屏幕窗口程序 　　在屏幕上开出三个窗口，它们的行列坐标如下图所示：　　光标首先定位在右窗口最下面一行的行首（15，50），如果从键盘输入字符，则显示在右窗口，同时也显示在下窗口的最下面一行。若需要将字符显示于左窗口，则先按下<-接着再从键盘输入字符，字符就会从左窗口的最下行开始显示，同时下窗口也显示出左窗口的内容。如若再按下-〉键，输入的字符就会接在先前输入的字符后面显示出来。当一行字符显示满后，窗口自动向上卷动一行，输入字符继续显示于最低一行。

　　编写屏幕窗口程序时，要求将一些功能程序段定义成宏指令：

scroll:向上卷动

clear:清屏

get-char：接收输入字符

Display：在屏幕上显示字符

pos-curse：光标定位-Screen window procedure cursor positioning in the right window, the first line the bottom line of the first (15.50), if the characters from the keyboard is displayed in the right window, but also shows the next window, the bottom line. If you need the character shown in the left window, then press the <- and then re-enter the characters from the keyboard, the characters will start from the left window shows the most down, while the left under the window also shows the contents of the window. Should the re-press-> button, enter the character will then enter the characters in the back of previously displayed. When the line character display is full, the window automatically scroll line up, enter the characters continue to show the minimum line.

The preparation of the screen window program, requested that the segment of some function defined as macros:

scroll: Scroll

clear: clear screen

get-char: to receive input characters

Display: display characters on the screen

pos-c