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C++ Programming

This course teaches you the powerful, fast and popular C++ programming language from scratch, assuming only basic computer knowledge. If you want to develop apps that squeeze the most power from your computer -- high-end desktop games or complex artificial intelligence programs, for instance -- or if you want to use a language that let's you get close to your machine and access all of your computer's hardware, C++ is the language for you. While C++ is quite challenging, in this course we'll learn the basics step by step; towards the end of the course you'll learn how to create a beautiful "particle fire" program, including a smattering of the basic principles of game development.

The C++ programming language has a history going back to 1979, when Bjarne Stroustrup was doing work for his Ph.D. thesis. One of the languages Stroustrup had the opportunity to work with was a language called Simula, which as the name implies is a language primarily designed for simulations. The Simula 67 language - which was the variant that Stroustrup worked with - is regarded as the first language to support the object-oriented programming paradigm. Stroustrup found that this paradigm was very useful for software development, however the Simula language was far too slow for practical use.

Shortly thereafter, he began work on "C with Classes", which as the name implies was meant to be a superset of the C language. His goal was to add object-oriented programming into the C language, which was and still is a language well-respected for its portability without sacrificing speed or low-level functionality. His language included classes, basic inheritance, inlining, default function arguments, and strong type checking in addition to all the features of the C language.

The first C with Classes compiler was called Cfront, which was derived from a C compiler called CPre. It was a program designed to translate C with Classes code to ordinary C. A rather interesting point worth noting is that Cfront was written mostly in C with Classes, making it a self-hosting compiler (a compiler that can compile itself). Cfront would later be abandoned in 1993 after it became difficult to integrate new features into it, namely C++ exceptions. Nonetheless, Cfront made a huge impact on the implementations of future compilers and on the Unix operating system.

In 1983, the name of the language was changed from C with Classes to C++. The ++ operator in the C language is an operator for incrementing a variable, which gives some insight into how Stroustrup regarded the language. Many new features were added around this time, the most notable of which are virtual functions, function overloading, references with the & symbol, the const keyword, and single-line comments using two forward slashes (which is a feature taken from the language BCPL).

In 1985, Stroustrup's reference to the language entitled The C++ Programming Language was published. That same year, C++ was implemented as a commercial product. The language was not officially standardized yet, making the book a very important reference. The language was updated again in 1989 to include protected and static members, as well as inheritance from several classes.

In 1990, The Annotated C++ Reference Manual was released. The same year, Borland's Turbo C++ compiler would be released as a commercial product. Turbo C++ added a plethora of additional libraries which would have a considerable impact on C++'s development. Although Turbo C++'s last stable release was in 2006, the compiler is still widely used.

In 1998, the C++ standards committee published the first international standard for C++ ISO/IEC 14882:1998, which would be informally known as C++98. The Annotated C++ Reference Manual was said to be a large influence in the development of the standard. The Standard Template Library, which began its conceptual development in 1979, was also included. In 2003, the committee responded to multiple problems that were reported with their 1998 standard, and revised it accordingly. The changed language was dubbed C++03.

In 2005, the C++ standards committee released a technical report (dubbed TR1) detailing various features they were planning to add to the latest C++ standard. The new standard was informally dubbed C++0x as it was expected to be released sometime before the end of the first decade. Ironically, however, the new standard would not be released until mid-2011. Several technical reports were released up until then, and some compilers began adding experimental support for the new features.

In mid-2011, the new C++ standard (dubbed C++11) was finished. The Boost library project made a considerable impact on the new standard, and some of the new modules were derived directly from the corresponding Boost libraries. Some of the new features included regular expression support (details on regular expressions may be found here), a comprehensive randomization library, a new C++ time library, atomics support, a standard threading library (which up until 2011 both C and C++ were lacking), a new for loop syntax providing functionality similar to foreach loops in certain other languages, the auto keyword, new container classes, better support for unions and array-initialization lists, and variadic templates.

Computers understand only one language and that language consists of sets of instructions made of ones and zeros. This computer language is appropriately called machine language.

A single instruction to a computer could look like this:  00000    10011110

A particular computer's machine language program that allows a user to input two numbers, adds the two numbers together, and displays the total could include these machine code instructions:

00000       10011110
00001       11110100
00010       10011110
00011       11010100
00100       10111111
00101       00000000

As you can imagine, programming a computer directly in machine language using only ones and zeros is very tedious and error prone. To make programming easier, high level languages have been developed. High level programs also make it easier for programmers to inspect and understand each other's programs easier.

