TABSTEP (System Variable)

is a read-write integer system variable which determines how the  key works. It contains a value between 0 and 16, inclusive.

When the  button is pressed, the cursor moves to a column which is the next multiple of   columns from the left-hand side (unless there is no such column, in which case the cursor will be at the end of the line, but the next character that gets printed will be at the very left of the next line down, with the screen scrolling up if necessary). In particular, if  is 0, the   key essentially does nothing.

When assigning a value to, the value is rounded down if it is not an integer, then changed to 0 if it is negative or changed to 16 if it is greater than 16.