Sunday, November 7, 2010



Microsoft Visual C++ Express Edition Installation:

1. Go to the Microsoft Downloads Page and download Microsoft Visual C++ 2008 Express Edition.

2. Run vcsetup.exe. It is an online installer.

3. Click Next



4. Accept license agreement and click Next:

5. You may skip these products for now, but they can be added in the future. Click Next:

6. Remember, where you are installing Microsoft Visual Studio and click Install button:

7. Wait, while setup download and install files:

8. After setup is complete, press Exit:

9. Close all active applications and click on Restart Now button:  

Running Microsoft Visual Studio Express Editions

  1. Go to the Start - All Programs - Microsoft Visual C++ 2008 Express Edition and run Microsoft Visual C++ 2008 Express Edition. You should see the following: 

2. Go to the File - New - Project...:

3. Choose Visual C++ - General - Empty project. Call your project "HelloWorldProject" and the solution would be "HelloWorldSolution":

4. Click with right button on the Source Files folder of your project. Choose Add - New Item...:

5. Choose Visual C++ - C++ file (.cpp) and call it "HelloWorldApp":

6. Type a code from the image below into the Code Editor Window:

7. Press the Run button:

8. You should see a warning. Check "Do not show this dialog again" checkbox and click Yes:  

9. You should see a console window:

How to write ANSI C programs by using Visual C++ .NET or Visual C++ 2010

The best way to create new projects is by using the Visual C++ application wizards. Visual C++ application wizards work with the application frameworks and libraries to create starter programs for you.

To create ANSI C programs by using the Visual C++ application wizards in the Visual Studio .NET or Visual Studio 2005 IDE, follow these steps:
  1. Start Microsoft Visual Studio .NET or Microsoft Visual Studio 2005.
  2. On the File menu, point to New, and then click Project.
  3. Under Project Types, click Visual C++ Projects.

    Note In Visual Studio 2005, click Visual C++ under Project Types.
  4. Under Templates, click Win32 Project.
  5. In the Name text box, type FirstApplication.
  6. In the Location text box, type C:\Test, and then click OK.

    The Win32 Application Wizard - FirstApplication dialog box appears.
  7. In the Win32 Application Wizard dialog box, click Application Settings in the left pane.
  8. Under Application Type, click to select any of the following options:
    • Console application: Creates a simple console application. The application files include a .cpp file that contains an empty main function.
    • Windows application: Creates a simple Microsoft Windows-based application. The application files include a ProjectName.cpp file that contains a _tWinMain function. You can use this type of application to perform graphical user interface (GUI) based programming.
    • DLL: Creates a 32-bit Windows-based DLL application project.
    • Static library: Creates a 32-bit Windows-based DLL application project.
    To create a simple "Hello World!" program, click to select Console application.
  9. Under Additional options, click to select the Empty project check box.

    Note To create a simple "Hello World!" program, do not select this check box. Instead, let the wizard generate the code for you.
  10. Click Finish.
  11. In Solution Explorer, right-click the Source Files folder, point to Add, and then click Add New Item.
  12. In Add New Item - FirstApplication dialog box, click C++ File (.cpp) under Templates.
  13. In the Name text box, type Test.c, and then click Open.
  14. In the Test.c code window, paste the following code:

    #include"stdio.h"

int main()
{
 printf("Hello World\n");
 return 0;
}
    #include is a preprocessor directive that tells the compiler to put code from the stdio.h header file into your program. If you include header files, you can gain access to standard library functions. For example, your application must have access to the stdio.h header file to use the printf function.
  15. On the Build menu, click Build Solution.
  16. Press CTRL+F5 to run the application. You receive the following message in a Command Prompt window:
    Hello World
    Press any key to continue


Programming C++
//Program of factorial
#include
#include

int factorial(int n)
{
 int x;
 if(n==1)
   return 1;
 x=n*factorial(n-1);
 return x;
}

void main()
{
 clrscr();
 int n,result;
 cout<<"Enter your number to be factorial: ";
 cin>>n;
 result=factorial(n);
 cout<<"Factorial is: "<
 getch();
}
//Program of Fibonacci
#include
#include

int fibo(int n)
{
 int x;
 if(n==0)
   x=0;
 else if(n==1)
   x=1;
 else
   x=fibo(n-1)+fibo(n-2);
   return (x);
}

void main()
{
  clrscr();
  int n,x;
  cout<<"Enter your number to be fibonacci: ";
  cin>>n;
  x=fibo(n);
  cout<<"The fibonacci is: "<
  getch();
}
//////////////////////////////////////

