Book  Hewlett packard StepbyStep Solutions For Your HP
Calculator: Calculus (English), 2.6.1988, 95 pages 
Contents 
Function Operations, Differential Calculus,
Integral Calculus 
Comment  Bound printout from MoHPC CDROMs 
Book 
Hewlett packard StepbyStep Solutions For Your
HP Calculator: Probability and Statistics (English), 1.11.1987, 77 pages 
Contents 
Statistics Matrix Setup, Basic Statistics for
Multiple Variables, Regression, Test Statistics and Confidence
Intervals, Combinations and Permutations 
Comment 
Bound printout from MoHPC CDROMs 
Book 
Hewlett packard StepbyStep Solutions For Your
HP Calculator: Vectors and Matrices (English), 3.6.1989, 108 pages 
Contents 
General Matrix Operations, Systems of Linear
Equations, Vector Spaces, Eigenvalues, Least Squares, Markov Chains, A
Sample Appliaction 
Comment 
Bound printout from MoHPC CDROMs 
HP codename, series  Paladin (HP28C), Orlando (HP28S), Champion/Clamshell 
Type, Precision, Input Mode  Scientific, 12 BCD digits, exponent ±499, Reverse Polish Notation 
Programmable  Yes, in RPL
(Reverse Polish Lisp) with arbitrary program and variable names. In
fact, a program is treated as a variable containing program code (other
variable types are strings, numbers, vectors, matrices, lists). It turns out that the HP28S is a surprisingly fast unit! It easily beats the Casio fx880P, Casio fx2000C, TI74 and the HP32SII. Compared to the HP15C/41CV/CX it is about 20 times as fast. Only the HP48GX/HP49G are significantly faster. The RPL programming model is similar to the HP48GX and HP49G. 
Performance Index  HP28S: 54 
Memory  HP28C: 2048 bytes, HP28S: 32kByte All variables, programs and the (infinite) stack are stored in this permanent memory. 
Display  138x32 pixel black&white LCD, 23x4 characters 
Special features  Folding design, the top half can be flipped all the way to
the back of the calculator, 72 (!) keys. User/system RPL (Reverse Polish Lisp) programming language. Many data types: Real numbers, complex numbers, real & complex vectors, real & complex matrices, lists, integer numbers up to 64 bits, strings. Symbolic equation manipulation (ie. differentiation, integration), structured programming, graphics. A wealth of builtin unit conversions. Numerical root finding (solver) and integration. Directoryoriented file system, online help catalog of builtin functions and unit conversions. Infrared printer port, works with the HP Infrared Printer. 
Original Pricing, Production  HP28C: 5.1.1987 ($235)  1/1988 ($235) HP28S: 4.1.1988 ($235)  1.4.1992 ($195) 
Batteries  3xN 
Dimensions  Length 15.9cm, Width 9.4cm (closed), 18.9cm (open) Height 1.8cm (closed) 
Links  HP28C
Reference Manual, Jan 1987 (PDF) HP28C Getting Started Manual, Jan 1987 (PDF) HP28S Owner's Manual, Nov 1988 (PDF) HP28S Reference Manual, Nov 1988 (PDF) A number of interesting programs (PDF) HP28S Software Power Tools (PDF) Quick Reference (PDF) StepbyStep Solutions For Your HP Calculator, Calculus, HP28S, HP28C (English) 2.6.1988 StepbyStep Solutions For Your HP Calculator, Probability and Statistics, HP28S, HP28C (English) 1.11.1987 StepbyStep Solutions For Your HP Calculator, Vectors and Matrices, HP28S, HP28C (English) 3.6.1989 HP28C Hardware I/O Basics (MoHPC) Utility Programs. HP28COM Serial Interface. Infrared Interface Format. Power Consumption. Available Accessories. 
Comments  The HP28C was Hewlett Packard's first unit using the RPL
programming language. What a device! The designes really put a lot of thought in this powerful unit, see special features above. Despite all this power and the vast number of functions is the HP28 fairly easy to use  at least after spending a small initial effort needed to understand the basic concepts. There's really not much missing except maybe that its response on inputs feels a bit sluggish. Also  more importantly  its programming model is missing the Cstyle BREAK instruction needed for early termination of FORNEXT, DOUNTIL and WHILEREPEAT loops. And although it had an infrared printer port it lacked the HP41C's famous I/O capabilties. Nevertheless, it was HP's only true pocketsized calculator that offered the powerful RPL language. All other RPL models (HP48/49/50) were quite big. Only the HP41C and HP42S offered a sufficiently powerful keytrokebased programming model with arbitrary program names that allowed to build entire program libraries. HP's later pocketsized models (HP32S/II, HP33S, HP35S) had a rather restricted "A...Z" program naming scheme. Software:

Software Bugs  Version 1BB bugs (thanks to C. Finseth):
Memory LostSolve for A without an initial guess. You will get a System Halt.
character displays as

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