Source code in the basic programming language

first$ = "qwertyuiop"

'Determining if the first string starts with second string
second$ = "qwerty"
IF LEFT$(first$, LEN(second$)) = second$ THEN
    PRINT "'"; first$; "' starts with '"; second$; "'"
ELSE
    PRINT "'"; first$; "' does not start with '"; second$; "'"
END IF

'Determining if the first string contains the second string at any location
'Print the location of the match for part 2
second$ = "wert"
x = INSTR(first$, second$)
IF x THEN
    PRINT "'"; first$; "' contains '"; second$; "' at position "; x
ELSE
    PRINT "'"; first$; "' does not contain '"; second$; "'"
END IF

' Determining if the first string ends with the second string
second$ = "random garbage"
IF RIGHT$(first$, LEN(second$)) = second$ THEN
    PRINT "'"; first$; "' ends with '"; second$; "'"
ELSE
    PRINT "'"; first$; "' does not end with '"; second$; "'"
END IF


10 A$ = "THIS, THAT, AND THE OTHER THING"
20 S$ = "TH"
30 DEF FN S(P) = MID$(A$, P, LEN(S$)) = S$
40 PRINT A$ : PRINT

110 S$(1) = "STARTS"
120 S$(0) = "DOES NOT START"
130 PRINT S$(FN S(1))" WITH "S$ : PRINT

210 R$ = "" : FOR I = 1 TO LEN(A$) - LEN(S$) : IF FN S(I) THEN R$ = R$ + STR$(I) + " "
220 NEXT I
230 IF LEN(R$) = 0 THEN PRINT "DOES NOT CONTAIN "S$
240 IF LEN(R$) THEN PRINT "CONTAINS "S$" LOCATED AT POSITION "R$
250 PRINT

310 E$(1) = "ENDS"
320 E$(0) =  "DOES NOT END"
330 PRINT E$(FN S(LEN(A$) - LEN(S$) + 1))" WITH "S$