The document provides an introduction to preprocessors in C++, detailing the role of preprocessor directives that begin with a ‘#’ symbol, such as macros, file inclusion, and conditional compilation. It explains the use of the iostream and iomanip libraries for handling input/output operations and formatting in C++ programs. Key aspects include how to define macros, include standard and user-defined files, and utilize various I/O manipulators for output customization.

1. Presented By:
Deepshikha Haritwal
Satya Prakash Ranjan

2.  Introduction to preprocessors
 Various preprocessors directives
 The IOSTREAM library
 The IOMANIP library

3.  Preprocessors are programs that processes the
source code before actual compilation of the
program.
 The preprocessors directives always begin with a ‘#’
symbol.
 The ‘#’ symbol at beginning of statement in a c++
program indicates that it is a preprocessor directive.

4.  The various kinds of preprocessor directives that
preprocessor looks for are:
 Macros
 File inclusion
 Conditional compilation

5.  Macros are the piece of code in program which is
given a name.
 Whenever this name is encountered in the program
the compiler replaces the name with the actual piece
of code.
 #define directive is used for this purpose.

6. #include<iostream>
#define LIMIT 5
using namespace std;
int main()
{
for(int i=0;i<LIMIT;++i)
{
cout<<i<<“n”;
}
return 0;
}

7.  This type of preprocessor directive tells the compiler
to include a file in the source code program.
 There are two types of files that can be included in
the source program:
 1. Header files or Standard files
 2. User Defined files

8.  To include header files we write:
 #include<filename>
The <> brackets both delimit the filename and indicate that the
file is to be found in one of the standard directories of system.
 To include user defined files we write:
 #include “filename”
Filename within “ ” indicate that it is a user defined file.

9.  These directives helps to compile a specific portion of
the program or to skip the compilation of some
specific part of the program based on some
conditions.
 “ifdef”, “endif”, “ifndef” are some of the
preprocessing commands that helps achieving this
purpose.

10.  #ifdef macroname
Statement 1;
Statement 2;
.
.
.
.
#endif
• If the macroname is defined then the block of
statement will be executed otherwise compiler will
skip the execution of these statements.

11.  C++ I/O libraries provides an interface between the
program and the hardware devices that make up the
computer system.
 The IOSTREAM header file of c++ defines a
collection of stream classes that are capable of input,
output or both input and output.

12.  CIN OBJECT:
 It represents the standard input stream.
 It is used along with the extraction operator(>>)
 Example :
int a;
cin>>a;
 COUT OBJECT:
 It represents the standard output stream.
 It used along with the insertion operator(<<)
 Example :
int a=15;
cout<<“Value of a:”<<a;

13.  CERR OBJECT:
 It is an object of the class ostream.
 It represents the standard error stream.
 Example:
cerr<<“system being rebooted in 2 minutesn”;
• CLOG OBJECT:
• It is an object of the class ostream.
• It represents the standard logging stream.
• Example :
clog<< Username<<“has logged into system”;

14.  The iomanip library defines a collection of I/O
stream manipulators to modify the behavior of
insertions and extractions.
 It is a library that is used to manipulate the output of
c++ program.

15.  Setw(int w): it sets the field width to w.
 Setfill(char c): it sets the fill character to c.
 Setbase(int b): used to set the base field to one of the
possible values according to argument base.
 Setprecision(int d): sets the number of places of
accuracy to d.
 Scientific: displays the floating point values in
scientific notation.
 Fixed: displays the floating point values in decimal
notation

16.  Showpos: positive numbers are
displayed with a leading + sign.
 Showbase: octal numbers are displayed
preceded with 0 and hexadecimal
numbers are displayed preceded with
0x.
 Boolalpha: displays logical values
symbolically as true and false.
 Noboolapha : displays logical values as 0
and 1.