//Program to set max to the maximum and min to the minimum of a[1:n]
//Algorithm StraightMaxMin(a,n,max,min)

#include
#include

void main()
{
clrscr();
int n,i,max,min,a[20];
max=min=a[0];

cout<<"How many numbers? ";
cin>>n;
cout<<"Enter your numbers: ";
for(i=0;i
    cin>>a[i];
for(i=0;i
    {
    if(a[i]>max)
        max=a[i];
    else
    min=a[i];
/*    if(a[i]
        min=a[i];*/
    }
cout<<"The max is: "<
cout<<"\nThe min is: "<
getch();
}
///////////////////////////////////////////////////////
// *****************************************
//        cplusplus language tutorial
//                section 2.1
//
//            "Guess the number"
// Shows:
//   - do-while
//   - if-else
//
// Briefing:
//  The computer generates a random number
//  between 1 and MAX_RANGE. The user must
//  guess the number. Each time the user
//  makes an attempt the computer tells if
//  the number is greater or less than.
// *****************************************

#include
#include
#include

// Define the greatest possible value:
#define MAX_RANGE 100

main ()
{
  int counter=0;
  long value,input;

  srand ( time (NULL) );         // Initialize random generator
  value = rand()%MAX_RANGE+1;    // Get random between 1 and MAX_RANGE

  cout << "\nInsert a value between 1 and " << MAX_RANGE << " : ";

  do {

    cin >> input;                // Get user input
    counter++;                   // increase attempts counter

    if (value>input)             // is value grater than the input?
      cout << "Value is greater than " << input << ". Try again : ";

    else if (value
      cout << "Value is less than " << input << ". Try again : ";

    else {                       // else it is the correct number!
      cout << "That's right! Value was " << input;
      cout << "\nYou have needed " << counter <<" attempts.";
      }

  } while (value!=input);
  return 0;

}
////////////////////////////////////////////////////
Class and Object:
fjkdffhfjh
File
C++ File I/O Classes and Functions:
   There are 3 File I/O classes in C++ which are used for File Read/Write operations. They are
  • ifstream         -  Can be used for File read/input operations
  • ofstream        -  Can be used for File write/output operations
  • fstream          -  Can be used for both read/write c++ file I/O operations
  The most important methods which will be used for any file operations are:
  1. fstream::open method - to open the file
  2. fstream::Operator >> and fstream::Operator <<  - For reading from or writing to the file.
  3. fstream::close  - Flushes all buffer and close the file
Reading a text file using fstream class:
  There are several ways of reading the text from a file. But all of them have a common approach as follows.
  1. Open the file
  2. Read the data
  3. Close the file
   This sample code snippet explains how to use the c++ file i/o stream operators to read data from a file. In all cases the header file fstream.h must be included.

    #include
    int main()
    {
        char str[2000];
        fstream file_op("c:\\test_file.txt",ios::in);
        while(file_op >> str)
        cout << str ;

        file_op.close();

        return 0;
    }

   The class fstream, which is used above is the one which is commonly used for c++ file i/o manipulations. The constructor of fstream takes 2 parameters. One is the file path and the second is the File Open mode. There are several open modes, each of them with a different purpose. Some of them are ios::in for reading, ios::out for writing, ios::app for appending to the end of file, ios::binary for opening in binary mode etc.,
   Now for the purpose of this article, as the data is read from the file, the flag ios::in is used. After this,  the read operation is continued till the end of the file. The while loop ensures a continuous read till the end of the file or it encounters any abnormal break. If the program is built and run , it displays all the data read from the file. The C++ File I/O read job is done.
   But if we look at the output closely, there is a draw back in using this stream operator read. The output misses the white spaces and the end of line characters. In order not to miss these characters we can either use fstream::get() or fstream::getline() methods. Here is the example for using fstream getline method.

