Using namespace std in c++ pdf book

After editing by nathan, it is obvious that string isnt sufficient for your prototype. Strings are words that are made up of characters, hence they are known as sequence of characters. It didnt have namespaces, stlstandard template library and many other features. Cpp programming tutorial pdf book for beginner techringe. Used to prevent name collisions when using multiple libraries, a namespace is a declarative prefix for functions, classes, types, etc. Using using how to use the std namespace david kieras, eecs department, university of michigan febrary 2015 why namespaces. Excluding the basics having to add std infront of all stl objectsfunctions and less chance of conflict if you dont have using namespace std it is also worth noting that you should never put. To use strings in this way, we need to include the header since it is declared in the header.

Visual quickstart guide that in order to use statements such as cin and cout without std you need to add the line using namespace std. The this pointer is passed as a hidden argument to all nonstatic member function calls and is available as a local variable within the body of all nonstatic functions. While most compilers now accept the new format, they dont require it. This is what happens if a usingdeclaration is put into a namespacedefinition. That is why we have generally included the using namespace std. The standard requires that you specify which names in a standard header file youll be using.

Lets discuss these two ways of creating string first and then we will see which method is better and why. March 16, 2016 question 2 what is the output of the following program. In general, avoid putting using directives in header files. Without this line, each keyword from the library would have to be preceded with a. This can cause name collisions because it adds every name in the std namespace to the global namespace. But using std all the time can sometimes produce rather cluttered code if you e. Consider this, there are two students in one classroom having same name for example vishal. A namespace definition begins with the keyword namespace followed by the namespace. Now i searched on web and people said that use std instead of using namespace std and replacing \n with end1. A usingdirective begins with using namespace a usingdeclaration is also distinct from an alias declaration, which gives a new name to an existing type in the same manner as typedef.

A namespace is a declarative region that provides a scope to the identifiers names of the types, function, variables etc inside it. Im trying to write a program where you can insert and display some books without using a database. All of the standard library is in one drawer, and the only way to get to. All declarations within those blocks are declared in the named scope. When programs get very large and complex, and make heavy use of libraries from a variety of sources, the possibility of name collisions rears its incredibly annoying head. My personal experience is that the pair, the vector and the map are used more often than the other stl classes, so ill frame my discussion around them. You may also leave feedback directly on github send feedback about this page title leave a comment. The idea of namespaces is quite common in computing languages. It puts the names of its members in a distinct space so that they dont conflict with the names in other namespaces or global namespace. It is a superior parameter type for functions that requires nonmodifiable string data. As giblit has already said, using using namespace std. For a small program like this one its unlikely that youll run into any problems then again, maybe not but its best to get into the habit of using the std prefix on names in the std namespace. A usingdeclaration is distinct from a using directive, which tells the compiler to look in a particular namespace when looking up any name. The compiler hasnt a clue what that type is, as std.