The C.Itoh 8005 is a handheld calculator from 1975. It measures about 85mm by 135mm, with a depth between 25-32mm. The total weight is 136g without batteries. Power comes from 4 AA batteries, or it can use a 6V DC 0.5W adapter that plugs into a socket on the top-right side.
The case is made of glossy black plastic in two parts. The green plastic display filter sits flush with the case and tilts at a 20 degree angle. Below this is a metallic sticker for the C.Itoh brand name and model number. The keyboard has soft, squishy multi-colored keys that work reasonably well. However, the grey keys lack contrast with the white lettering.
The display is an 8-digit green vacuum fluorescent display, with a 9th digit used for negative signs and error indicators. Features are basic, including the four standard math functions, percentages, square root, pi, and a change sign key.
Inside, the C.Itoh 8005 uses common 1970s era components like a NEC microprocessor, diodes, transistors, resistors and capacitors. There are two circuit boards – one for the keyboard and one for the main logic.
The calculator handles negatives by showing a minus sign in the leftmost 9th digit, allowing full 8-digit negative numbers. Overflow and divide-by-zero errors display codes in the 9th digit but are not recoverable. Constant operation is automatic for all four functions. Overall, the C.Itoh 8005 is a competent mid-1970s handheld calculator, but lacks more advanced features found in competing models. The chief drawback is the lack of overflow recovery.
