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* Hello world! program
* Preprocessing command
* Header file
* Principal function
* Function return value
* notes
* Hello world! Enhanced Edition
<> One , The simplest C program Hello world!
#include<stdio.h> // Compile preprocessing command int main() // Defining the main function , The main function type is integer （int） { // Flag for the start of the function printf
("Hello world!"); // Output content return 0; // Returns an integer value when the function completes execution 0 } // Flag for the end of the function
Operation results ：
<> Two , preprocessor directives （#include<stdio.h>）
1. Action bar stdio.h The contents of the header file are read in
2. Other preprocessing commands ：#define
<> Three , Header file （stdio.h）
stdio.h There are inputs in the file （scanf）, output （printf） Prototype declaration of equal function
* std Representation standard ：standard
* i Represents input ： input
* o Represents the output ：output
* .h Represents the header file head （ File suffix ）
<> Four , Principal function （main）
every last C All language programs must have one main, And the main function has and only has 1 individual .
<> Five , The return value of the function （return 0）
Principal function main The return value of is 0 Indicates that the program exits normally
When the return value is nonzero , Indicates that the program exited abnormally
<> Six , notes
C The language allows two annotations
The first one ： with // Starting single line comment
The second kind ： with /* start , with */ Closing multiline comment （ Block annotation ）
<> Seven ,Hello world! Enhanced Edition
Enhanced Edition 1………………
#include<stdio.h> int main() { printf("\tHello world!\n"); // \n Line break \t Horizontal space
return 0; }
results of enforcement ：
Enhanced Edition 2………………
#include<stdio.h> int main() { printf("\n\tHello\n\nworld!\n"); // \n Line break \t
Horizontal space return 0; }
results of enforcement ：
Enhanced Edition 3…………… Welcome to C The world of language
#include<stdio.h> int main() { printf("\n\t***********************\n"); printf(
"\t* *\n"); printf("\t* Welcome to C The world of language *\n"); printf("\t* *\n"); printf(
"\t***********************\n"); return 0; }
results of enforcement ：
adopt \n Line break ,\t The combination and design of some escape characters such as horizontal space , A program that allows you to write , The output content is more beautiful and attractive .
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That's what I've been doing over time C Language learning , The simplest summary C The function of various contents in the program and the enhanced version Hello world!
If there is anything wrong with the above , Please correct me （ Common progress ）
This is the first one I wrote C program , I don't know if you are !!!
At that time , While writing this program , On the computer , Repeated revision , Finally, when output on the screen Hello world! When the heart suddenly exclaimed ： From then on, it can be regarded as a program ape “ No return ”
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