This month marks the thirtieth anniversary of the Canon EOS system. EOS stands for "Electro Optical System," which was how Canon identified the new electronic lens mount that replaced their old mechanical one. The first EOS components were the EOS 640 SLR and 35-70mm f3.5-4.5, 50mm f/1.8, and 35-105mm f/3.5-4.5 lenses.
EOS blossomed into a digital force with the launch of the original EOS Digital Rebel (Kiss or 300D in some regions) in September 2003. Canon claims that from that point forward, the EOS mount has held the number one market share in ILC.
EOS has morphed a bit in the digital age, and is actually four distinct pieces: EOS EF (full frame DSLR), EOS EF-S (APC-C frame DSLR), EOS EF-M (APS-C frame mirrorless), and EOS Cine (Super35mm frame video).