C The definition of the header file is parsed

A complete program consists of three parts: program number, program content, and program end.

1. Header file: The header file contains the library functions to be called in the program (e.g., printf, scanf, etc.) and is included in the header. SIN, TAN, SQRT, and other functions used in mathematical calculations are included in the header file.

When calling a library function in a program, include or include "header filename" must be written at the beginning of the program.

2.Main function: the main part of the program, the main part of the algorithm.

3.Subfunction: The method used in the main function. In order to avoid errors caused by the length of the main function, a certain process in the algorithm will be picked out and implemented with a subfunction. Subfunctions are called in the main function and defined outside of the main function.

4.struct: Optional, is a special type of data that is defined by the programmer as needed.

Header files are meant to be included, and they can be contained by multiple source files. Include is equivalent to inserting the contents of a header file into the source file.

A function declaration can be multiple times, and a definition can only be made once.

Definitions can only be made once, while there is no limit to the number of declarations. Any identifier must have at least a declaration before it can be used, and by placing the declaration in the header file, you can include the header file whenever you need to use the identifier. If you put the definition in the header file, the identifier is defined every time the header file is included, which is easy to have problems when compiling and connecting multiple files.

Inclusion is equivalent to adding the contents of the included file to it, and is no different from replacing the corresponding inclusion statement with the content of the included file. The advantage of using header files is that you don't have to worry about duplication of effort.

Anyway, in the end, the compiler compiles the contents of the included files by merging them together. So, does lz think there is a difference between calling a runtime call and calling any function?

The first question, in a nutshell, is the new standard and the old standard is the same as iostream, and iostream is recommended. 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.

About whether to bring or not. H Question:

No. H is a new set of function standard libraries provided by C++ later, but in order to be compatible with previous programs, so it is bringed. H's is still available. This is also the case with the original C libraries (e.g. C is now Cstdio in C++).

You can use both, but you don't need it. h, you need to use the namespace std.

If you can't find one or the other, use the other

The new C++ library should contain header files.

#include

using namespace std；

The include you said contains the old libraries.

Standard mode is recommended.

include is a standard C++ usage, which is not in the standard C++ header. h

Yes. h is the header file for C.

Each C++ C program is usually divided into two files. A file that holds the declaration of a program, called a header file. The other file is used to hold the implementation of the program, called the definition file.

The header file of the C++ C program starts with "h" and the definition file of the C program starts with ".c" as the suffix, and the definition file of a C++ program usually starts with ".

cpp" (there are also some systems that end with ".).cc" or".cxx" as a suffix).

Create Method: File New Select the file bar in the pop-up box C++ C Header File OK, and then start to write the header file content.

Header file role:

1. The header file can define the list of functions used, which is convenient to check the functions you can call;

2. The header file can define a lot of macro definitions, that is, the definition of some global static variables, in this case, as long as the content of the header file is modified, the program can make corresponding modifications, without having to run to the cumbersome ** to search.

3. The header file is just a declaration, does not occupy memory space, to know its execution process, it depends on which function you declare in the header file. c file, only to know.

4. He doesn't come with it, so he doesn't need it.

5. If you want to count a number to the nth power, you have to call the pow() function, and this function is defined in it, to use this function, you must call this header file.

Once the header file is written, start with the "file name." h" format! When called in the main program, the format is: include filename. h>

As with writing a generic CPP file, in general, user-written header files have a name extension. h (while the C++ standard header file does not have an extension), the header file is generally the definition of some functions and classes (not definitions) and some very few functions (inline functions), to use the written header file just include it.

To give you an example of a header file, ifndef rijndael alg h

#define __rijndael_alg_h#define maxkc (256/32)

#define maxrounds 14typedef unsigned char word8;

typedef unsigned short word16;

typedef unsigned int word32;int rijndaelkeysched (word8 k[maxkc][4], int keybits,word8 rk[maxrounds+1][4][4]);

int rijndaelkeyenctodec (int keybits, word8 w[maxrounds+1][4][4]);

int rijndaelencrypt (word8 a[16], word8 b[16],word8 rk[maxrounds+1][4][4]);

int rijndaelencryptround (word8 a[4][4],word8 rk[maxrounds+1][4][4], int rounds);

int rijndaeldecrypt (word8 a[16], word8 b[16],word8 rk[maxrounds+1][4][4]);

int rijndaeldecryptround (word8 a[4][4],word8 rk[maxrounds+1][4][4], int rounds);endif is in the main program, you need to include this header file first, and then you can call the contents inside.

1. Install a plug-in, click on the function name to go to the header file and definition, but some functions are not open source, and you can only see the declaration.

Appearance. 2. A function is a program that is together and can do a certain thing. Also called subroutines, (in OOP) methods.

A larger program should generally be divided into several blocks, each of which is used to implement a specific function. All high-level languages have the concept of subroutines, and subroutines are used to implement the functions of modules. In C, the role of a subroutine is made up of a main function and several functions.

Other functions are called by the main function, and other functions can also be called to each other. The same function can be called by one or more functions as many times as it wants.

3. The C language came out in the early 70s. In 1978, the C language was officially published by Bell Labs, the American Telegraph Company (AT&T). At the same time, he co-authored the famous book "The C Programming Language".

It is often referred to simply as "K&R", and some people call it the "K&R" standard. However, there was no complete standard C language defined in K&R, and a C language standard was later developed by the American National Standards Institute and published in 1983. It is commonly referred to as ANSI C.

Windows search files are generally installed compiler, which can be found in the include folder of the compiler, but the ** of the windows api cannot be seen Encapsulated.

I don't know what device you're using, but if the function is written, you can right-click to go to the definition or declaration, and you should be able to view the annotation; If it's the device that comes with it, just go down to MSDN.

Just install MSDN and put it in the same folder as C++! It seems to have 2g.