HP 33s

The HP 33s was a scientific calculator marketed by Hewlett-Packard. It was introduced in 2003 as the successor to the HP 32SII, and discontinued on the introduction of its successor, the HP 35s in 2007.

Features

Its main features are:

RPN or traditional semi-algebraic, user-selectable
Two-line LCD display
Full scientific/engineering mathematical features
Keystroke-programmable with full boolean and program-control command sets and line edit, insert and delete
HP "equation list" equation editor in both the stand-alone list as well as in keystroke programs
HP Solver feature
Function integration feature
All mathematical operations and features fully functional in all modes
Unit conversion and constants
31 KB of random-access user memory

The main differences from the HP 32SII are:

A radical difference in keypad layout and appearance
Memory is expanded from 2 KB to 32 KB
Faster processor
More functions
Algebraic entry mode as well as RPN
The display has two lines
The length of an equation was now restricted to 255 characters

The HP 33s was co-designed and manufactured by Kinpo Electronics of Taiwan.

Reception

The HP 33s is generally considered to have fewer logic bugs than the HP 35s. However, the unconventional chevron-styled keypad has been regarded by reviewers as bizarre and difficult to use compared to other HP professional calculators.

Revisions

The 33s went through numerous revisions that have solved two of the most pervasive issues people had with the early models.