by Thomas A Hender
Objective design a shirt-pocket calculator package for minimum factory cost, with reliability equal to or better than that of the HP-35 family. HP quality standards must be maintained. Shirt-pocket size was achieved by reducing the number of keys from 35 to 30 one less horizontal row and by spacing the keys closer together. Spacing is the minimum deemed comfortable for the majority of users. Also, the display was reduced from 15 to 12 digits, and decimal points share positions with their...
by Randall B Neff and Lynn Tillman
IN 1972, HEWLETT-PACKARD INTRODUCED the HP-35 pocket scientific calculator,1 the first in a family of calculators that eventually grew to include six members, from the original HP-35 to the sophisticated fully programmable HP-65.2 Now there is a second generation of HP pocket calculators. Currently this new calculator family has three members, designated HP-21, HP-22, and HP-25. The HP-21 Fig. 1 is a basic scientific calculator that replaces the HP-35, the HP-22 Fig. 2 is a business calculator,...
An Example of HP Programming
A simple ecological model of interacting populations consists of rabbits with an infinite food supply and foxes that prey on them. The system can be approximated by a pair of nonlinear, first-order differential equations change in rabbits with time change in foxes with time where r is the number of rabbits, f is the number of foxes, and a is a positive constant to show how frequently rabbits and foxes meet. When a 0 there are no encounters the rabbits keep breeding and the foxes starve. For a...