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Calculators: Handheld: National Semiconductor 835A
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Size (approx): | 68mm
(max) x 140mm x 22mm (max) (w,h,d) Weight 62g excluding batteries |
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Power: |
9.0V DC, 1xPP3 size battery. Also accepts adapter (undefined) through a socket on the left hand side, about mid way up. | ||
| Case: | Rounded wedge-shaped case made from a two-piece matt brown plastic case. The red plastic display filter is inset and sculptured to form a tilted section. This gives a bright but limited viewing angle image. The keyboard surround is a textured plastic panel in cream and brown with reversed out text labels for the switch, keys, brand and model number. The small keys are short travel, rocking action, with a soft positive click. | ||
| Display: | 8 digit red LED with bubble lens and no ninth digit | ||
| Features: | Four function with percentages and four function memory | ||
| Age: | 1978 | ||
| Manufacturer: | Made in Hong Kong, no serial number that I can find. | ||
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Comments:
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Incredibly empty calculator for its age. Low component count (chip and display) to keep the costs down to a minimum. The logic is reasonable with good recovery but let down by seven digit negative numbers, odd memory overflow and the pseudo fixed decimal bug. See a similar design but quite different calculator in the 835 model. |
| Components: | 1 x cpu: Texas TMS0972NL MBT
7845 Singapore (date code week 45 of 1978) 28 pin DIL 0.6" width
black plastic 1 x 8 digit (nine bubble lens) LED unit No other components |
| Boards: | Keyboard unit is attached to front of the calculator and fixed to the main board (1032) by 16 rigid wires in a plastic strip. The very small main board floats free with the IC and display. There are no other components. |
| Construction: | Remove the four screws on the back. The two piece case then separates easily. |
| Logic comments: | (CE/C) cancels an incorrect numerical entry, pressing a second time clears the calculator |
| Input overflow is suppressed, keying in a ninth digit is ignored | |
| There is automatic constant on all four functions | |
| Overflow shows the result flashing which is recoverable using (CE) | |
| Divide by zero shows zero flashing which is recoverable using (CE) | |
| Negative numbers are shown with a "-" to the immediate left of a number but as there is no ninth digit to travel into you are limited to seven digit negative numbers | |
| There is no indication of memory store - you have to remember it | |
| Overflow in memory causes a flashing number, which takes several (C) presses to correct and clears the memory | |
| It suffers the pseudo fixed decimal bug: key in (1)(+)(.)(0)(0)(0)(=) to give "1.000" which remains a fixed three digit number until you need more digits or use multiply or divide |
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The box is 70mm by 148mm and x 27 mm deep, not much bigger than the calculator. It is printed in black and brown which matches the calculator rather well. There is no country of origin on the box. |
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