在计算机屏幕显示Hello World!、函数求和、判断正负数、一个具有两个数加减乘除功能的计算器、用while循环求1+2+3+...+10的和(On the computer screen, the Hello World!, the function summing, the positive negative, a calculator with two numbers, subtraction and multiplication, and the while loop for 1+2+3+... +10)