ENG display mode on HP-15C

[Steve Simpkin]

Interestingly enough, the first HP model to incorporate the ENG display option, the HP-25, always displayed at least 3 significant digits of the value. For example, when set to ENG 0, the value (100 * PI) is shown as 314 E0. All other models after the HP-25 that have the ENG display option show 300 E0.

From the HP-25 User's Handbook:
"Engineering notation is selected by pressing f [ENG] followed by a number key. In engineering notation, the first three digits are always present, and the number key specifies the number of additional digits displayed after the first three."

From the HP-29C/19C User's Handbook:
"Engineering notation is selected by pressing f [ENG] followed by a number key. The first significant digit is always present in the display, and the number key specifies the number of additional significant digits to which the display is rounded."

It seems HP had a change of heart after the HP-25.