C++ Basics Which May Have Been Skipped In Class

• White-space is completely ignored by compiler : Not True. There are few restrictions apply to this rule. e.g.
  • Preprocessor directives must be in same line.
  • ‘cout’ could not be broken.
• Cout, Cin are objects : These are overloaded. Cout – ‘<<‘ (Put to or insertion operation) and ‘>>’ (extraction or get operator).
• Directives :
  • Preprocessor Directives :
    • Starts with #
    • It is an instruction to compiler’s preprocessor part.
    • usually adds header type file are included using it.
  • Using Directive :
    • C++ program can be divided into different name spaces. using tells the name of namespace.
    • Namespace is a part of program in which some names are recognised, outside which they are unknown.
    • e.g. using namespace std; –> In ‘std’ namespace various program components such as cout are declared.
    • If we don’t use ‘std’ then we have add std name to many program elements e.g. – std::cout << “xyz”;
• Header files (include files) :
  • Newer standard c++ header files don’t have a file extension, but older from the time of c have extension ‘.H’.
  • Header files contains names and types of library functions.
• Integers :
  • Commonly used is ‘int’ but there are many sized of ‘int’ available (depends on compiler).
  • Amount of memory occupied by the integer type is System Dependent. A 32 bit system have 32 bit int (4 bytes, Range : -2,147,483,648 to 2,147,483,647).
  • The range occupied by various types are listed in the header file ‘LIMITS’.
• Other integer types :
  • Long, Short, Char are Integer types and have fixed size as opposed to int.
  • Long is of  4 bytes. This helps on systems where int is limited to 2 bytes.
  • Short is of 2 bytes ( Range : -32,768 to 32,767). This is only used to save some memory. But we rarely use it because int is faster to access than short.
  • Constant of type long can be declared as :
    • longvar  = 76L;
  • Many compilers provide various sizes of int : These types are preceded by two underscores. They are __int8, __int16, __int32 and __int64. The __int8 corresponds to a char.
  • For bigger char size c++ have type wchar_t. Because in 1 byte we cannot accommodate many language characters.
• Escape Sequences :

\xdd is used to represent character above 127 range in hexadecimal notation e.g. \xB2

• Declaration and Definitions : A declaration introduces a variable’s name into a program and specifies its type. However, a declaration also sets aside memory for the variable, it is also called a definition.
• The ‘endl’ manipulator : endl inserts linefeed into the stream.
  • Manipulators are instructions to the the output stream, that modify the output in various ways.
  • endl and ‘\n’ difference : endl causes the output buffer to be flushed.
• Library Functions : These functions perform file access, mathematical computations and data conversion. These functions are stored in library files having extension ‘.LIB’.
• Header files and Library files : Header files contains the names and types of the functions and other elements in the library files.
• Two ways of #include
  • #include <header.h> : Starts search from default INCLUDE  directory.
  • #include “header.h” : Starts search from current directory.
  • No difference between the two. But if we tell the place of header file then the compilation process becomes somewhat fast.
• ‘const’ keyword is used to stipulates that the value of variable will not change.