|An HP Catalog described HP-67 as "A major leap forward in fully-programmable personal calculators. These are the most powerful personal calculators Hewlett-Packard has ever made." (Personal Calculator distinguished them from high-end calculators like the HP-9825 and "mid-range" models like the HP 9815.)|
The HP-67 packed so many functions on to a small keyboard that three shift keys were needed. The HP-97's larger keyboard needed just one shift. The HP-97 added the same printer introduced in the HP-91. This battery powered printer could print the display, the stack, data registers and programs. Programs were printed with step numbers, keycodes and key mnemonics. It could also be used in trace mode to debug programs.
Indirect Addressing was a particularly important addition giving the calculators, true computer power. Once a value was stored in the indirect register via STO I, it could be used to control store and recall addresses, goto and gosub addresses, format the display, and select a loop counter by using (i) as the argument.