this pointer in C++

C++ uses a unique keyword called this to represent an object that invokes a member function. this pointer in C++ is a pointer that points to the object for which this function was called.

For example, the function call:

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A.max()

will set the pointer this to the address of the object A.

The starting address is the same as the address of the first variable in the class structure.

This unique pointer is automatically passed to a member function when it is called. The pointer this acts as an implicit argument to all the member functions.

Consider the following simple example:

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class ABC {    int a;    ...    ... };

The private variable a can be used directly inside a member function, like:

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a = 123;

We can also use the following statement to do the same job:

1	this -> a = 123;

Since C++ permits the use of shorthand form a = 123, we have not been using the pointer this explicitly so far.

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Understanding the program in C++

In this article we will understand the program written in C++ programming language in step-by-step manner. Consider the below simple C++ program that performs multiplication of two integers and displays the result.

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/*Program that performs multiplication of two integers and displays the result*/   //Include header files #include <iostream> #include "conio.h" using namespace std;   //main program starts from here void main() { //declare variables int result, variable1, variable2;   //assign values to variable1 and variable2 variable1 = 10; variable2 = 2;   /*Perform multiplication of variable1 and variable2. Store the result in the variable named result*/   result = variable1 * variable2;   //Display the result in the output window cout << "The result is: " << result << endl;   }

Result of the above program:

1	The result is: 20

Let us understand the above program in detail:

• Line 1 thru 2:
  This is a multiline comment. We have used it to describe the purpose of the program which is a very good programming practice
• Line 4:
  This is a single line command.
  Note: Comments are ignored by the compilers
• Line 5 thru 7:
  These are the header files that needs to be included in order to run the program successfully. These header files contains components/supporting components/functions needed by the inbuilt functions like cout, cin etc. for its execution.
  #include is known as pre-processor directives. It tell the compiler to include text from another file, stuffing it right into your source code. The whole statement #include tells the compiler to take text from the file iostream.h and stick it into your source code before the source code is compiled.
• Line 10:
  This is the main function of the program. The program execution starts from this function. The statement that belongs to main() are enclosed within a pair of braces {}
• Line 12:
  This line declares the integer variables to be used in the program. Any variable that we need to use must be declared before using it
• Line 15 thru 16:
  These two lines of code have been used to assign a value to the variables declared in the line 12
• Line 21
  Here, values stored in the variables named variable1 and variable2 are multiplied and the result is stored in the variable named result
• Line 24:
  This line uses inbuilt function “cout” to display the result of the multiplication in a specified format. “endl” is an inbuilt function that ends the current line and takes the cursor to the next line.

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