ZiLOG Z80 Handbook page 187

Table 13-1. Five-Character String Comparison
Character
Total of
String ASCII
Bytes
WHITE 57H, 48, 49, 54, 45
181H
GREEN 47, 52, 45, 45, 4E
171 H
BROWN 42, 52, 4F, 57, 4E 17EH
MAUVE
4D,
41,
55,
56, 45
17EH
An implementation of a search based on this simple hash is shown
in the following code.
HASHSR LD IX,CHAR START OF 5-CHAR KEY
LD A,(IX + 1) LOAD KEY CHARACTERS
ADD A,(IX+2)
ADD A,( IX+3)
ADD A ,(IX+4)
LD D,A SAVE IN D
LD HL, STRING START OF STRING
LD BC , 60 60 BYTES = DONE
LOOP LD A,(CHAR + O) FIRST CHARACTER
CPIR SEARCH FOR 1ST CHAR
JP NZ,NFND GO IF NOT FOUND
SECLVL PUSH HL SAVE POINTER
POP IX POINT TO 2ND CHAR
LD A,(IX)
ADD A ,( IX+ 1)
ADD A ,( IX+2)
ADD A,( IX+3) COMPUTE HASH
CP D COMPARE TO KEY HASH
JP NZ ,LOOP GO IF NO MATCH
MAYBE LD IY,CHAR + 1 POINT TO 2ND CHAR OF KEY
LD A,(IX)
CP A,(IY)
JP NZ , LOOP GO IF NO MATCH 2ND CHAR
LD A,(IX+1)
CP A,(IY+1)
JP NZ , LOOP GO IF NO MATCH 3RD CHAR
LD A,(IX+2)
CP A,(IY+2)
JP NZ,LOOP GO IF NO MATCH 4TH CHAR
LD A,(IX+3)
CP A,(IY+3)
JP NZ , LOOP GO IF NO MATCH 5TH CHAR
FOUND FOUND!
If a match is found on the first character , SECLVL is entered. A
hash is then computed for the remaining four characters of the
string and compared to the precomputed key hash in D. If there is
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