The new HP-97 Fully Programmable Printing Calculator. Published: The Straits Times, 25 June 1977, Page 17

HP-97 was code-named “Kitty Hawk” with large keys and a bright LED (light-emitting diode) display. These features, combined with the ease of saving programs and data on magnetic cards (which themselves were interchangeable with the HP-67 models), made this a popular product for business and technical users.

HP Calculator Heritage HP 27 - 1976 The HP 27 was a handheld scientific LED display calculator introduced in 1976. This advertisement appeared in the June 1976 issue of Popular Electronics. Caption: Is our new HP-27 an engineering work of art? Or simply the most powerful preprogrammed calculator we’ve ever built? Hewlett-Packard Company - Corvallis Division

The new HP-67 Fully-Programmable Pocket Calculator. Published: The Straits Times, 1 October 1976, Page 27

The New HP-97 The new HP-97 Fully-Programmable Printing Calculator. Published: The Straits Times, 30 September 1976, Page 31

Wide range of capability Hewlett-Packard introduced its first desktop programmable calculator in 1968 and the world’s first pocket scientific calculator in 1972. Since then, Hewlett-Packard has introduced several desk-top and pocket calculators with technologically advanced features, each with different capabilities for different levels of problem sophistication. To properly select a calculator, you must consider the problems you’re facing today, as well as the problems you’re likely to face tomorrow. Pocket calculators For example, if your main concern is general math - addition, subtraction, multiplication, and division - with an occasional need for log or trig functions, the HP-21 may be just perfect for you.

The HP-21 is a full-function scientific pocket calculator that offers features and functions not available on apparently similar models. Most important of these is HP’s remarkably efficient RPN logic system which gives you the problem-solving power of an ’equals’ key and at least three levels of parentheses. Yet, this ingenious system is distinguished by its similarity to your natural way of solving mathematical problems. It allows you to approach the solution of every problem in the same natural manner as you would with a slide-rule, through the process of equation simplification.

HP-25 Scientific Programmable Pocket Calculator Specifications Pre-programmed functions Trigonometric (all in decimal degrees, radians, or grads): Sin x: Arc Sin x: Cos x: Arc Cos x: Tan x; Arc Tan x. Logarithmic: Log x: Ln x; e5; 10^x. Statistical: mean and standard deviation. Other: conversions between decimal hours, degrees, radians, or grads and hours (degrees)/minutes/ seconds: rectangular/polar coordinate conversions, integer/fraction truncation: absolute value; full register arithmetic. Programming features 49-step program memory; conditional branching based on any of eight relational tests (x<0,=’’>_0, x#0, x = 0): direct branching: ability to review or execute programs step-by-step: ability to add or modify program steps; PAUSE and NO-OPERATION program instructions.