Basic C++ Commands and What They Do
Basic C++ Commands and What They Do
These processes are based off the basic "Hello World" program.
// creates a comment line. All lines beginning with "//" are considered comment lines, and do not effect the program in any way. A programmer can use these to give brief explanations of a code within the code itself.
Lines beginning with a number (hash) sign "#" are directives for the preprocessor. They are not regular code lines with expressions but indications for the compiler's preprocessor. Basically, they tell the program to include certain library files. This specific file (iostream) includes the declarations of the basic standard input-output library in C++, and it is included because its functionality is going to be used later in the program.
All the elements of the standard C++ library are declared within what is called a namespace, the namespace with the name std. So in order to access its functionality we declare with this expression that we will be using these entities. This line is very frequent in C++ programs that use the standard library, and in fact it will be included in most of the source codes included in these tutorials.
This line corresponds to the beginning of the definition of the main function. The main function is the point by where all C++ programs start their execution, independently of its location within the source code. It does not matter whether there are other functions with other names defined before or after it - the instructions contained within this function's definition will always be the first ones to be executed in any C++ program. For that same reason, it is essential that all C++ programs have a main function.
The word main is followed in the code by a pair of parentheses (()). That is because it is a function declaration: In C++, what differentiates a function declaration from other types of expressions are these parentheses that follow its name. Optionally, these parentheses may enclose a list of parameters within them.
Right after these parentheses we can find the body of the main function enclosed in braces ({}). What is contained within these braces is what the function does when it is executed.
This line is a C++ statement. A statement is a simple or compound expression that can actually produce some effect. In fact, this statement performs the only action that generates a visible effect in our first program.
cout is the name of the standard output stream in C++, and the meaning of the entire statement is to insert a sequence of characters (in this case the Hello World sequence of characters) into the standard output stream (cout, which usually corresponds to the screen).
cout is declared in the iostream standard file within the std namespace, so that's why we needed to include that specific file and to declare that we were going to use this specific namespace earlier in our code.
Notice that the statement ends with a semicolon character (
. This character is used to mark the end of the statement and in fact it must be included at the end of all expression statements in all C++ programs (one of the most common syntax errors is indeed to forget to include some semicolon after a statement).
The return statement causes the main function to finish. return may be followed by a return code (in our example is followed by the return code with a value of zero). A return code of 0 for the main function is generally interpreted as the program worked as expected without any errors during its execution. This is the most usual way to end a C++ console program.
And your finished code should be:
Yes I did copy and paste some of this.
If you want the program to stay open until you hit enter, this is the code:
Just change
to
Code:
//
Code:
#include < iostream>
Code:
using namespace std;
Code:
int main ()
The word main is followed in the code by a pair of parentheses (()). That is because it is a function declaration: In C++, what differentiates a function declaration from other types of expressions are these parentheses that follow its name. Optionally, these parentheses may enclose a list of parameters within them.
Right after these parentheses we can find the body of the main function enclosed in braces ({}). What is contained within these braces is what the function does when it is executed.
Code:
cout << "Hello World!";
cout is the name of the standard output stream in C++, and the meaning of the entire statement is to insert a sequence of characters (in this case the Hello World sequence of characters) into the standard output stream (cout, which usually corresponds to the screen).
cout is declared in the iostream standard file within the std namespace, so that's why we needed to include that specific file and to declare that we were going to use this specific namespace earlier in our code.
Notice that the statement ends with a semicolon character (
. This character is used to mark the end of the statement and in fact it must be included at the end of all expression statements in all C++ programs (one of the most common syntax errors is indeed to forget to include some semicolon after a statement).Code:
return 0;
And your finished code should be:
Code:
//Tony's C++ Program
#include <iostream>
using namespace std;
int main()
{
cout << "Hello MPGH";
cout << "Don't hate on this, it helps.";
return 0;
}
If you want the program to stay open until you hit enter, this is the code:
Code:
//Tony's C++ Program
#include <iostream>
using namespace std;
int main()
{
cout << "Hello MPGH";
cout << "Don't hate on this, it helps.";
cin.get();
}
Code:
return 0;
Code:
cin.get();
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