It is difficult to identify the oldest computer still in production use since there are different definitions of what constitutes a computer and what it means to be "still in production use." However, one example of an old computer still in use is the Harwell Dekatron (also known as WITCH), which was built in 1951 and is currently on display at The National Museum of Computing in the UK. The computer was used for scientific calculations and was decommissioned in 1973, but was restored to working order in 2012 and is now demonstrated to visitors at the museum. While the Harwell Dekatron is no longer in active use, it is considered to be the world's oldest original working digital computer.