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Add two 4-digit BCD numbers

Published on Nov 18 2009 // Trainees

Statement: Add two 4 digit BCD numbers in HL and DE register pairs and store result in memory locations, 2300H and 2301H. Ignore carry after 16 bit.

Sample Problem:

(HL) =3629

(DE) =4738

Step 1 : 29 + 38 = 61 and auxiliary carry flag = 1

:.add 06

61 + 06 = 67

Step 2 :  36 + 47 + 0 (carry of LSB) = 7D

Lower nibble of addition is greater than 9, so add 6.

7D + 06 = 83

Result = 8367

Source program :

  • MOV A, L : Get lower 2 digits of no. 1
  • ADD E : Add two lower digits
  • DAA : Adjust result to valid BCD
  • STA 2300H : Store partial result
  • MOV A, H : Get most significant 2 digits of number
  • ADC D : Add two most significant digits
  • DAA : Adjust result to valid BCD
  • STA 2301H : Store partial result
  • HLT : Terminate program execution.

 

Flowchart for Program

46-Add two 4-digit BCD numbers

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