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The Casio PB-500F is closest to the FX-750PF because of its two locations for RC module and 16 KB of maximum RAM available.
Yet, like every PB it hasn't the F key for rapid access to functions.
Like for all models followed by the letter F, the access doors to the Ram cards are in the back - and not on the edge of the machine under the keyboard.
As for the fx-750p and fx-750Pf, a SHIFT key allows access to BASIC functions written in red above the keys.
On the FX-750pF, SHIFT+figures give acces to Physic constants.
In Katakana mode, the SHIFT key provides access to special characters written in red under certain keys.
These characters are part of EXT mode on PB-100. They are missing on fx-750p keyboard.
The F keys Katakana Keys are not at the same place on the hull and, each machine has certainly both circuits. Only the hulls change.