Preprocessor , IOSTREAM Library,IOMANIP Library
- 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.