All early Texas Instruments calculators, including the SR-52 and the TI-59 used the INV key for many functions: INV SBR to return from a subroutine, INV Ln to calculate the exponential, or INV EE to cancel scientific display mode are just some of the examples of this key's usage. The TI-88 is no exception; there are many uses of the INV key on this machine, some of them less than obvious.

INV Σ+   Remove statistics data point
INV P-R   Rectangular to polar conversion
INV OP nn   Display OP code function (do not execute)
INV CMs   Clear program memory
INV SBR   Subroutine return
INV Log   Common antilogarithm
INV Ln   Natural antilogarithm
INV GFR   Go backward relative
INV EE   Cancel scientific display mode
INV Time   Display date
INV Eng   Cancel engineering display mode
INV Fix   Cancel fixed-point display mode
INV Int   Calculate fractional part
INV DRG   Set to degrees mode
INV If>   If less than
INV If=   If not equal
INV Dsz   Decrement and execute on zero
INV IfF   If flag not set
INV StF   Clear flag
INV sin   Arc sine
INV cos   Arc cosine
INV tan   Arc tangent
INV Lst   List data memories
INV Prt   Advance printer
INV Trc   Cancel trace mode