Which calculator product innovation in the 1970s caused a retail revolution and dramatically changed mathematics education?

The calculator market has transformed mathematics education and professional work for decades. From basic arithmetic devices to advanced graphing tools, these products have evolved dramatically, creating billion-dollar industries and changing how mathematics is taught and practiced. This trivia question explores a pivotal moment in calculator retail history that revolutionized the industry and mathematics education forever.

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Texas Instruments TI-30, the first affordable scientific calculator for students ($25 in 1976, equivalent to about $120 today)
Hewlett-Packard HP-35, the first handheld scientific calculator (but priced at $395 in 1972, nearly $2,500 in today's money)
Casio fx-7000G, the world's first graphing calculator (released in 1985, after the major educational shift had already begun)
Sharp EL-8, the first portable calculator using LCD display (launched in 1973 but was too expensive for mass educational adoption)