Hewlett Packard HP-25/25C

Serial Number HP-25: 1509S35151: 1975, 9th week, Singapore
Accessories None, battery pack missing
Condition Excellent front. One of the battery contacts broke off and has not very professionally been replaced with a piece of wire.
Repairs 29.1.2003 Fixed the broken battery contact with a sturdy unflexible metal piece. Works perfectly now.
Acquired 13.1.2003
Serial Number HP-25C 1803S23471: 1978, 3rd week, Singapore
Accessories Power supply

External charging station for battery pack

Battery pack, modified so that regular and rechargeable AA batteries can be inserted

Manual: HP-25 Bedienungshandbuch (German)

HP-25 Programmsammlung (German, Software listings) 

Pouch

Original protecting box

Manual: HP-25 Owner's Handbook, bound printout from the MoHPC CD-ROM
Condition Mint except for a small scratch on the display
Repairs Cut open the battery pack so that it can now be stuffed with rechargeable or normal batteries
Acquired 5.6.2002
Serial Number HP-25C: 1803S23994: 1978, 3rd week, Singapore
Accessories None, even the battery pack is missing
Condition Extremely dirty on arrival. Two large numbers "19" painted on top and bottom side of the unit. One battery contact broke off when I touched it. Unit non-functional.
Repairs, Comments 25.2.2003 Cleaned the unit as much as possible. Had to use strong solvent to get rid of the numbers.
26.2.2003 Fixed the broken battery contact. Unit is now fully functional, all LED digits are ok. Swapped display with the broken one from my HP-21. Now the top segment of the 4th digit from the left is missing in the display of this HP-25C (see picture).
Acquired 16.2.2003, sold 29.9.2004
.
HP codename, series Squash (HP-25), Squish (HP-25C), Woodstock
Type, Precision, Input Mode Scientific, 10 BCD digits, exponent ±99, Reverse Polish Notation.
The precision of these models is extremely poor, see table below! As far as I can tell they all yield exactly the same results. Interestingly, the HP-35 shows the very same results! Apparently, they're using the same software.
Programmable 50 steps, partially merged. No subroutines. No program editing except overwrite. No labels. Branching only to line numbers
Performance Index 1.6 (HP-25C)
Memory Permanent memory (HP-25C only). 8 registers (0..7). Stack registers not permanent.
Display 11 digit 7 segment red LED plus sign
Special features One of the first progammable pocket calculators with nonvolatile storage for program and data.
Original Pricing, Production HP-25: 1.8.1975 ($195) - 1.5.1978 ($125)
HP-25C: 1.7.1976 ($195) - 1.5.1978 ($125)
Batteries Battery pack with 2x AA sized cells or accus or power supply
Dimensions Length 12.7cm, Width 6.5cm, Height 2.9cm
Links HP-25 Owner's Handbook, May 1975 (PDF)
Quick Reference (PDF)
Book: Rechenverfahren für den Taschenrechner HP-25.
Comment The HP-25 was Hewlett Packard's eigth calculator, the third programmable one after the HP-65 and HP-55 and the first programmable Woodstock. The HP-25C was the first unit using "continuous memory".
A top-notch unit when it was introduced. Today still a versatile unit although the programming capabilities are very limited. Comparable to the HP-55 classic model.