 #include
    int main()
    {
        char str[2000];
        fstream file_op("c:\\test_file.txt",ios::in);
        while(!file_op.eof())
        {
              file_op.getline(str,2000);
              cout <
        }         file_op.close();
        cout <

        return 0;
    }

Writing to a text file using fstream class:
   Writing to a text file can also be achieved with the stream operators. This also follows the same order of operations, though with a slight difference.
      1. open a file - in write mode
      2. Write to a file
      3. close the file
   Look at the following sample code to see the difference.

    #include
    int main()
    {
        fstream file_op("c:\\CoderSource_file.txt",ios::out);

        file_op<<"Test Write to file";
        file_op.close();
        return 0;
    }

   To modify the data or to seek to a different position inside the file, the c++ file i/o class fstream provides member functions like seekg() etc., These functions can be used to relocate the record insert position to the desired locations.
   After all the C++ File I/O operations we do a fstream::close(), to close the file pointer. This is not mandatory. Even if this function is not called by the application, the destructor of the fstream class will close the file when the object goes out of scope.




File Operation:

Input/Output with files

Published by Juan Soulie
Last update on Oct 9, 2010 at 6:48am UTC
C++ provides the following classes to perform output and input of characters to/from files:

  • ofstream: Stream class to write on files
  • ifstream: Stream class to read from files
  • fstream: Stream class to both read and write from/to files.


These classes are derived directly or indirectly from the classes istream, and ostream. We have already used objects whose types were these classes: cin is an object of class istream and cout is an object of class ostream. Therfore, we have already been using classes that are related to our file streams. And in fact, we can use our file streams the same way we are already used to use cin and cout, with the only difference that we have to associate these streams with physical files. Let's see an example:

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// basic file operations
#include 
#include 
using namespace std;

int main () {
  ofstream myfile;
  myfile.open ("example.txt");
  myfile << "Writing this to a file.\n";
  myfile.close();
  return 0;
}
 
[file example.txt]
Writing this to a file.


This code creates a file called example.txt and inserts a sentence into it in the same way we are used to do with cout, but using the file stream myfile instead.

But let's go step by step:

Open a file


The first operation generally performed on an object of one of these classes is to associate it to a real file. This procedure is known as to open a file. An open file is represented within a program by a stream object (an instantiation of one of these classes, in the previous example this was myfile) and any input or output operation performed on this stream object will be applied to the physical file associated to it.

In order to open a file with a stream object we use its member function open():


open (filename, mode);


Where filename is a null-terminated character sequence of type const char * (the same type that string literals have) representing the name of the file to be opened, and mode is an optional parameter with a combination of the following flags:

ios::inOpen for input operations.
ios::outOpen for output operations.
ios::binaryOpen in binary mode.
ios::ateSet the initial position at the end of the file.
If this flag is not set to any value, the initial position is the beginning of the file.
ios::appAll output operations are performed at the end of the file, appending the content to the current content of the file. This flag can only be used in streams open for output-only operations.
ios::truncIf the file opened for output operations already existed before, its previous content is deleted and replaced by the new one.


All these flags can be combined using the bitwise operator OR (|). For example, if we want to open the file example.bin in binary mode to add data we could do it by the following call to member function open():

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ofstream myfile;
myfile.open ("example.bin", ios::out | ios::app | ios::binary);


Each one of the open() member functions of the classes ofstream, ifstream and fstream has a default mode that is used if the file is opened without a second argument:

classdefault mode parameter
ofstreamios::out
ifstreamios::in
fstreamios::in | ios::out


For ifstream and ofstream classes, ios::in and ios::out are automatically and respectively assumed, even if a mode that does not include them is passed as second argument to the open() member function.

The default value is only applied if the function is called without specifying any value for the mode parameter. If the function is called with any value in that parameter the default mode is overridden, not combined.

File streams opened in binary mode perform input and output operations independently of any format considerations. Non-binary files are known as text files, and some translations may occur due to formatting of some special characters (like newline and carriage return characters).

Since the first task that is performed on a file stream object is generally to open a file, these three classes include a constructor that automatically calls the open() member function and has the exact same parameters as this member. Therefore, we could also have declared the previous myfile object and conducted the same opening operation in our previous example by writing:

ofstream myfile ("example.bin", ios::out | ios::app | ios::binary);


Combining object construction and stream opening in a single statement. Both forms to open a file are valid and equivalent.

