INSTR searches for the occurrence of one string in another, and returns with the position of the first match.
Y = INSTR ([X]A$,B$) 1<X<255
10 A$ = "BASICS" 20 PRINT INSTR (A$,"S")
This program will print 3, since this is the first occurrence of the letter S.
10 A$ = "SUPER BASICS" 20 B$ = "SI" 30 PRINT INSTR(A$,B$)
This program will print 9 as the first occurrence of SI.
10 A$ = "BASICS" 20 PRINT INSTR(4,A$,"S")
The above program will print 6, since this is the first occurrence of the letter S from the fourth character onwards in the string A$.
If B$ does not occur in A$, then 0 is returned. X, which is optional and defaults to 1, is used to start the search at a particular place within a string.
Case is also important, i.e. “s” is not the same as “S”.