applications
- Databases
- Compilers of various high-level programming languages, like C# and Java (also in C language)
- Productivity software (MS Office, Photoshop, Maya/3ds Max, SolidWorks, Inventor, AutoCAD…)
Basic information
Structure of a program
The structure of a program in C++ can vary, but in its basic form it looks like this:
#include <...>
using namespace ...;
int main()
{
...
return 0;
}
We will see what those words mean and what to put instead of the generic three dots
..., but for what matters in this section, it's just important to remember that each
program that you write contains a main() function, and here you will write
the instructions needed for the program to work properly.
Every single program must have that special function, called in that way (all lowercase letters). When the program is run, the instructions or statements inside of main are executed in sequential order.
We'll cover what a function is in a future chapter, but for now, just know that it is a
collection of instructions that can be reused and they have a name that identifies them
followed by two parentheses at the end like this: function() and eventually some
"things" inside (...), called parameters.
Comments
A comment in computer programming is a programmer-readable explanation or annotation in the source code of a computer program1. This text is inserted in the code by the programmer, and it's not processed by the compiler (or interpreter), meaning that it's completely ignored in the execution phase. Comments' purpose is just to make the source code easier for humans to understand.
A comment in C++ can be added in two ways, like below:
// this is a single-line comment
Not a comment
/*
This is a
multi-line
comment that
spans multiple
lines
*/
Not a comment, too
Single line comments are considered comments only if the text is typed in the same line
of the two slashes //. In other words, // indicates that everything following it
until the end of the line is a comment.
A multi-line comment, instead, is considered a comment if the text is typed between
/* and */.
Do not use multi-line comments inside other multi-line comments.
Indentation
Indentation is a term that expresses the action of putting whitespace for formatting purposes.
It means adding some empty space among the code in the right way so that it becomes more readable.
Some languages like Python use indentation as an important part of their syntax, and it influences how the code is interpreted by the interpreter.
This does not happen in C and C++, because the compiler ignores whitespace. For this reason, we say that they are whitespace-independent languages. Instead, we use braces to tell the compiler that a piece of code belongs (it's inside) a block of other code or not.
That means that indentation would be optional, but it's important anyway for keeping a good level of readability.
Usually, if you use an IDE with a text editor, when you press ENTER/RETURN ⏎ on the keyboard it automatically adds one tab-sized whitespace. In the other cases, you can add it by pressing the TAB ⇆ key. It's also fine using four (or sometimes three or two) spaces instead, but I wouldn't recommend that.
Indentation is used like this:
int main() {
...
...
> > codeBlock() {
...
...
> > > > nestedCodeblock() {
...
...
> > > > }
...
...
> > }
...
...
}
The > signs are there only to indicate more clearly the whitespace added for indentation,
but they are not actually used in real code. As you can see, the indentation creates a
tree-like structure that makes code more beautiful and less difficult to read.
The type of indentation styling used above (and the one I personally prefer) is called K&R style, or "one true brace style". It's one of the most common together with the Allman style and you can freely choose the one you prefer. To read the full list of indentation styles, visit the Wikipedia page.
Development phases
A computer program is realized by passing through different phases. I already discussed the phases of the creation of a program in the previous section, but here we are talking more specifically about the programming phase. Let's see how it works.
What's an IDE
To run the programs that we'll make, we need a place to execute the code. The IDEs out there will help us.
IDE is an acronym that stands for Integrated Development Environment, and it's an environment, place, or piece of software that helps the programmer in the development and debugging phases of a program.
It provides the developer with some facilities and tools, like a source code editor, build automation tools and a debugger.
We are mainly interested in the debugger, which is a computer program that basically runs the code and shows us the output with the command prompt, if requested.
There are many IDEs to choose from, both open source and paid. Personally, I use Dev-C++, which compiles also C language. You can download it here (it's open source).
This IDE has long since been abandoned and it's not used in professional fields, but Orwell (an independent programmer) has taken it up and updated it. At the moment of writing, it supports the C++11 standard, and although the modern standard is C++14, we don't care about that for our learning purposes.
If you prefer to use another IDE, that's perfectly fine, but be sure that it has a compiler integrated. Also, you can use online compilers too, but some libraries will not be present, so programs that will use them won't work.
Compilation (translation)
After having saved the source code into a source file (or several source files that are
edited and translated separately in larger projects when doing modular programming) with
the .cpp extension, that source file is put through a compiler for translation.
The compiler checks the syntactic correctness of the code in accordance with the rules
established by the programming language used. If errors are present, the compiler lists
them.
If everything works as planned, an object file made up of machine code is created. The object file is also referred to as a module and can be directly executed by the processor (unlike source code).
Linking
Finally, in case the construction of the final program requires the union of one or more
modules and/or needs to integrate the code contained in the libraries (included at the top),
the linker combines the object file with other modules to form an executable file .exe.
These further modules contain functions from standard libraries or parts of the program
that have been compiled previously.
Debugging
Debugging is made by the debugger, which is a program that reads step by step every single line of code to check if there are any errors that are causing malfunctions in the program itself.