The Museum of HP Calculators
Friden SRW Keyboard
The Friden SRW keyboard had a 100 key array in which numbers to be added,
subtracted and divided were entered. To the left of this array was a 10
key array in which multipliers were entered. A small register
directly above the multiplier keypad showed the number entered there.
Control keys near the large keyboard included:
- Plus (+)
- Added the amount in the keyboard to the upper dials.
- Minus (-)
- Subtracted the amount in the keyboard from the upper dials.
- Two Divide Keys (both labeled identically)
- Both keys were pressed together to divide. Why? Apparently because
Friden's chief competitor managed to get a patent on a single key
- Left and Right Shift keys (<O O>)
- Shifted the carriage left and right.
- Square Root keys - 11 of them
- There were 11 keys at the base of the main keyboard.
These allowed the user to specify the location of the decimal
point (since the roots 25 and 250 don't have the same digits) and start
the square root process.
- Add Key (ADD)
- Determined whether the keyboard was cleared after an operation. With the
key in the up position, it was necessary to press the Keyboard Clear key
to clear the keyboard. Otherwise, the keyboard was cleared on each addition.
- Keyboard Clear (KB CLEAR)
- Cleared the large keyboard.
- Carriage Clear (CARR CLEAR)
- Cleared the registers in the carriage and returned the carriage to position
- Keyboard Lock (KB LOCK)
- Locked the entire keyboard.
Also prevented entry of keyboard value into upper register when using the
Enter Dividend key.
- Enter Dividend (ENTER DIVD)
- Cleared the registers, set the carriage to a predefined position and
entered the dividend in the upper dials. Also prevented the 1 from appearing
in the counter as it would during a normal add. Finally, it cleared
the keyboard for entry of the divisor.
- Division Stop (DIV STOP)
- Stopped a division in progress. Handy after accidentally asking the
machine to divide by zero which would otherwise run forever.
Control keys near the smaller multiply keyboard included:
- Multiply (MULT)
- Cleared the multiply display, performed the multiplication and cleared the
- Accumulate Multiply (ACCUM MULT)
- performed a multiplication in which the product and multiplier
added to the products and multipliers already in the registers. Then
cleared the keyboard.
- Negative Multiply (NEG MULT)
- Like a accumulate multiply but it subtracted the product and multipliers.
- Multiplier Repeat (REP)
- Locked the multiplier in the register so it could be reused.
- Multiplier Clear (MULT CLEAR)
- Cleared the multiplier register.
- Non-Entrey (NON ENT)
- Prevented the entry of multipliers into the lower carriage register.
- Counter Control (CTR CON)
- Reversed the sense of the counter (the lower carriage register.)
(i.e. additions would now decrement the counter.)
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