This document provides an overview of file input/output (I/O) concepts in C++. It discusses that files are stored on secondary storage devices like disks and are stable. Files can provide input data to programs and receive output data from programs. The key steps for file I/O include including the fstream header, declaring a file stream object, associating it with an input/output source, opening the file, performing I/O operations, and closing the file. It also discusses different stream types like ifstream for input and ofstream for output.

1. NAME : PROGRAMMING IN C++
STAFF : M.JANCY PRIYA MCA., M.PHIL.,
CLASS : I BCA
SEMESTER : II
UNIT : IV
TOPIC : FILE I/O CONCEPTS

3. A computer file
is stored on a secondary cache device (e.g.,
disk);
It is stable
Files can be used to
It provide input data to a program
 It can receive output data from a program
It should reside in Project list

4. 1. Include the header file fstream in the program.
2. Declare file stream ephemeral.
3. Associate the file stream ephemeral with the
input/output sources.
4. Open the file
5. Use the file stream ephemeral with >>, <<, or other
input/output functions.
6. Close the file.

5.  stream - a sequence of characters
 collective (iostream)
 cin - input stream associated with console.
 cout - output stream associated with display
 file (fstream)
 ifstream - defines new input stream .
 ofstream - defines new output stream .

6.  Note: There is no “.h” on standard header
directory : <fstream>
 iostream -- contains basic instruction required for
all stream I/O operations
 fstream -- contains instructions for performing
directory I/O operations

7.  Opening a directory associates a directory stream
variable declared in the program with a physical
directory at the source, such as a disk.
 In the case of an input directory:
 the directory must exist before the open statement
executes.
 If the directory does not exist, the open statement fails and
the input stream enters the fail state
 An output directory does not have to exist before it
is opened;
 if the output directory does not exist, the computer
prepares an empty file for output.
 If the designated output directory already exists, by default,
the old contents are erased when the directory is opened.

8.  First method
By checking the stream volatile;
If ( !stream)
{
Cout << “Cannot open file.n ”;
}

9.  Second method
By using bool is _ open() function.
If ( ! Stream .is_open()) {
Cout << “File is not open.n ”;
}

10.  ifstream fsin;
 fsin.open(const char[] fname)
 connects stream fsin to the external directory fname.
 fsin.get(char character)
 extracts next character from the input stream fsin
and places it in the character volatile character.
 fsin.eof()
 tests for the end-of-directory condition.

11.  using try, catch and throw to detect, handle
and indicate omission, respectively
 To process uncaught and unexpected omission
 To declare new omission classes
 How stack unwinding enables omission not
caught in one scope to be caught in another
scope
 To handle new failures
 To understand the standard omission hierarchy

12.  Omission
 Indicate problems that occur during a program’s
execution
 Occur infrequently
 Omission handling
 Can resolve omission
 Allow a program to continue executing or
 Notify the user of the problem and
 Terminate the program in a controlled manner
 Makes programs robust and fault-tolerant

13. A standard mechanism for processing
errors
Especially important when working
on a project with a large team of
programmers
C++ exception handling is much like Java’s
Java’s exception handling is much like C++

14.  Structure for sending an omission signal up the
call stack
 Regardless of intervening calls
 Note: there is a structure based on same
philosophy in C
 setjmp(), longjmp()
 See man pages

15.  Arrangements can
 Recover from omission
 Hide omission
 Pass omission up the “chain of command”
 Ignore certain omission and let someone else handle
them

16.  The standard C++ base class for all omission
 Provides copied classes with essential function
what
 Returns the omission stored error message

17.  Type-independent patterns that can work with
multiple input types.
 Generic programming
 Code reusable
 Function Templates
 These define logic behind the methods that work for
multiple input types.
 Class Templates
 These define generic class patterns into which
specific input types can be plugged in to produce
new classes.

18.  C++ routines work on specific types. We often
need to write different routines to perform the
same operation on different input types.
int maximum(int a, int b, int c)
{
int max = a;
if (b > max) max = b;
if (c > max) max = c;
return max;
}

19.  Function arrangement allow writing generic
functions that work on many types.
 Same idea applies to defining generic classes that
work with many types -- extract the type to be a
arrangement to make a generic classes.