The humble handheld calculator, first developed by a small team at Texas Instruments, has just turned 40.

Examples of the first two programmable calculators, the TI-58 and TI-59, have been added to the Smithsonian's National Museum of American History to celebrate the anniversary.

"The National Museum of American History has a significant role in preserving the innovations that have shaped maths education throughout history," said museum director Brent Glass.

"Texas Instruments is a leader in maths education, and we hope that its history of invention and innovation will inspire visitors and scholars."

The TI-58 and TI-59 calculators will join objects and materials previously donated by the company, including a prototype for the world's first miniature electronic handheld calculator for which Texas Instruments filed a patent application in 1967.

The prototype performed four functions (addition, subtraction, multiplication and division), had 12 bytes of memory, ran on batteries and was cased in solid aluminium. It weighed nearly 3lbs.

It was a major advance compared to existing electronic calculators, which were approximately the size of a typewriter and needed to be plugged into a power source to operate.

Melendy Lovett, president of Texas Instruments' Education Technology division, donated the objects to the collection, and two of the calculator's inventors, Jerry Merryman and James Van Tassel, attended the ceremony.

"We are proud of our long history of working with the Smithsonian to document and preserve the continuing evolution of educational technology," said Lovett.