> Programming Help. > C and C. What does "using namespace std" mean? Page 1 of 1.Introduction to C Metaprogramming: Basics. Pointers, and a possible problem - if youre not careful! Generating Random Numbers - The C Way. Professional What does 39using namespace std39 mean in C?The prefix would be the name of the library. This is a pain, and we wanted something a bit better designed in C. A namespace is a more flexible way of adding prefixes. Here, meaning of the some additional information/context is provided to prevent the ambiguity.So, we use the statement using namespace std at the beginning of our C program to use members defined in namespace std. All of the declarations in the standard C library are contained in a namespace called std. This means names defined in the header file, such as ostream, istream, cout, and cin must be qualified by " std::" when they are used by clients (see Programming Note A.3) The std namespace contains all the names defined in many of the standard C library files (such as iostream).If you do not include this using directive for the namespace std, then you can define cin and cout to have some meaning other than their standard meaning. std is an abbreviation of standard. std is the standard namespace. cout, cin and a lot of other things are defined in it. (This means that one way to call them is by using std::cout and std::cin.
) The keyword using technically means, use this whenever you can. All C standard library types and functions are declared in the std namespace or namespaces nested inside std.using namespace Test using namespace stdNamespace names need to be unique, which means that often they should not be too short. "using" in C is pretty much the same thing as "import" in Java. The analogy does not go all the way C namespaces are more malleable than JavaQ: Convert std::string to std::wstring using std::ctype widen(). What does mean and how do I know if my WebApp does GC too oftenor not. Now, you could have a variable named cout in another namespace other than std without any confliction with the cout variable in the std namespace. Obviously, a constructor cannot be static. A static member means that it is meant to describe something about the class The built in C library routines are kept in the standard namespace. That includes stuff like cout, cin, string, vector, map, etc. Because these tools are used so commonly, its popular to add "using namespace std" at the top of your source code so that you wont have to type the std Using namespaces, we can create two variables or member functions having the same name.This allows organizing the elements of programs into different logical scopes referred to by names. Namespace is a feature added in C and not present in C. Using namespace we can have class,global variables,functions under one name.How to Use Namespaces in C Programming Language include using namespace stdWay 3 : Using declaration: It is a declaration within the current scope. This means it can override names from a using directive. However, if you do not write using namespace std, then you need to fully qualify the names you use from the standard library.
That means std::string instead of string, std::cout instead of cout, and so forth. It means that all entities in the namespace std will be "lifted" into the global namespace, meaning you wont have to use the std:: for them.For instance in C the following 2 code fragments are equivalent C is also a complex and difficult programming language, which is really not meant for dummies. For example, to effectively use the C Standard TemplateThey can be referenced via fully qualified name std::cout and std::endl, or simply as cout and endl with a " using namespace std" statement. When you use using namespace std you are instructing C compiler to use the standard C library. If you dont give this instruction, then you will have to use std::, each time you use a standard C function/entity. std: std namespace ( C standard library , declare ) using namespace std string std::string vector std::vector This is somewhat dangerous because namespaces are meant to be used to avoid name collisions and by writing using namespace you spare some code, but loose this advantage.why is it compulsory to use using namespace std in c language? -1. So the using statement aliases specific things or even everything in the std namespace in the global namespace.You should read up on Namespaces in C for more information on the subject. This is a signature.
