//p01.c   --- using variable 使用變數
//@CopyLeft by tsaiwn@csie.nctu.edu.tw
//
#include <stdio.h>
#include <math.h>
double x;  //  (注意 1) 變數 variable;  // C++ 式的註解 comment
int main( ) {   // 大多數 main program 都這樣開頭
     printf("Give me x: ");
     scanf("%lf", &x); 
     printf(" sqrt 根號 %f =%f\n ", x,   sqrt(x) );
     printf("Bye bye!\n");
     return  0;    //   告知作業系統(OS)表示我們這主程式正常結束
} // main(
/******  Running Script
D:\test> path C:\TC\BIN;%path%

D:\test> path C:\Dev-Cpp\bin;%path%

D:\test> gcc p01.c
Give me x: 5
 sqrt 根號 5.000000 =2.236068
 Bye bye!

D:\test> a
Give me x: 3
 sqrt 根號 3.000000 =1.732051
 Bye bye!

D:\test> a
Give me x: 9
 sqrt 根號 9.000000 =3.000000
 Bye bye!

D:\test>
D:\test> a.exe
Give me x: 2
 sqrt 根號 2.000000 =1.414214
 Bye bye!

D:\test> tcc p01.c

Turbo C++ Version 3.00 Copyright (c) 1992 Borland International
p01.c:
Turbo Link  Version 5.0 Copyright (c) 1992 Borland International

        Available memory 4106928

D:\test> p01.exe
Give me x: 2
 sqrt 根號 2.000000 =1.414214
 Bye bye!

D:\test> p01
Give me x: 9
 sqrt 根號 9.000000 =3.000000
 Bye bye!

D:\test>
**************************************/