;This is an example of using PROCs.›;›;The program draws a border around›;the screen and plots a '*' and›;makes it move randomly.›;›;I hope by explaining it near the›;line where the command helps.››››;This PROC erases the old '*' and›;plots a new '*' in a new position.›;Notice how the parameters are used.››;The Position command works the same›;as it does in BASIC.  It just places›;the cursor at the place on the›;screen when the next character will›;be printed.›››PROC move(BYTE oldx,oldy,newx,newy)››    ›  Position(oldx,oldy)›  Print(" ")›  Position(newx,newy)›  Print("*")› ›RETURN››››PROC draw_screen(BYTE x,y)››;Here we draw the border and place›;the '*' at starting position x,y›;›;The 'Put(125)' simply clears the›;screen.›››  BYTE i››  Put(125)›  PrintE("+-----------------------------------+")›  FOR i=1 TO 21›  DO›    PrintE("|                                   |")›  OD›  PrintE("+-----------------------------------+")›  Position(x,y)›  Print("*")›››RETURN››PROC main()››;Here's the meat of the program.›;It will be explained as we get to ›;each line.›››  BYTE x_rnum,›       y_rnum,›       old_xpos,›       old_ypos,›       new_xpos,›       new_ypos››  CARD delay››  Poke(752,1) ;this turns off the cursor›              ;Try deleting this line›              ;to see what happens››››;here we set the starting position of›;the '*' and draw the screen.  Notice›;how the paramters are sent›› ›  new_xpos=28›  new_ypos=10›  draw_screen(new_xpos,new_ypos)›››  DO  ›;an infinite loop.  You must press›;RESET to exit.›››    x_rnum=Rand(2)›    y_rnum=Rand(2)››;get a random number from 0 to 1›;a 1 means move right or down›;a 0 means move left or up›››    old_xpos=new_xpos›;so we can erase the old '*'››    IF x_rnum=1 THEN       ;move right?›      new_xpos==+1         ;yes, increase the x position›      IF new_xpos>36 THEN  ;are we out of range?›        new_xpos=3         ;Yes, position '*' on the left›     FI›    ELSE                   ;x_rnum was a 0 so›      new_xpos==-1         ;we move left›      IF new_xpos<3 THEN   ;are we out of range?›        new_xpos=36        ;yes, move '*' to the right›      FI›    FI›    ›    old_ypos=new_ypos›;also so we can erase the old '*'›  ›    IF y_rnum=1 THEN       ;should we move down?›      new_ypos==+1         ;yes›      IF new_ypos>21 THEN  ;too far down?›        new_ypos=2         ;reset to top of screen›      FI›    ELSE›      new_ypos==-1         ;no, we have to move up›      IF new_ypos<1 THEN   ;can't above the top of the screen›        new_ypos=21        ;move to the bottom›      FI›    FI›   ››;here's where we move the '*'›;we send it old_xpos and old_ypos so›;the old '*' can be erased.››    move(old_xpos, old_ypos, new_xpos, new_ypos)›››;here we just delay the program by›;giving it something useless to do›;for a while. Like counting from 1›;to 3000.  You can delete these lines›;to see how fast it runs without›;the delay››    FOR delay=1 TO 3000›    DO›    OD› ›  OD   ;end of the infinite loop›       ;RESET to end››RETURN››