This is a portion of code written in C++ that accomplishes the exact same purpose:

int a, b, sum;
cin << a;
cin << b;
sum = a + b;
cout << sum << endl;

Even if you cannot really understand the code above, you should be able to appreciate how much easier it will be to program in the C++ language as opposed to machine language.

Because a computer can only understand machine language and humans wish to write in high level languages high level languages have to be re-written (translated) into machine language at some point. This is done by special programs called compilers, interpreters, or assemblers that are built into the various programming applications.

C++ is designed to be a compiled language, meaning that it is generally translated into machine language that can be understood directly by the system, making the generated program highly efficient. For that, a set of tools are needed, known as the development toolchain, whose core are a compiler and its linker.

The best way to learn a programming language is by writing programs. Typically, the first program beginners write is a program called "Hello World", which simply prints "Hello World" to your computer screen. Although it is very simple, it contains all the fundamental components C++ programs have:

// my first program in C++
#include < iostream >
int main()
{
std::cout << "Hello World!";
}

The output will be : Hello World!

The left panel above shows the C++ code for this program. The right panel shows the result when the program is executed by a computer. The grey numbers to the left of the panels are line numbers to make discussing programs and researching errors easier. They are not part of the program.

Let's examine this program line by line:

  • Line 1: // my first program in C++
    Two slash signs indicate that the rest of the line is a comment inserted by the programmer but which has no effect on the behavior of the program. Programmers use them to include short explanations or observations concerning the code or program. In this case, it is a brief introductory description of the program.
  • Line 2: #include < iostream >
    Lines beginning with a hash sign (#) are directives read and interpreted by what is known as the preprocessor. They are special lines interpreted before the compilation of the program itself begins. In this case, the directive #include , instructs the preprocessor to include a section of standard C++ code, known as header iostream, that allows to perform standard input and output operations, such as writing the output of this program (Hello World) to the screen.
  • Line 3: A blank line.
    Blank lines have no effect on a program. They simply improve readability of the code.
  • Line 4: int main ()
    This line initiates the declaration of a function. Essentially, a function is a group of code statements which are given a name: in this case, this gives the name "main" to the group of code statements that follow. Functions will be discussed in detail in a later chapter, but essentially, their definition is introduced with a succession of a type (int), a name (main) and a pair of parentheses (()), optionally including parameters.
    The function named main is a special function in all C++ programs; it is the function called when the program is run. The execution of all C++ programs begins with the main function, regardless of where the function is actually located within the code.
  • Lines 5 and 7: { and }
    The open brace ({) at line 5 indicates the beginning of main's function definition, and the closing brace (}) at line 7, indicates its end. Everything between these braces is the function's body that defines what happens when main is called. All functions use braces to indicate the beginning and end of their definitions.
  • Line 6: std::cout << "Hello World!";
    This line is a C++ statement. A statement is an expression that can actually produce some effect. It is the meat of a program, specifying its actual behavior. Statements are executed in the same order that they appear within a function's body.
    This statement has three parts: First, std::cout, which identifies the standard character output device (usually, this is the computer screen). Second, the insertion operator (< <), which indicates that what follows is inserted into std::cout. Finally, a sentence within quotes ("Hello world!"), is the content inserted into the standard output.
    Notice that the statement ends with a semicolon (;). This character marks the end of the statement, just as the period ends a sentence in English. All C++ statements must end with a semicolon character. One of the most common syntax errors in C++ is forgetting to end a statement with a semicolon.

The smallest unit of memory is a binary digit (bit), which can hold a value of 0 or 1. You can think of a bit as being like a traditional light switch -- either the light is off (0), or it is on (1). There is no in-between. If you were to look at a random segment of memory, all you would see is …011010100101010… or some combination thereof. Memory is organized into sequential units called addresses. Similar to how a street address can be used to find a given house on a street, the memory address allows us to find and access the contents of memory at a particular location. Perhaps surprisingly, in modern computers, each bit does not get its own address. The smallest addressable unit of memory is a group of 8 bits known as a byte.

Defining a variable :
In the “basic C++? section, you already learned how to define an integer variable:
int nVarName; // int is the type, nVarName is the name of the variable

  • First, variables that are defined only when needed are given context by the statements around them. If x were defined at the top of the function, we would have no idea what it was used for until we scanned the function and found where it was used. Defining x amongst a bunch of input/output statements helps make it obvious that this variable is being used for input and/or output.
  • Second, defining a variable only where it is needed tells us that this variable does not affect anything above it, making our program easier to understand and requiring less scrolling.
  • Finally, it reduces the likelihood of inadvertently leaving a variable uninitialized, because we can define and then immediately initialize it with the value we want it to have.

