Comment by stonemetal12

They are not "older models" just lower end. TI-92 came out in 1995 and discontinued in in 1998. TI-83 was introduced in 1996 and discontinued in 2004. TI-89 came out in 1998 and was discontinued in 2004.

At my high school we were allowed to have TI-83s but not TI-89s, because 89s had built in CAS (computer algebra system) and could do your algebra homework for you. When I went to college I already had an 83 so I didn't feel the need to upgrade.