using Declarations

Lines 6–8

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are using declarations that eliminate the need to repeat the std:: prefix as we did in earlier programs. We can now write cout instead of std::cout, cin instead of std::cin and endl instead of std::endl, respectively, in the remainder of the program.

In place of lines 6–8, many programmers prefer to provide the using directive

which enables a program to use all the names in any standard C++ header (such as <iostream>) that a program might include. From this point forward in the book, we’ll use the preceding directive in our programs. In Chapter 21, Other Topics, we’ll discuss some issues with using directives in large-scale systems.