1    * The standard Apple II "Air-raid" bell has
                2    * been replaced with a gentler tone. Use it
                3    * to give users some aural feedback that
                4    * they are using a ProDOS program.
                5    * The code for it follows.
                6    *
                7    SPKR     EQU   $C030      ;this clicks the speaker
                8    *
8000: 00        9    LENGTH   DS    1          ;duration of tone
                10   *
                11   * This is the wait routine from the Monitor ROM.
                12   *
8001: 38        13   WAIT     SEC              
8002: 48        14   WAIT2    PHA              
8003: E9 01     15   WAIT3    SBC   #1         
8005: D0 FC     16            BNE   WAIT3      
8007: 68        17            PLA              
8008: E9 01     18            SBC   #1         
800A: D0 F6     19            BNE   WAIT2      
800C: 60        20            RTS              
                21   *
                22   * Generate a nice little tone
                23   * Exits with Z-flag set (BEQ) for branching
                24   * Destroys the contents of the accumulator
                25   *
800D: A9 20     26   BELL     LDA   #$20       ;duration of tone
800F: 8D 00 80  27            STA   LENGTH     
8012: A9 02     28   BELL1    LDA   #$2        ;short delay...click
8014: 20 01 80  29            JSR   WAIT       
8017: 8D 30 C0  30            STA   SPKR       
801A: A9 20     31            LDA   #$20       ;long delay...click
801C: 20 01 80  32            JSR   WAIT       
801F: 8D 30 C0  33            STA   SPKR       
8022: CE 00 80  34            DEC   LENGTH     
8025: D0 EB     35            BNE   BELL1      ;repeat LENGTH times
8027: 60        36            RTS              

--End assembly, 40 bytes, Errors: 0