cin

Pre-defined stream

• Summary
• Data Type and Member Function Indexes
• Synopsis
• Description
• Example
• See Also
• Standards Conformance

Controls input from a stream buffer associated with the object stdin declared in <cstdio>.

None

#include <iostream>
extern istream cin;
istream cin;

The object cin controls input from a stream buffer associated with the object stdin declared in <cstdio>. By default, the standard C and C++ streams are synchronized, but you can improve performance by using the ios_base member function synch_with_stdio to desynchronize them.

After the object cin is initialized, cin.tie() returns &cout, which implies that cin and cout are synchronized.

//
// cin example #1
//
#include <iostream>

void main ( )
{
  using namespace std;
   
  int i;
  float f;
  char c;

  //read an integer, a float and a character from stdin 
  cin >> i >> f >> c;

  // output i, f and c to stdout
  cout << i << endl << f << endl << c << endl;   
}

//
// cin example #2
//
#include <iostream>

void main ( )
{
  using namespace std;

  char p[50];

  // remove all the white spaces 
  cin >> ws;

  // read characters from stdin until a newline
  // or 49 characters have been read
  cin.getline(p,50);

  // output the result to stdout
  cout << p;   
}

When inputting " Grendel the monster" (newline) in the previous test, the output is "Grendel the monster". The manipulator ws removes spaces.

basic_istream(3C++), iostream(3C++), basic_filebuf(3C++), cout(3C++), cerr(3C++), clog(3C++), wcin(3C++), wcout(3C++), wcerr(3C++), wclog(3C++), ios_base(3C++), basic_ios(3C++)

Working Paper for Draft Proposed International Standard for Information Systems--Programming Language C++, Section 27.3.1

ANSI X3J16/ISO WG21 Joint C++ Committee