HP 33s - Manual (Page 100)

6–8 Entering and Evaluating Equations
To edit an equation you're typing:
1. Press b repeatedly until you delete the unwanted number or function.
If you're typing a decimal number and the "_" digit–entry cursor is on, b
deletes only the rightmost character. If you delete all characters in the number,
the calculator switches back to the "¾" equation–entry cursor.
If the "¾" equation–entry cursor is on, pressing b deletes the entire rightmost
number or function.
2. Retype the rest of the equation.
3. Press ‘ (or ‡ ) to save the equation in the equation list.
To edit a saved equation:
1. Display the desired equation. (See "Displaying and Selecting Equations"
above.)
2. Press b (once only) to start editing the equation. The "¾" equation–entry
cursor appears at the end of the equation. Nothing is deleted from the
equation.
3. Use b to edit the equation as described above.
4. Press ‘ (or ‡ ) to save the edited equation in the equation list,
replacing the previous version.
To clear an equation you're typing:
Press { c then press {&}. The display goes back to the previous entry in
the equation list.
To clear a saved equation:
1. Display the desired equation. (See "Displaying and Selecting Equations"
above.)
2. Press { c . The display shows the previous entry in the equation list.
To clear all equations, clear them one at a time: scroll through the equation list until
you come to    ! ! , press
™ , then press { c repeatedly as
each equation is displayed until you see    ! ! .
Example: Editing an Equation.
Remove 25 in the equation from the previous example.