Returns the position of the first occurrence of a string in another string.
 
INSTR([start%,]stringexpression1$,stringexpression2$)
 
    - start%                Sets the character position where the search
                            begins. If start% is omitted, INSTR starts at
                            position 1.
    - stringexpression1$    The string to search.
    - stringexpression2$    The string to look for.
 
Example:
    a$ = "Microsoft QBasic"
    PRINT "String position ="; INSTR(1, a$, "QBasic")
 
See Also    <LEFT$, RIGHT$>    <LEN>    <MID$>