Calculation
 Correct result
 HP-25 Result
 Error
100/18 
40/9 
5.555555*0.5555555
40/9+50/9000 
sqrt(2E6)/1000
 exp(0.005) 
exp(0.999999) 
exp(1.000001) 
exp(100)/1E43
 ln(1E-6)/10
 ln(0.9995)*10000 
ln(1.0005)*10000
 pow10(0.005) 
pow10(0.99999) 
pow10(1.00001)/10 
pow10(80.1)/1E80 
log10(2E-8) 
log10(0.9995)*10000 
log10(1.0005)*10000 
log10(1000100) 
2^40 / 1E12 
2^1.443 
1.000001^1E6 
sin(0.01 rad)*1000 
sin(1 rad)*10 
sin(1.5608 rad)*10 
sin(800 rad)*10 
tan(0.01 rad)*100 
tan(1 rad) 
tan(1.5708 rad)/1E5 
tan(800 rad) 
asin(0.01)*100,rad 
asin(0.5)*10,rad 
asin(0.999),rad 
asin(0.99999),rad
atan(0.01)*1000,rad 
atan(0.9999)*10,rad 
atan(1.0001)*10,rad 
atan(1E4),rad 
sin(0.01 deg)*10000 
sin(50 deg)*10 
sin(89.9 deg)*10 
sin(5000 deg)*10 
tan(0.01 deg)*10000 
tan(50 deg) 
tan(89.99 deg)/1000 
tan(5000 deg)*10 
asin(0.01 deg)*10 
asin(0.5 deg)/10 
asin(0.999 deg)/10 
asin(0.99999 deg)/10
atan(0.01 deg)*10 
atan(0.9999 deg)/10 
atan(1.0001 deg)/10 
atan(1E4 deg)/10 		 +5.555555555 555555556
+4.444444444 444444444
+3.086419135 802500000
+4.450000000 000000000
+1.414213562 373095049
+1.005012520 859401063
+2.718279110 178575917
+2.718284546 742232836
+2.688117141 816135448
-1.381551055 796427410
-5.001250416 822979193
+4.998750416 510479141
+1.011579454 259898524
+9.999769744 141629304
+1.000023026 116026881
+1.258925411 794167210
-7.698970004 336018805
-2.172015458 642557997
+2.170929722 302082819
+6.000043427 276862670
+1.099511627 776000000
+2.718856483 813477575
+2.718280469 319376884
+9.999833334 166664683
+8.414709848 078965067
+9.999500371 413582332
+8.939696481 970214179
+1.000033334 666720637
+1.557407724 654902231
-2.722418084 073540959
-1.994900160 845839293
+1.000016667 416711313
+5.235987755 982988731
+1.526071239 626163188
+1.566324187 113108692
+9.999666686 665238206
+7.853481608 973649763
+7.854481608 975316429
+1.570696326 795229953
+1.745329243 133368033
+7.660444431 189780352
+9.999984769 132876988
-6.427876096 865393263
+1.745329269 716252907
+1.191753592 594209959
+5.729577893 130590236
-8.390996311 772800118
+5.729673448 571526491
+3.000000000 000000000
+8.743744126 687686209
+8.974376527 084057279
+5.729386976 834859268
+4.499713506 778012245
+4.500286464 574097998
+8.999427042 206779036		 +5.555555556
+4.444444444
+3.086419136
+4.45000000
+1.414213562
+1.005012521
+2.718279110
+2.718284546
+2.688117141
-1.381551056
-5.001250000
+4.998750000
+1.011579454
+9.999769742
+1.000023026
+1.258925350
-7.698970003
-2.172015278
+2.170929541
+6.000043426
+1.099511625
+2.718856482
+2.718281828
+9.999833318
+8.414709848
+9.999500372
+8.939696951
+1.000033333
+1.557407724
-2.722570106
-1.994900681
+1.000016664
+5.235987757
+1.526071240
+1.566324187
+9.999666686
+7.853481609
+7.854481610
+1.570696327
+1.745328987
+7.660444432
+9.999984769
-6.427876027
+1.745329013
+1.191753592
+5.729569869
-8.390996161
+5.729673428
+3.000000001
+87.43744128
+89.74376526
+5.729386976
+4.499713507
+4.500286465
+8.999427042
 0
0
0
0
0
0
0
     1E-9
     1E-9
0
   416E-9
   416E-9
0
     2E-9
0
    62E-9
     1E-9
   181E-9
   181E-9
     1E-9
     3E-9
     2E-9
  1359E-9
    16E-9
0
     1E-9
   469E-9
     2E-9
     1E-9
152022E-9
   520E-9
     3E-9
     1E-9
0
0
     1E-9
0
     1E-9
0
   256E-9
     1E-9
0
    70E-9
   257E-9
     1E-9
  8024E-9
   151E-9
    21E-9
     1E-9
     1E-9
     1E-9
     1E-9
0
0
0


Back To Contents