Radio Shack PC-7

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:   Display type: Alphanumeric display  
New price:   Display color: Black  
    Display technology: Liquid crystal display 
Size: 5½"×3½"×½" Display size: 12 characters
Weight: 5 oz    
    Entry method: BASIC expressions 
Batteries: 2×"CR-2032" Lithium Advanced functions: Trig Exp Cmem 
External power:   Memory functions:  
I/O: Expansion port     
    Programming model: BASIC 
Precision: 12 digits Program functions: Jump Cond Subr Lbl Ind  
Memories: 26(0) numbers Program display: Text display  
Program memory: 512 bytes Program editing: Text editor  
Chipset: Casio fx-5200P   Forensic result: 9.00000716758  

pc7.jpg (51504 bytes)Just how useful is a BASIC-programmable calculator with only 512 bytes of memory? Not very useful, which is probably why my Tandy PC-7, really just a Casio fx-5200P in OEM packaging, comes equipped with a memory expansion module, bringing the total amount of available memory up to a whopping 1.5 kilobytes. Yes, folks, that's 1500 characters worth of text! Almost an entire page!

Okay, I'm not trying to make fun of this little machine. It is an excellent scientific calculator after all, and its BASIC programmability provides useful additional functionality.

The following program is a small footprint, yet accurate implementation of the Gamma function, demonstrating the PC-7's programming model:

20 Z= ABSX
30 G=1
40 IF Z>9 THEN 80
50 G=G*Z
60 Z=Z+1
70 GOTO 40
80 G=( LNZ+ LN SQR(Z* HYP SIN(1/Z)+1/810/Z^6)-1)*Z-LNG
90 G=G+ LN SQR(2*π/Z)
100 IF X>0 THEN 120
110 G= LN(-π/X/ SIN(π*X))-G