Programming task examples, Table 2, Bubble listing – Zilog Z08470 User Manual
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UM008007-0715
Programming Task Examples
Z80 CPU
User Manual
29
SBC
A, (HL)
;SUBTRACT (HL) FROM ACC
DAA
;ADJUST RESULT TO DECIMAL CODED VALUE
LD
(HL), A
;STORE RESULT
INC
HL
;ADVANCE MEMORY POINTERS
INC
DE
DJNZ
SUBDEC–$
;DECREMENT B AND GO TO SUBDEC
;IF B
;NOT ZERO, OTHERWISE FALL
;THROUGH
Seventeen bytes are required for this operation.
Programming Task Examples
As indicated in Table 2, this example program sorts an array of numbers to ascending
order, using a standard exchange sorting algorithm. These numbers range from 0 to 255.
Table 2. Bubble Listing
Location
Object
Code
Statement
Source Statement
1
;
standard exchange (bubble) sort routine
2
;
3
;
at entry:
hl contains address of data
c contains number of elements to be sorted
(1 < c < 256)
4
5
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