year 1977

TI-30 is a scientific calculator introduced in 1997 and was notable for its extremely low cost, around $25.
It may be the best-selling calculator ever, with an expected 15,000,000 manufactured during its lifespan from 1976-1983.
The original TI-30 had a LED display, was powered by a 9V battery, and contained nearly all of its functionality in only one chip. It could do just about all the log and trig functions of an HP-35. It pioneered algebraic notation with precedence and parentheses which is now favored by all but the most die-hard RPN fanatics, and takes significantly more logic to implement. A user could type in (2 + 2) + 3 * 3 = and get the correct result.