To check if a file stream was successful opening a file, you can do it by calling to member is_open() with no arguments. This member function returns a bool value of true in the case that indeed the stream object is associated with an open file, or false otherwise:

if (myfile.is_open()) { /* ok, proceed with output */ }


Closing a file

When we are finished with our input and output operations on a file we shall close it so that its resources become available again. In order to do that we have to call the stream's member function close(). This member function takes no parameters, and what it does is to flush the associated buffers and close the file:

myfile.close();


Once this member function is called, the stream object can be used to open another file, and the file is available again to be opened by other processes.

In case that an object is destructed while still associated with an open file, the destructor automatically calls the member function close().

Text files

Text file streams are those where we do not include the ios::binary flag in their opening mode. These files are designed to store text and thus all values that we input or output from/to them can suffer some formatting transformations, which do not necessarily correspond to their literal binary value.

Data output operations on text files are performed in the same way we operated with cout:

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// writing on a text file
#include 
#include 
using namespace std;

int main () {
  ofstream myfile ("example.txt");
  if (myfile.is_open())
  {
    myfile << "This is a line.\n";
    myfile << "This is another line.\n";
    myfile.close();
  }
  else cout << "Unable to open file";
  return 0;
}
 
[file example.txt]
This is a line.
This is another line.


Data input from a file can also be performed in the same way that we did with cin:

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23		 
// reading a text file
#include 
#include 
#include 
using namespace std;

int main () {
  string line;
  ifstream myfile ("example.txt");
  if (myfile.is_open())
  {
    while ( myfile.good() )
    {
      getline (myfile,line);
      cout << line << endl;
    }
    myfile.close();
  }

  else cout << "Unable to open file"; 

  return 0;
}
 
This is a line.
This is another line.


This last example reads a text file and prints out its content on the screen. Notice how we have used a new member function, called good() that returns true in the case that the stream is ready for input/output operations. We have created a while loop that finishes when indeed myfile.good() is no longer true, which will happen either if the end of the file has been reached or if some other error occurred.

Checking state flags

In addition to good(), which checks whether the stream is ready for input/output operations, other member functions exist to check for specific states of a stream (all of them return a bool value):

bad()
Returns true if a reading or writing operation fails. For example in the case that we try to write to a file that is not open for writing or if the device where we try to write has no space left.
fail()
Returns true in the same cases as bad(), but also in the case that a format error happens, like when an alphabetical character is extracted when we are trying to read an integer number.
eof()
Returns true if a file open for reading has reached the end.
good()
It is the most generic state flag: it returns false in the same cases in which calling any of the previous functions would return true.


In order to reset the state flags checked by any of these member functions we have just seen we can use the member function clear(), which takes no parameters.

get and put stream pointers

All i/o streams objects have, at least, one internal stream pointer:

ifstream, like istream, has a pointer known as the get pointer that points to the element to be read in the next input operation.

ofstream, like ostream, has a pointer known as the put pointer that points to the location where the next element has to be written.

Finally, fstream, inherits both, the get and the put pointers, from iostream (which is itself derived from both istream and ostream).

These internal stream pointers that point to the reading or writing locations within a stream can be manipulated using the following member functions:

tellg() and tellp()

These two member functions have no parameters and return a value of the member type pos_type, which is an integer data type representing the current position of the get stream pointer (in the case of tellg) or the put stream pointer (in the case of tellp).

seekg() and seekp()

These functions allow us to change the position of the get and put stream pointers. Both functions are overloaded with two different prototypes. The first prototype is:


seekg ( position );
seekp ( position );


Using this prototype the stream pointer is changed to the absolute position position (counting from the beginning of the file). The type for this parameter is the same as the one returned by functions tellg and tellp: the member type pos_type, which is an integer value.

