Hewlett-Packard HP-27S

Datasheet legend
Ab/c: Fractions calculation
AC: Alternating current
BaseN: Number base calculations
Card: Magnetic card storage
Cmem: Continuous memory
Cond: Conditional execution
Const: Scientific constants
Cplx: Complex number arithmetic
DC: Direct current
Eqlib: Equation library
Exp: Exponential/logarithmic functions
Fin: Financial functions
Grph: Graphing capability
Hyp: Hyperbolic functions
Ind: Indirect addressing
Intg: Numerical integration
Jump: Unconditional jump (GOTO)
Lbl: Program labels
LCD: Liquid Crystal Display
LED: Light-Emitting Diode
Li-ion: Lithium-ion rechargeable battery
Lreg: Linear regression (2-variable statistics)
mA: Milliamperes of current
Mtrx: Matrix support
NiCd: Nickel-Cadmium rechargeable battery
NiMH: Nickel-metal-hydrite rechargeable battery
Prnt: Printer
RTC: Real-time clock
Sdev: Standard deviation (1-variable statistics)
Solv: Equation solver
Subr: Subroutine call capability
Symb: Symbolic computing
Tape: Magnetic tape storage
Trig: Trigonometric functions
Units: Unit conversions
VAC: Volts AC
VDC: Volts DC
Years of production: 1988-1990 Display type: Graphical display  
New price: USD 110.00   Display color: Black  
    Display technology: Liquid crystal display 
Size: 6"×3"×½" Display size:  pixels
Weight: 6 oz    
    Entry method: Algebraic with precedence 
Batteries: 3×"LR44" button cell Advanced functions: Trig Exp Hyp Lreg Solv Fin Cmem RTC Snd BaseN 
External power:   Memory functions: +/-/×/÷ 
I/O: IR output     
    Programming model: Formula programming 
Precision: 12 digits Program functions: Jump Cond  
Memories: 6912(0) bytes Program display: Formula display  
Program memory: 6912 bytes Program editing: Formula entry  
Chipset: Saturn   Forensic result:  

hp27s.jpg (25177 bytes)The HP-27S is one of the most unusual in Hewlett-Packard's Pioneer series of calculators. It is a do-everything scientific calculator with a significant amount of user memory; however, it is not a keystroke-programmable machine. Programming/customization is accomplished through formulae and the "SOLVE" application.

Just how do-everything a machine is it? Well, judge for yourself. The uncluttered keyboard may mislead you; this machine has a full compliment of scientific functions and a lot more. It has a real-time clock and calendar. A beeper. An infrared printer port. Hexadecimal/octal/binary modes of operation. Probability and statistics. Even financial functions (TVM.) Add to that nearly 7 kilobytes of user memory to be used for variables and formulae, and you have a pretty powerful package (in fact, its parameters are comparable to those of the fabled HP-42S.)

But no real programmability. Although it does have the capability of conditional execution and loop structures inside formulae, those are a poor substitute for proper program capability. Or are they? This calculator apparently does have many fans who believe that this, in fact, is one of the best designed machines HP ever made. And considering that it is indeed a very good calculator, who am I to argue? What a pity it's gone extinct years ago, along with the HP-42S and other fabulously good HP models...

Demonstrating the formula programming model of this calculator, here is another implementation of my favorite example, the Gamma function. This implementation actually uses an undocumented feature found on several HP calculators equipped with "SOLVE", the L-function, which allows you to define a local formula within another and reuse it later. With its help, the formula below incorporates an iteration that extends its range to all real arguments including negative numbers: