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1980s Computers Explanation of terms

The HP-75



Hewlett Packard (US)


HP-75C and HP-75D

Date Launched

September 1982 (HP-75C)
1984 (HP-75D)


£750 (75C in early 1984)

Microprocessor type

Capricorn (HP's custom-designed 8-bit processor)

ROM size

48 kilobytes
3 slots for additional ROMS, including a word processor.

Standard RAM

16 kilobytes (75C) / 32KB (76D)

Maximum RAM

Not known

Keyboard type

Almost full size, typewriter style.
Unlike other pocket computers it was possible to touch-type on the HP-75's keyboard.

Supplied language

Extended BASIC

Text resolution

1 line of 32 characters on LCD display

Graphics resolution

160 x 9 pixels

Colours available


Example Screenshot

HP-75 LCD display
As with most early pocket computers, the display was the biggest limitation.



Cassette load speed

Had a built-in magnetic card reader, hand-pulled, storing 1.3 kilobytes per card.

Dimensions (mm)
Weight (grams)

254 x 127 x 32

Special features

Compact size.
Had a cut-down version of the popular Visicalc spreadsheet included in the ROM.
The HP-75D came with a wand for reading bar codes.

Good points

Used Hewlett Packard's Interface Loop to connect up to 30 peripherals, such as a VDU, printer, modem, tape recorder...

Bad points

Capacity of the magnetic cards was too small.
A bit too big and heavy to be a true 'pocket' computer.

How successful?

The HP-75D was popular for stock control in business and was also sold to US government agencies, but was not aimed at the home market.


Hewlett Packard designed the HP-75 to be a small, portable computer with all the power of a desktop machine of the time.
It had an appointments calendar with audible alarms so could also be considered a very early PDA.
Like the Hewlett Packard calculators before it the HP-75 was solidly constructed.

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