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Friday, September 30, 2016

Learn the C++ Basic Syntax

In the previous article you wrote your first C++ program. But if you want to write more C++ programs then you will need to learn the syntax of C++ Programming Language.

C++ Keywords

Any Programming Language has a list of keywords. C++ Keywords are list of reserved words for this programming language. Each keyword has a special meaning and it can't be changed by the programmer. The list of the C++ keywords are:
 asm else new this
 auto enum operator throw
 bool explicit private true
 break export protected try
 case extern public typedef
 catch false register typeid
 char float reinterpret_cast typename
 class for return union
 const friend short unsigned
 const_cast goto signed using
 continue if sizeof virtual
 default inline static void
 delete int static_cast volatile
 do long struct wchar_t
 double mutable switch while
 dynamic_cast namespace template  

Now above list of keywords doesn't tell you anything. Do not worry about it. It's absolutely normal, because we will learn the meaning and usage of the most important part of C++ keywords in this tutorial. You just have to remember that we can't use these keywords to name constants, variables or any other identifier's name.
Now, let's take a look on the program written in the previous article:

//include a header file from Standard Library
#include <iostream>
using namespace std;
//the work of the program starts from function called 'main'
int main()
 //use standard(console) to output  message "Hello World"
 cout  << "Hello  world" << endl;
 //wait for user to press a key
 //return a value to the system  when program finishes its execution successfully
 return 0;
This is a basic program and now we will explain the basic syntax used in this program.

What is #include ?

The program always starts with some lines containing include keywords. The include keyword is preceded by the "#" symbol. The symbol "#" means that it is a preprocessor directive. This will be discussed later in "C++ Advanced" section of this tutorial. It is important to know that if you want to use any file from Standard Library, your include line should look like this:

What is 'using namespace std' ?

By writing "using namespace <some_namespace>" we can use that namespace in our program. For example if we want to use "std" namespace then we have to write below line
usingnamespace std;
If you want to use any symbol from std namespace by writing below line, all symbols in that namespace will become visible without adding the namespace prefix. A symbol may be for instance a function, class or a variable. So after writing "using namespace std" the symbol "cout" can be used directly as shown below:
cout<<"Welcome to TutorialCup";
But if you are not writing "using namespace std" then to get above output, you need to write code as below
std::cout<<"Welcome to TutorialCup";

What is a main() function in C++ ?

Any function in C++ is a block of the instructions to the compiler. The block of instructions is "highlighted" within "{ }" characters. For example:

#include <iostream>
int main()
{//start of block

 //block of instructions for main  functions

}//end of block
Main function is the starting function of any C++ program. Compiler first find and execute main function in the program.
We will discuss the syntax of C++ Programming language step by step in next articles. Now it's just a basic explanation of the HelloWorld program.


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