Compiling a Simple C Program

The classic example program for the C language is:

#include <stdio.h>

int main(void)
{
printf("hello world!\n");
 return 0;
}

To compile the file with gcc,use the following command:

gcc -Wall hello.c -o hello

Example1

1. 建立文件vim hello.c，键入C源码
2. 编译文件gcc -Wall hello.c -o hello（指定编译文件名为hello，默认为a.out）
3. 执行文件./hello

exp1

Compiling Multiple Source Files

• A program can be split up into multiple（许多个） files.This makes it easier to edit and understand,especially in the case of large programs.
• The difference between the two froms of the include statement #include "FILE.h" and #include <FILE.h> is:
  -- #include "FILE.h" searches for "FILE.h" in the current directory before looking in the system header file directories.
  -- #include <FILE.h> searches the system header files,but does not look in the current directory by default.

Example2

1. 建立文件vim hello.h

void hello(const char* string);

2. 建立文件vim hello.c

#include <stdio.h>
#include "hello.h"

void hello(const char* string)
{
printf(string);
}

3. 建立文件vim main.c

#include <stdio.h>
#include "hello.h"

int main(void)
{
hello("hello world!");
return 0;
}

4. 编译文件gcc -Wall hello.c main.c -o newhello
5. 执行文件./newhello

exp2

2020.10.8