Your Commodore - Commodore Is Awesome

Homework - answer I
MACHINE CODE
1000 *- $C000 1570 TA?
1010 BUFFER 8 3 0 1580 JMP LOOP4 ; NEXT WORD
1020 CHROUT - $FFD2 1590 NOTFOUND LDA #MESS4
1040 PRINTMESS - $ABlE 1610 JSR PRINTMESS
1050 PRINTNO - $BDCD 1620 LDA NcBUFFER
1060 COUNT - 899 1630 LDY #.>BUFFER
1070 1640 JSR PRINTMESS
1080 1650 RTS
1090 LDY #0 ; INITIALISE BUFFER 1 6 6 0 FOUND LDA #MESS1
1110 LOOP5 STA BUFFER,? 1680 JSR PRINTMESS
1120 INY 1690 LDA 4BUFFER
1140 BNE LOOP5 1710 JSR PRINTMESS
1150 LDA 4147 ; PRINT PROMPT 1 7 2 0 LDA 4MESS3
1240 BEQ LOOP2 1810 JSR PRINTMESS
1250 STA BUFFER,? 1820 RTS
1260 IN? 1830
1270 JMP LOOPI 1840
1280 LOOP2 CPY #4 ; IF WORD LESS THAN 1 8 5 0 TABLE .ASCI "TAKELOOKSINGEAT BITEKILL"
1290 BCS LOOP& ; FOUR CHARS THEN PAD 1 8 6 0 .ASCI "THROLIGHORINCLIMSWIMFICHDROP"
1300 LDA #32 ; IT WITH SPACES 1 8 7 0 TABLEN .BYTE 13
1310 STA BUFFER,? 1880 MESS1 .ASCI "THE WORD "
1320 IN? 1890 .BYTE 0
1330 JMP LOOP2 1900 MESS2 .ASCI " IS NUMBER "
1340 LOOP6 LDA #0 ; TERMINATE BUFFER WITH 1 9 1 0 .BYTE 0
1350 STA BUFFER,Y ; ZERO 1 9 2 0 MESS3 .ASCI " IN MY WORD L I S T "
1360 LDA #13 ; CARRIAGE RETURN 1 9 3 0 .BYTE 0
1370 JSR CHROUT 1940 MESS4 .ASCI "I DON'T RECOGNISE "
1380 1950 .BYTE 0
1390
1400 LDY *0 ; INITIALISE WORD COUNT
1410 STY COUNT
1420 LOOP4 LDX #0 ; SEARcH WORD TABLE
1430 LOOP3 LDA BUFFER,X
1440 CMP TABLE,?
1450 BNE NOMATCH ; DOESN'T MATCH
1460 INX ; IT MATCHED
1470 IN? ; TRY NEXT CHARACTER
1480 CPX 04
1490 BNE L0OP3
1500 JMP FOUND ; FOUND IT!
1510 NOMATCH INC COUNT ; INCREMENT WORD COUNT
1520 LDA COUNT
1530 CMP TABLEN z ANY MORE WORDS TO CHECKPR1NT
1540 BEQ NOTFOUND ;NO
1550 ASL A ; BUMP COUNTER BY 4 TIMES
1560 ASL A ; WORD NUMBER •
3) If two words are found, the first is a
verb and the second a noun e.g. TAKE
SWORD, EAT SK AK E.
Extract the verb and move it to a
buffer starting at VERB and put it's
length into VERBLEN.
Similarly move the noun to a buffer
starting at NOUN and its length into
NOUN LEN.
Consider this simple method of
text compression. If you use just 32
characters, you only need live bits to
save each character. This being the
case, you can save three characters in
two bytes giving 33% saving in RAM.
Consider this example:
Character I — %000IIIII
Character 2 — %00010101
Character 3 — %%0001 lol l
'I his compresses to:
Byte I I 111101 and Byte 2:
%0I110110
As you can see, character I now
YOUR COMMODORE november 1986:88
occupies the top five bits of byte
Character two occupies the bottom
three bits of byte I and the top two bits
of byte 2. Character three occupies bits
I to bit 5 inclusive of byte 2. Bit 0 to
byte 2 is set to zero.
Your task is to:
I) Develop an algorithm which
performs the compression.
2) Write a routine to do this job using
so far as possible logical shifts and rolls
and boolean instructions such as OR
and AND.