library

Library is the collection of sub programs (functions) used to develop other programs and software.
Libraries are not independent program rather they are helper code (statements) used in other independent programs. The C++ library of functions stores functions of some category (mathematical function,string function,etc) under separate files known as header files.

So the library contains standard functions which make a program easy to understand.

Header files provide function prototype,definition for library functions EX. stdio.h, conio.h,math.h, string.h, iostream.h.

Each and every string is ended with \0(\zero) & is also called nul character.