Question

Define these elements written before the program.

Answer 1

#include
#include < conio.h>

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These are the header files for a program.Header files are special pre-defined files in c++, for some special specified purpose . It contains definition of function as well as object that is used in a program .
If you are not givingheader file before any c++ program then it will an error for prototype.


What is basically "namespace" in using namespace std?
In general, a namespace is a container for a set of identifiers (also known as symbols, names). Namespaces provide a level of direction to specific identifiers, thus making it possible to distinguish between identifiers with the same exact name. For example, a surname could be thought of as a namespace that makes it possible to distinguish people who have the same given name. In computer programming, namespaces are typically employed for the purpose of grouping symbols and identifiers around a particular functionality.