What does include iostream mean

include means to introduce the iostream library, that is, the input and output stream library.

The basis of the Ostream library is two types named iStream and OStream, which represent input and output streams, respectively. A stream is a sequence of characters to be read or written from an IO device. The term "stream" attempts to state that characters are generated or consumed in chronological order.

The standard library defines 4 IO objects. Input is processed using an istream type object named Cin (pronounced see-in). This object is also known as the standard input.

The output is processed using an ostream type object named Cout (pronounced see-out), which is also known as standard output.

The standard library also defines two other Ostream objects, named CER and CLOG (pronounced "see-err" and "see-log", respectively). The cerr object, also known as a standard error, is usually used to output warnings and error messages to the user of the program. Whereas, the clog object is used to generate general information about the execution of the program.

iostream history:

Many people who study C++ know that there is one in C++. This was used in earlier versions of C++ and is no longer supported today.

The current version uses iostream. （#include "iostream"After the early version of C++ came out, the industry generally reported that it was slow, and C++ was constantly improving, and in one version, a new input and output stream was written, which was faster and generally accepted by the industry.

In order to highlight the differences between C++ and C, as well as C++'s progress over the past, as well as its compatibility with earlier C++ languages, the C++ standard named this input and output stream IOSeek, but also retained, and the two files can be seen in the external dependencies in the Viual Studio. Their ** are not the same.

Ingest header files.

The purpose of this header file is to contain methods for manipulating input and output streams, such as reading a file and reading it as a stream.

Contains the standard IOstream header file of C++, that is, the compiler first copies all the content in the 100-header file iostream to the include position, and then compiles it.

An instance of a class template

iostream（.h)that the library integrates two sets of standard instances of the entire iostream class template hierarchy: one is single-byte-oriented and handles char-type elements; The other group is broadbyte-oriented and handles elements of type wchar t.

An instance targeting a single byte (char) might be iostream(.).h) a better known part of the library.

Classes such as ios, istream, and ofstream are all single-byte oriented. The image on the right shows the names and relationships of all classes for a single byte.

The above content refers to: Encyclopedia.

include contains the meaning, the following iostream is a header file, used to tell the compiler some methods you use, where the class is, if you don't write this will report the error xx can't be found.

The standard IOstream header file containing C++ is that the compiler first copies everything in the header iostream to the include position, and then compiles it.

Note that the name of this standard I/O header file in C++ is iostream, no. h suffix.

This is not the case with C's standard I/O header file.

":: Indicates the scope and affiliation in C++. ": is the highest level of operators, and it is divided into three types, which are as follows:

1. Scope Symbol:

The scope symbol ":: is generally preceded by the class name, followed by the member name of the class, C++ as an example to avoid different classes having members with the same name and using the scope to distinguish them.

For example, a and b represent two classes, both of which have members.

Then: 1, a::member represents the member in class A.

2. b::member represents the member in class b.

2. Global Scope Symbol:

Global Scope Symbol: When a global variable has the same name as one of the variables in a local function, then it can be distinguished by :, for example:

3. Scope Decomposition Operator:

is the scope decomposition operator in C++, "For example, if a class A is declared, and a member function voidf() is declared in class A, but the definition of f is not given in the class declaration, then when defining f outside the class, it should be written as voida::f(), indicating that this f() function is a member function of class A."

Include is used in the old standard C++. In the new standard, the term is used to mean an input and output stream. include is the standard C++ header that any standards-compliant C++ development environment has.

Also note: add when programming in the VC:

using namespace std;

The reason for this is: the suffix is. H's header file C++ standard has been clearly stated that it is not supported, and earlier implementations defined the standard library function in the global space and declared it in the band.

In the header file with the H suffix, the C++ standard stipulates that the header file does not use the suffix in order to distinguish it from C and to use the namespace correctly. h。Therefore, when used, it is equivalent to calling a library function in C, using the global namespace, which is the early C++ implementation; When used, the header file does not have a global namespace defined, and must use namespace std; This is how cout can be used correctly.

Relationship. is the old C header file, which corresponds to the char*-based string handling function; is a C++ header file wrapped with std, corresponding to the new string class; is the STD version corresponding to the old C-header file. The relationship between and, similar to the relationship of and, implements the same function, mainly the difference between whether to use the namespace std or not.

A namespace is a namespace, which is to stuff some names into a space and give another name to avoid the same name. For example, if I have another class called string, and you also have a class called string, then putting it together will compile an error, but if I put it in namespace my, and yours in namespace your, then there will be no conflict, but when I use it, I must use my::string to represent my string, your::

string represents your string.

You can also do without using namespace std; Instead, use using std::string. In this way, you can also use string directly.

This is not the same thing as include, and include ensures that your ** contains the string declaration. You're useless using namespace std; It's just not the proper use of its name.

include is the general name of the header file, and iostream header file (stream input and output) iostream is a single header file, not a string can be replaced.

CIN >> (stream input).

cout<< (stream output).

if() (if, then).

else

for() (loop statement).

int (defines the variable as an integer (integer)).

long long (defines the variable as a long integer).

float (defines the variable as a single-precision floating-point number (single-precision real number)), double(defines the variable as a double-precision floating-point number (double-precision real number)), and so on.

IOSTREAM means input and output streams. include is the standard C++ header that any standards-compliant C++ development environment has. Also note: add when vs programming:

using namespace std;

The reason for this is: the suffix is. H's header file C++ standard has been clearly stated that it is not supported, and earlier implementations defined the standard library function in the global space and declared it in the band.

In the header file with the H suffix, the C++ standard stipulates that the header file does not use the suffix in order to distinguish it from C and to use the namespace correctly. h。Therefore, when used, it is equivalent to calling a library function in C, using the global namespace, which is the early C++ implementation; When used, the header file does not have a global namespace defined, and must use namespace std; This is how cout can be used correctly.

The string class you're using is inherited from .

is just an input and output stream, which is a bit different from C.

"#include"This means: the programming language of the C system, the declaration is inserted in this place in other files. include is generally used in the compilation environment of C, C++ and other languages (that is, in the programming of programming software), to put it bluntly, it means that a bunch of ** is to be inserted in this place, and this pile ** is in another file.

A language is a general-purpose computer programming language that is widely used. C is designed to provide a programming language that can compile in a simple way, handle low-level memory, generate a small amount of machine code, and run without any runtime support.

2.Although C provides many low-level processing functions, it still maintains a good cross-platform characteristic, and C programs written in a standard specification can be compiled on many computer platforms, including some embedded processors (microcontrollers or MCUs) and supercomputers.

It is to include the library file, which defines the input and output stream objects such as cin and cout. Once included, you will be able to use these objects.

Literally: Contains header files, .,h ends with a header file.

This is the header file required by the C++ program, which contains the definition of the input and output streams of the C++ program, if this header file is not included, the Cout<< and Cin >> in the C++ program will be compiled with an error.

and are different in terms of interface and execution.

The components are declared in the form of an STL, but the components are declared as global.

You can't confuse these two libraries in one program. As a habit, it is generally used in the new **, but if you are dealing with the ** written in the past, you can continue to use the old ** to maintain the consistency of the ** for the sake of inheritance.

It means that you are using a namespace, that is, there should be a sentence at the beginning of the program using namespace std;

This follows the C++ standard.

It does not follow the C++ standard and is not recommended.

This is a C standard library and is not recommended for C++.

include with cin and cout

include is the standard library for c, with scanf and printf