I/O and Program Control Statements

1
I/O and Program Control Statements

• Dick Steflik

2
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 (,-,,ltlt,gtgt)

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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 ltiostreamgt
• if you are not using a namespace
• include ltiostream.hgt
• or tell the compiler explicitly
• stdcout ltlt ...

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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.

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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)

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the insertion operator ltlt...

• For iostream the shift left operator ltlt has
  been overloaded and is called insertion
• ltlt is used to insert (write) characters into the
  stream being used
• cout ltlt Dick Steflik
• inserts Dick Steflik into the console output
  stream
• cout ltlt your grade is ltlt grade

7
the extraction operator gtgt...

• For iostream the shift right operator gtgt has
  been overloaded and is called extraction
• gtgt is used to extract (read) information from the
  console input stream (keyboard) and assign it to
  program variables
• int x cin gtgt x
• read an integer from the input stream into the
  variable x

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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 ltlt setbase(8) ltlt n // will cause n to be
  printed out as an octal number
• cout ltlt oct ltlt n // will accomplish the same
  thing
• cout ltlt hex ltlt n // will print n as a
  hexadecimal number
• cout ltltdec ltlt n // will print n as a decimal
  number
• setw or width - will set the field width of
  subsequent fields
• cout .setw(10) coutltlt n // n will be printed
  right justified in a field 10 char wide
• cout ltlt setw(12) ltlt n // same thing

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Formatting flags

• setf, unsetf and flags control I/O flag settings
• iosskipws - skip white space on input stream
• iosleft - left justify output in a field, pad
  to right (if needed)
• iosright - right justify in a field, pad on
  left (if needed)
• iosinternal - left justify the sign, right
  justify value
• iosdec - treat integers as base 10
• iosoct - treat integers as octal
• ioshex - treat integers as hexadecimal
• iosshowbase - display the base ahead of number
  (0 for octal, 0x for hex)
• iosshowpoint - display floating point numbers
  with a decimal point
• iosfixed - display floating point numbers with
  specified number of decimal digits
• iosuppercase - show upper case (ABCDEF) letters
  in hexadecimal numbers
• iosscientific - show floating point numbers in
  scientific notation

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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 ltlt setf( ioshex iosuppercase) ltlt x
• displays x in hexadecinal format with uppercase
  letters for letters

11
Deitel Deitel

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