ZiLOG Z80-CPU Technical Manual page 73

01/22/76
11: 14:37
BUBBLE LISTING PAGE 1
LOC OBJCODE STMT SOURCE STATEMENT
1
***
STANDARD EXCHANGE (BUBBLE) SORT ROUTINE
***
2
3 AT ENTRY: HL CONTAINS ADDRESS OF DATA
4 C CONTAINS NUMBER OF ELEMENTS TO BE SORTED
5
(l<C<256)
6
7 AT EXIT: DATA SORTED IN ASCENDING ORDER
8
9 USE OF REGISTERS
10
11 REGISTER CONTENTS
12
13
A TEMPORARY STORAGE FOR CALCULATIONS
14 B COUNTER FOR DATA ARRAY
15 C LENGTH OF DATA ARRAY
16 D
FIRST ELEMENT IN COMPARISON
17 E SECOND ELEMENT IN COMPARISON
18 H
FLAG TO INDICATE EXCHANGE
19 L UNUSED
20 IX
POINTER INTO DATA ARRAY
21 IY UNUSED
22
0000 222600 23 SORT: LD (DATA), HL
; SAVE DATA ADDRESS
0003
CB84 24 LOOP: RES FLAG,H ; INITIALIZE EXCHANGE FLAG
0005 41 25
LD B,C ; INITIALIZE LENGTH COUNTER
0006
05
26 DEC B ; ADJUST FOR TESTING
0007 DD2A2600 27
LD IX, (DATA) ; INITIALIZE ARRAY POINTER
OOOB
DD7EOO
28 NEXT: LD A, (IX) ; FIRST ELEMENT IN COMPARISON
OOOE 57 29 LD D,A ; TEMPORARY STORAGE FOR ELEMENT
OOOF DD5E01 30 LD E, (IX+l) ; SECOND ELEMENT IN COMPARISON
0012 93 31 SUB E ; COMPARISON FIRST TO SECOND
0013 3008 32 JR NC, NOEX-$
; IF FIRST> SECOND, NO JUMP
0015 DD7300 33
LD (IX), E ; EXCHANGE ARRAY ELEMENTS
0018 DD7201 34 LD (IX+1), D
001B CBC4
35 SET FLAG,H ; RECORD EXCHANGE OCCURRED
OOlD DD23 36 NOEX: INC IX ; POINT TO NEXT DATA ELEMENT
001F lOEA 37 DJNZ
NEXT-$ ; COUNT NUMBER OF COMPARISONS
38 ; REPEAT IF MORE DATA PAIRS
0021 CB44
39 BIT FLAG,H ; DETERMINE IF EXCHANGE OCCURRED
0023 20DE
40 JR NZ,LOOP-$ ; CONTINUE IF DATA UNSORTED
0025 C9 41
RET ; OTHERWISE, EXIT
42
0026 43
FLAG:
EQU
0 ; DESIGNATION OF FLAG BIT
0026 44 DATA:
DEFS 2 ; STORAGE FOR DATA ADDRESS
45 END
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