Texas Instruments TI-83 PLUS - Manual (Page 495)

TI-83 Plus CATALOG, Strings, Hyperbolic Functions 492
inString(
inString( returns the character position in string of the first character of
substring . string can be a string or a string variable. start is an optional
character position at which to start the search; the default is 1.
inString( string , substring [ , start ] )
Note: If string does not contain substring , or start is greater than the length of
string , inString( returns 0 .
length(
length( returns the number of characters in string . string can be a string or
string variable.
Note: An instruction or function name, such as sin( or cos( , counts as one
character.
length( string )