Text: VOWEL

       Name: VOWEL                                                   [Show more]
       Type: Subroutine
   Category: Text
    Summary: Test whether a character is a vowel
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * MT17 calls VOWEL


 Arguments:

   A                    The character to be tested


 Returns:

   C flag               The C flag is set if the character is a vowel, otherwise
                        it is clear


.VOWEL

 ORA #%00100000         ; Set bit 5 of the character to make it lower case

 CMP #'a'               ; If the letter is a vowel, jump to VRTS to return from
 BEQ VRTS               ; the subroutine with the C flag set (as the CMP will
 CMP #'e'               ; set the C flag if the comparison is equal)
 BEQ VRTS
 CMP #'i'
 BEQ VRTS
 CMP #'o'
 BEQ VRTS
 CMP #'u'
 BEQ VRTS

 CLC                    ; The character is not a vowel, so clear the C flag

.VRTS

 RTS                    ; Return from the subroutine