Any samples given are not meant to have error checking or show best practices. in the cpp file, we often see include, , using, namespace, STD. These two sentences are used together. The question is, why arent iostream written as iostream.h for programmers who switch from C to C? Answer: prior to the introduction of name space in the meaning of C Standard C places its identifiers in a namespace called std. To use an identifier from the standard namespace, you can use the scope resolution operator :: to indicate that the programmer means the name defined in a particular namespace.can just write cout, cin, endl, etc. as you normally would. std:: means i am going to use this fxn from the std namespace. the using namespace std line is likeAs for standard C, the VC 6.0 compiler isnt the most conforming (not by a long shot), but it has namespacing down (almost, but thats another topic). Some say use using namespace std, other say dont but rather prefix std functions that are to be used with std:: whilst others say use something like thisMost C users are quite happy readingstd::string,std::vector, etc. C has a standard library that contains common functionality you use in building your applications like containers, algorithms, etc.The using namespace statement just means that in the scope it is present, make all the things under the std namespace available without having to prefix std:: before The goal of this line is to tell compiler that we are using std namespace in the program. But what does a namespace mean? Moreover, why namespaces are used in C? A namespace is a container for identifiers. You should not (but can) use. using namespace stdThis absolutely weird thing just happened to me: (Project using C on Visual Studio 2017). Context: Im sorting some information on a .txt file by their number and using 40 binary files (opened by my code) to help me. std is an abbreviation of standard. std is the standard namespace. cout, cin and a lot of other things are defined in it. (This means that one way to call them is by using std::cout and std::cin.) The keyword using technically means, use this whenever you can. If you specify using namespace std then you dont have to put std:: throughout your code. The program will know to look in the std library to findWhen we specify that Namespace std contains all the classes, objects and functions of the standard C library Do we mean all the classes, objects I know, however, that int just adds one to the value of int.Why is std::uniqueptr::reset() always noexcept? Would drawing darts from a "dart quiver" use up your free item interaction? Why didnt they launch the Falcon Heavy to be injected into Mars orbit? Inline namespaces (C 11). In contrast to an ordinary nested namespace, members of an inline namespace are treated as members of the parent namespace.int main() . using namespace Test using namespace std The book "C Coding Standards" by Sutter and Alexandrescu specifically OK what you are doing. There really is no reason not to put " using namespace std" in your cpp file after all your includes, unless you arent using anything from the standard namespace of course. Possible Duplicate: Why is using namespace std considered a bad practice in C? I have done a little research and am looking for something close to the definitive answer on whether or not, as a.STLPORT: What does namespace std mean? 15 Escape Character Backslash ( ): the escape character Special meaning in C Placed before a select group of characters, it tells the compiler to43 Summary A simple C program containing declaration statements has the format: include using namespace std int main() declaration Without using namespace std when you write for example cout << youd have to put std::cout << Heres a small example for you: without using namespace std include int main() std::cout << "HelloI think it doest means for turbo c!!!!its useing for compiler like visual c!! C does resolution by name, not by signature. That means that if two functions/variables/member variables in the same scope have the same name, they can conflict. When you do something like using namespace std, you are including the entire std namespace in your code. Conditional execution statements. Iteration statements (loops). Jump statements. Functions. Function declaration. Lambda function declaration. inline specifier. Exception specifications (deprecated). noexcept specifier (C11). Exceptions. Namespaces. Types. Specifiers. Storage duration specifiers. In C/C, standard library set elements are included by including the statement " using namespace std" i.e. it signifies, well be using all standard elements in our code. The meaning of each word is there in the above answers. We can also write using std When you use using namespace std you are instructing C compiler to use the standard C library. If you dont give this instruction, then you will have to use std::, each time you use a standard C function/entity. However, C allows operators to be overloaded. When you overload an operator, you give it a new meaning when that operator is used with an object of a particular type.using namespace std Why we use namespace std in C courseno - Duration: 4:22.Advanced C: Namespace and Keyword "using" - Duration: 6:32. Bo Qian 12,077 views. Have you ever wondered why do we put using namespace std on the top of our code in C.The std namespace is special, The built in C library routines are kept in the standard namespace. That includes stuff like cout, cin, string, vector, map, etc. However, if you do not write using namespace std, then you need to fully qualify the names you use from the standard library. That means std::string instead of string, std::cout instead of cout, and so forth. Why a constructor can not be static and virtual? Why objects with a constructor or destructor can not be used as a member of union? Please answer if you know ans of any of these questions. In c ,what is meaning of " using namespace std" directive? I need a solution. Go Premium. C. std.With using namespace a namespace can be made available in the current namespace, this means all functions/objects from such a namespace can be used in the current namespace too. I am certain if I was not trying slef-teaching C, that this question would have been answer before. What is the use of using namespace stdThe using std::cout part tells C to assume that wherever you say cout , you really mean std::cout . Dont use C coding standards (even if slightly modified for C) and dont use ten-year-old C coding standards (even if good for their time).Probably not. People dont like typing std:: over and over, and they discover that using namespace std lets the compiler see any std name, even if unqualified. Was looking over some code and the repetition of std::cout instead of using using namespace std caught my attention as why all these extra keystrokes to type stdBut in C using namespace X means to bring everything in that namespace into the global namespace in the current scope. The std namespace. When C was originally designed, all of the identifiers in the C standard library (such as cin and cout) were available to be used directly. However, this meant that any identifier in the standard library could potentially conflict with a name you picked for your own identifiers. Having a local variable called count means that using namespace std wont enable you to use count instead of std::count.std::string vs string in c. As the other answer already stated, using std:: is necessary unless you import either the whole std namespace or std::string (see below). So, it is that iostream itself is there in namespace std? What is the meaning of both the statements with respect to using cout?Is requiring a certain order for includes in c a sign of bad library/header design? C namespaces: cross-usage.