Input Output Formats In C++

Introduction: 

• C++ language describes input/output using iostream.h.
• The standard input/output library for c described by the header stdio.h is still available in C++.
• The header stream.h was used on systems before release 2.0 and is still available under many C++ systems.

Input and Output Operator: 

• << - for Printing Variables
• >> - for Reading Variables

Output class: 

• The output is inserted into an object of type ostream.
• It is declared in the header file iostream.h.
• An operator << is loaded in this class to perform output conversions from standard types
• The overloaded left shift operator is called the “insertion or put to operator”.
• The standard output ostream corresponding to stdout is cout.
• The standard output ostream corresponding to stderr is cerr.

Output cout Syntax: 

cout<<?var?<<var<<?\n?; 

Public members: 

ostream& operator<<int(i);
ostream& operator<<(long i);
ostream& put(char c);
ostream& write(const char *p, int n);
ostream& flush(); 

The member function flush() forces the stream to be written. 

Formatted output & iomanip.h

The put to operator << produces by default the minimum number of characters.

Example: 

int i=8,j=9;
cout<<i<<j;
cout<<i<<? ?j;
cout<<?i=?<<i<<?j=?<<j;

Immediately prints the line:

x=1; 

User-defined types: output: 

It has typically been printed by creating a member function print().

ostream& operator<<(ostream& out, dock x) {
    for (int i = 0; i < 52; ++i) {
        if (i % 13 == 0)
            out << endl;
        out << x.d[i];
    }
    Return out;
}

The input class isstream: 

• An operator >> is overloaded in istream to perform input conversions to standard types
• The overloaded right shift operator is called the extraction or get from the operator.
• The standard input istream corresponding to stdin is cin.

Input cin Syntax:

cin>>var>>char; 

Public members: 

istream& operator>>(int& i);
istream& get(char& c);
istream& read(char* s,int n); 

Useful member function: 

int gcount();
stream& ignore (int n=1,int delimeter=EOF); 

Files Input and Output

• C have stdin,stdout,stderr.
• In addition, systems may define other standard files such as stdprn & stdaux.
• File I/O is handled by including fstream.h
• It contains the classes ofstream and ifstream

Ifstream();
Ifstream(const char *, int=ios::in);
Ofstream();
Ofstream(const char *, int =ios::out); 

Standard files format:

Standard File Modes:

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