HP 25C: A Calculator Worth C-ing

The HP 25C handheld calculator was Hewlett-Packard’s first programmable handheld product with “continuous memory,” meaning that it could retain information after the device was turned off without requiring a memory card. Hewlett-Packard would continue to use the “C” designation to denote continuous memory. When the company dropped the C suffix from its calculators in 1988, it did so because the feature had become such an essential component of scientific and business calculators that it went without saying.