I/O and Program Control Statements

Dick Steflik

Overloading

• C++ provides two types of overloading– function overloading

• the ability to use the same function name to have multiple definitions

– operator overloading• the ability to define multiple definitions for any

(almost) of the graphical symbols used for operators (+,-,*,<<,>>…)

But First... I/O

• To enable your program to do input and output you must include the IOSTREAM header file– if you are using namespace std

• #include <iostream>

– if you are not using a namespace• #include <iostream.h>

– or tell the compiler explicitly• std::cout << ……...

more on I/O...

• Once iostream has been included we can use the predefined objects cout, cin and cerr.

• cout, cin and cerr are predefined objects of class iostream; they are not I/O statements in the sense of program statements, they are objects that we will invoke methods on.

more on I/O...

• The class iostream allows us to define something called a stream, a stream is nothing more than a sequence of bytes– in the case of cin it is the sequence of bytes

coming from sysin (the keyboard)– in the case of cout it is the sequence of bytes

being transferred to sysout (the display)

the insertion operator <<...

• For iostream the “shift left” operator << has been overloaded and is called insertion

• << is used to insert (write) characters into the stream being used– cout << “Dick Steflik”;

• inserts “Dick Steflik” into the console output stream

– cout << “your grade is : “ << grade;

the extraction operator >>...

• For iostream the “shift right” operator >> has been overloaded and is called extraction

• >> is used to extract (read) information from the console input stream (keyboard) and assign it to program variables– int x ; cin >> x;

• read an integer from the input stream into the variable x

iomanip.h

• iomanip.h provides a number of stream manipulators that when placed inline with our cin/cout method calles affect the way the commands are handled– setbase(n) will set the base to be used for insertion and extraction to n

• cout << setbase(8) << n; // will cause n to be printed out as an octal number

• cout << oct << n; // will accomplish the same thing

• cout << hex << n; // will print n as a hexadecimal number

• cout <<dec << n; // will print n as a decimal number

– setw or width - will set the field width of subsequent fields• cout .setw(10); cout<< n; // n will be printed right justified in a field 10 char wide

• cout << setw(12) << n; // same thing

Formatting flags• setf, unsetf and flags control I/O flag settings

• ios::skipws - skip white space on input stream

• ios::left - left justify output in a field, pad to right (if needed)

• ios::right - right justify in a field, pad on left (if needed)

• ios::internal - left justify the sign, right justify value

• ios::dec - treat integers as base 10

• ios::oct - treat integers as octal

• ios::hex - treat integers as hexadecimal

• ios::showbase - display the base ahead of number (0 for octal, 0x for hex)

• ios::showpoint - display floating point numbers with a decimal point

• ios::fixed - display floating point numbers with specified number of decimal digits

• ios::uppercase - show upper case (ABCDEF) letters in hexadecimal numbers

• ios::scientific - show floating point numbers in scientific notation

Using Formatting flags

• The flags member function must specify a value for each formatting flag (seldom used)

• The setf member function and the stream manipulator setiosflags are used to set one or more formating flags; likewise unsetf and resetioflags will reset one or more formatting flags.– cout << setf( ios::hex | ios::uppercase) << x;

• displays x in hexadecinal format with uppercase letters for letters

Deitel & Deitel

• Review Chapter 11 of the Deitel & Deitel C++ How to Program book for a good discussion on Stream I/O