Hewlett-Packard HP-48SX

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: 1990  Display type: Graphical display  
New price:   Display color: Blue  
    Display technology: Liquid crystal display 
Size: 7"×3½"×1" Display size: 131×64 pixels
Weight: 10 oz    
    Entry method: Reverse Polish Notation 
Batteries: 3×"AAA" alkaline Advanced functions: Trig Exp Hyp Lreg Grph Solv Intg Ab/c Cplx Symb Fin Cmem RTC Snd Mtrx BaseN Units 
External power:   Memory functions: +/-/×/÷ 
I/O: Serial port, IR port, expansion ports     
    Programming model: Reverse Polish Language 
Precision: 12 digits Program functions: Jump Cond Subr Lbl Ind  
Memories: 32(0) kilobytes Program display: Text display  
Program memory: 32 kilobytes Program editing: Text editor  
Chipset: Saturn   Forensic result: 8.99999864267  

hp48sx.jpg (27882 bytes)The HP-48SX was the first of HP's current line of high-end graphic calculators. It was essentially an upgraded version of the HP-28S, with many new functions, a real-time clock and calendar, two extension ports that could accept ROM or RAM modules, a bidirectional infrared interface and an RS-232 port used to exchange data with other computers.

On the exterior, the HP-48SX looks more like traditional HP calculators; gone is the controversial clamshell design. The keyboard is very crowded, with three shift keys (gold, blue, and alpha); even so, most calculator functions can be accessed through soft keys only. The calculator itself feels sturdy, with easily accessible compartments for battery and extension cards. Despite the crowded keyboard, it's obviously a much better design than the HP-28S.

This calculator is not really a collector's item, not yet; it is, in fact, the calculator I've been using on an everyday basis for the last 6-7 years. Before I bought a portable computer, I actually used this machine as a personal organizer of sorts, with programs of my own creation, for taking financial data or addresses with me on the road. I also experimented with assembly language programming using tools released by HP, as well as some excellent third-party tools released into the public domain by other enthusiastic HP-48SX users. I remain very fond of this device, despite the fact that I still have trouble remembering the four-key sequence needed to recall the value of pi (it's gold-shift, pi, blue-shift, ->NUM, in case you're wondering.)

As a high-end scientific/engineering calculator, the HP-48SX has a built-in implementation of the Gamma function. More accurately, the calculator can calculate an extended factorial for any real number; the Gamma function of any real x can be obtained as the factorial of x-1.

Built-in Gamma function notwithstanding, my implementation can still be useful. The built-in version can only calculate the Gamma function for reals; the implementation shown here extends the definition of the function to the entire complex plane.

  -> x
    x 1
      OVER * SWAP 1 + SWAP
    SWAP DUP 1 + 76.1800917295 SWAP /
    OVER 2 + 86.5053203294 SWAP / -
    OVER 3 + 24.0140982408 SWAP / +
    OVER 4 + 1.23173957245 SWAP / -
    OVER 5 + 1.20865097387E-3 SWAP / +
    OVER 6 + 5.39523938495E-6 SWAP / -
    1.00000000019 + OVER  / π ->NUM 2 * √
    * LN SWAP DUP DUP 5.5 + LN SWAP .5 + *
    SWAP 5.5 + - + EXP SWAP /