DEF EOF(f)
    IF END #f THEN LET EOF = -1 ELSE LET EOF = 0
END DEF

FUNCTION checknospaces(s$)
    FOR i = 1 TO LEN(s$)-1
        IF (s$)[i:1] = CHR$(32) OR (s$)[i:1] = CHR$(9) THEN LET checkNoSpaces = 0
    NEXT i
    LET checknospaces = 1
END FUNCTION

OPEN #1: NAME "m:\input.fasta", org text, ACCESS INPUT, create old

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