FUNCTION checkNoSpaces (s$)
    FOR i = 1 TO LEN(s$) - 1
        IF MID$(s$, i, 1) = CHR$(32) OR MID$(s$, i, 1) = CHR$(9) THEN checkNoSpaces = 0
    NEXT i
    checkNoSpaces = 1
END FUNCTION

OPEN "input.fasta" FOR INPUT AS #1

first = 1

DO WHILE NOT EOF(1)
    LINE INPUT #1, ln$
    IF LEFT$(ln$, 1) = ">" THEN
        IF NOT first THEN PRINT
        PRINT MID$(ln$, 2); ": ";
        IF first THEN first = 0
    ELSEIF first THEN
        PRINT : PRINT "Error : File does not begin with '>'"
        EXIT DO
    ELSE
        IF checkNoSpaces(ln$) THEN
            PRINT ln$;
        ELSE
            PRINT : PRINT "Error : Sequence contains space(s)"
            EXIT DO
        END IF
    END IF
LOOP
CLOSE #1