HP 48GX locked in ALG PRG

[Brooke]

Hi: My HP 48GX is displaying '(Pi symbol)' on the bottom line and 5 on the line above.
At the very top right corner of the display is shows ALG PRG.

I don't know how I got into this mode but can not get out of it.
Pressing blue/shift MODES sounds a beep but otherwise does not change the screen.
The left softkey label is ECHO and all the others are blank.

Is there a way to reset factory defaults?
Have Fun,
Brooke