Binary coded decimal (BCD) is a way to express each of the decimal digits with a binary code. This means that each decimal digit, 0 through 9, is represented by a binary code of four bits.
Eg: 98 => 10011000
Unpacking the BCD number is separating each BCD digit.
Eg: 98 can be separated as 09 and 08. So we can say 10011000 [98] is packed and 00001001 [09] & 00001000 [08] are unpacked.
You might like to go through Step by step Process to add two packed BCD Numbers
Assembly language program to unpack the packed BCD number
// Manually store the packed BCD number [eg: 98 in this case] in the memory locations 3000H
// Store the result i.e, the unpacked numbers in the memory locations 3001H and 3002H
// For this Example result will be 09 and 08
// 3000<-09, 3001<-08
#ORG 0000H
#BEGIN 0000H
LDA 3000H //Get the packed BCD number from the memory
MOV B,A
MVI C,04
ANI F0 // A = 90H
L1: RRC // Need to be rotated right for 4 times to get A = 09H
DCR C
JNZ L1
STA 3001
MOV A,B
ANI 0F // A = 08H
STA 3002
HLT
#ORG 3000H
#DB 98H
Now when you would run the program it would give you the memory locations with the following values:
Note: The above Hex codes have been assembled and simulated on Jubin’s 8085 Simulator.
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