HP 33s - Manual (Page 22)

1–6 Getting Started
Keys for Clearing (continued)
Key Description
{c The CLEAR menu ({º} {# } {} {´})
Contains options for clearing x (the number in the X–register), all
variables, all of memory, or all statistical data.
If you select {}, a new menu ( @ {&} {}) is
displayed so you can verify your decision before erasing
everything in memory.
During program entry, {} is replaced by { }. If you select
{ }, a new menu (  @ {&} {} ) is displayed, so you
can verify your decision before erasing all your programs.
During equation entry (either keyboard equations or equations in
program lines), the   @ {&} {} menu is displayed, so you
can verify your decision before erasing the equation.
If you are viewing a completed equation, the equation is deleted
with no verification.