`cl'
    String of commands to clear the entire screen and position the cursor 
    at the upper left corner. 
`cd'
    String of commands to clear the line the cursor is on, 
    and all the lines below it, down to the bottom of the screen. 
    This command string should be used only with the cursor in column zero.
`ce'
    String of commands to clear from the cursor to the end of the current line. 
`cm'
    String of commands to position the cursor at line l, column c. 
    Both parameters are origin-zero, and are defined relative to the screen, 
    not relative to display memory.
`co'
    Numeric value, the width of the screen in character positions.
`li'
    Numeric value, the height of the screen in lines.