A member of HP's Pioneer series, the 20S was a low cost model targeted at students, using the same hardware as the HP-10B business calculator.

Despite these limitations, the 20S is keystroke programmable, supporting up to 99 program lines of fully merged instructions and ten memory registers.

The retail price set a new bar for HP, who credited their delivery of a low-price product to tight integration between their research, development and manufacturing departments.

The initial design used blue and orange shift keys, but a visual refresh in 1999 changed the color scheme to green and purple.

[4][5] The majority of the features of the 20S are still present, including keystroke programming support and the typical trigonometric, logarithmic and exponential functions found on most scientific calculators.