Directives are special commands that do NOT use a semicolon.

!clear               Clear input from a mistake. This erases the active memory back to the last prompt (>). However, it does not erase the display.

!credits            Display the credits and copyright information.

!include           Execute an external ISETLW file. Example:  !include discrete.stl

!memory         Display or increase ISETLW memory partition. !memory will show the current memory allotment.
Example: !memory 500000 will increase this to 500K.

!rational          This is used to work with rational fractions instead of decimal representations. Setting !rational on will allow the calculation 5/4 + 3/8; to give the answer 13/8. Using !rational off to go back to decimal representation will cause 5/4 + 3/8; to give 1.625.

!setrandom     This controls whether sets are displayed in order or randomly. The default is !setrandom on. In this situation, the elements of a set can appear in any order.  Using !setrandom off will cause the command {1..9}; to produce {1, 2, 3, 4, 5, 6, 7, 8, 9}.