The other prototype for these functions is:


seekg ( offset, direction );
seekp ( offset, direction );


Using this prototype, the position of the get or put pointer is set to an offset value relative to some specific point determined by the parameter direction. offset is of the member type off_type, which is also an integer type. And direction is of type seekdir, which is an enumerated type (enum) that determines the point from where offset is counted from, and that can take any of the following values:

ios::begoffset counted from the beginning of the stream
ios::curoffset counted from the current position of the stream pointer
ios::endoffset counted from the end of the stream


The following example uses the member functions we have just seen to obtain the size of a file:

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// obtaining file size
#include 
#include 
using namespace std;

int main () {
  long begin,end;
  ifstream myfile ("example.txt");
  begin = myfile.tellg();
  myfile.seekg (0, ios::end);
  end = myfile.tellg();
  myfile.close();
  cout << "size is: " << (end-begin) << " bytes.\n";
  return 0;
}
 
size is: 40 bytes.


Binary files

In binary files, to input and output data with the extraction and insertion operators (<< and >>) and functions like getline is not efficient, since we do not need to format any data, and data may not use the separation codes used by text files to separate elements (like space, newline, etc...).

File streams include two member functions specifically designed to input and output binary data sequentially: write and read. The first one (write) is a member function of ostream inherited by ofstream. And read is a member function of istream that is inherited by ifstream. Objects of class fstream have both members. Their prototypes are:


write ( memory_block, size );
read ( memory_block, size );


Where memory_block is of type "pointer to char" (char*), and represents the address of an array of bytes where the read data elements are stored or from where the data elements to be written are taken. The size parameter is an integer value that specifies the number of characters to be read or written from/to the memory block.

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// reading a complete binary file
#include 
#include 
using namespace std;

ifstream::pos_type size;
char * memblock;

int main () {
  ifstream file ("example.bin", ios::in|ios::binary|ios::ate);
  if (file.is_open())
  {
    size = file.tellg();
    memblock = new char [size];
    file.seekg (0, ios::beg);
    file.read (memblock, size);
    file.close();

    cout << "the complete file content is in memory";

    delete[] memblock;
  }
  else cout << "Unable to open file";
  return 0;
}
 
the complete file content is in memory


In this example the entire file is read and stored in a memory block. Let's examine how this is done:

First, the file is open with the ios::ate flag, which means that the get pointer will be positioned at the end of the file. This way, when we call to member tellg(), we will directly obtain the size of the file. Notice the type we have used to declare variable size:

ifstream::pos_type size;


ifstream::pos_type is a specific type used for buffer and file positioning and is the type returned by file.tellg(). This type is defined as an integer type, therefore we can conduct on it the same operations we conduct on any other integer value, and can safely be converted to another integer type large enough to contain the size of the file. For a file with a size under 2GB we could use int:

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int size;
size = (int) file.tellg();


Once we have obtained the size of the file, we request the allocation of a memory block large enough to hold the entire file:

memblock = new char[size];


Right after that, we proceed to set the get pointer at the beginning of the file (remember that we opened the file with this pointer at the end), then read the entire file, and finally close it:

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file.seekg (0, ios::beg);
file.read (memblock, size);
file.close();


At this point we could operate with the data obtained from the file. Our program simply announces that the content of the file is in memory and then terminates.

Buffers and Synchronization


When we operate with file streams, these are associated to an internal buffer of type streambuf. This buffer is a memory block that acts as an intermediary between the stream and the physical file. For example, with an ofstream, each time the member function put (which writes a single character) is called, the character is not written directly to the physical file with which the stream is associated. Instead of that, the character is inserted in that stream's intermediate buffer.

When the buffer is flushed, all the data contained in it is written to the physical medium (if it is an output stream) or simply freed (if it is an input stream). This process is called synchronization and takes place under any of the following circumstances:

  • When the file is closed: before closing a file all buffers that have not yet been flushed are synchronized and all pending data is written or read to the physical medium.
  • When the buffer is full: Buffers have a certain size. When the buffer is full it is automatically synchronized.
  • Explicitly, with manipulators: When certain manipulators are used on streams, an explicit synchronization takes place. These manipulators are: flush and endl.
  • Explicitly, with member function sync(): Calling stream's member function sync(), which takes no parameters, causes an immediate synchronization. This function returns an int value equal to -1 if the stream has no associated buffer or in case of failure. Otherwise (if the stream buffer was successfully synchronized) it returns 0.
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