In order to properly evaluate an expression such as 4 + 2 * 3, we must understand both what the operators do, and the correct order to apply them. The order in which operators are evaluated in a compound expression is called operator precedence. Using normal mathematical precedence rules (which state that multiplication is resolved before addition), we know that the above expression should evaluate as 4 + (2 * 3) to produce the value 10.

In C++, all operators are assigned a level of precedence. Those with the highest precedence are evaluated first. You can see in the table below that multiplication and division (precedence level 5) have a higher precedence than addition and subtraction (precedence level 6). The compiler uses these levels to determine how to evaluate expressions it encounters.

Thus, 4 + 2 * 3 evaluates as 4 + (2 * 3) because multiplication has a higher level of precedence than addition.

If two operators with the same precedence level are adjacent to each other in an expression, the associativity rules tell the compiler whether to evaluate the operators from left to right or from right to left. For example, in the expression 3 * 4 / 2, the multiplication and division operators are both precedence level 5. Level 5 has an associativity of left to right, so the expression is resolved from left to right: (3 * 4) / 2 = 6.

Each of the variables in an array is called an element. Elements do not have their own unique names. Instead, to access individual elements of an array, we use the array name, along with the subscript operator ([]), and a parameter called a subscript (or index) that tells the compiler which element we want. This process is called subscripting or indexing the array.

In C++, operators are implemented as functions. By using function overloading on the operator functions, you can define your own versions of the operators that work with different data types (including classes that you’ve written). Using function overloading to overload operators is called operator overloading.

Object composition is perfect for building new objects that have a “has-a? relationship with their parts. However, object composition is just one of the two major ways that C++ lets you construct complex classes. The second way is through inheritance, which models an is-a relationship between two objects.

Unlike object composition, which involves creating new objects by combining and connecting other objects, inheritance involves creating new objects by directly acquiring the attributes and behaviors of other objects and then extending or specializing them. Like object composition, inheritance is everywhere in real life. When you were conceived, you inherited your parents genes, and acquired physical attributes from both of them -- but then you added your own personality on top. Technological products (computers, cell phones, etc…) inherit features from their predecessors (often used for backwards compatibility). For example, the Intel Pentium processor inherited many of the features defined by the Intel 486 processor, which itself inherited features from earlier processors. C++ inherited many features from C, the language upon which it is based, and C inherited many of its features from the programming languages that came before it.

Consider apples and bananas. Although apples and bananas are different fruits, both have in common that they are fruits. And because apples and bananas are fruits, simple logic tells us that anything that is true of fruits is also true of apples and bananas. For example, all fruits have a name, a color, and a size. Therefore, apples and bananas also have a name, a color, and a size. We can say that apples and bananas inherit (acquire) these all of the properties of fruit because they are fruit. Apples and bananas then define these inherited properties accordingly (apples are red or green, bananas are yellow, apples are about the size of a baseball, bananas are about the size of a zucchini).

The Standard Template Library is a collection of classes that provide templated containers, algorithms, and iterators. If you need a common class or algorithm, odds are the STL has it. The upside is that you can take advantage of these classes without having to write and debug the classes yourself, and the STL does a good job providing reasonably efficient versions of these classes. The downside is that the STL is complex, and can be a little intimidating since everything is templated.

Fortunately, you can bite off the STL in tiny pieces, using only what you need from it, and ignore the rest until you’re ready to tackle it.

Input and output functionality is not defined as part of the core C++ language, but rather is provided through the C++ standard library (and thus resides in the std namespace). In previous lessons, you included the iostream library header and made use of the cin and cout objects to do simple I/O. In this lesson, we’ll take a look at the iostream library in more detail.

The iostream library

When you include the iostream header, you gain access to a whole hierarchy of classes responsible for providing I/O functionality (including one class that is actually named iostream).

To recap the process needed to use a library:

Once per library:

  • Acquire the library. Download it from the website or via a package manager.
  • Install the library. Unzip it to a directory or install it via a package manager.
  • Tell the compiler where to look for the header file(s) for the library.
  • Tell the linker where to look for the library file(s) for the library.

Once per project:

  • Tell the linker which static or import library files to link.
  • #include the library’s header file(s) in your program.
  • Make sure the program know where to find any dynamic libraries being used.

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