Homework Help is Here – Start Your Trial Now!
Engineering
Computer Engineering
To add a pair of two-digit (1.e., single-byte) BCD values together, you would use the following sequence: mov( bcd_1, al ); add( bcd_2, al ); daa(); // Assume that bcd 1 and bcd 2 both contain // valid BCD values. The first two instructions above add the 2-byte values together using standard binary arithmetic. This may not produce a correct BCD result. For example, if bcd_1 contains $9 and bcd_2 contains $1, then the first two instruc- tions above will produce the binary sum $A instead of the correct BCD result $10. The daa instruction corrects this invalid result. It checks to see if there was a carry out of the low-order BCD digit and adjusts the value (by adding 6 to it) if there was an overflow. After adjusting for overflow out of the L.O. digit, the daa instruction repeats this process for the H.O. digit. daa sets the carry flag if there was a (decimal) carry out of the H.O. digit of the operation. The daa instruction operates only on the AL register. It will not adjust (properly) for a decimal addition if you attempt to add a value to AX, EAX, or other register. Specifically note that daa limits you to adding two decimal digits (a single byte) at a time. This means that for the purposes of computing decimal sums, you have to treat the 80x86 as though it were an 8-bit processor, capable of adding only 8 bits at a time. If you wish to add more than two digits together, you must treat this as a multiprecision operation. For example, to any

To add a pair of two-digit (1.e., single-byte) BCD values together, you would use the following sequence: mov( bcd_1, al ); add( bcd_2, al ); daa(); // Assume that bcd 1 and bcd 2 both contain // valid BCD values. The first two instructions above add the 2-byte values together using standard binary arithmetic. This may not produce a correct BCD result. For example, if bcd_1 contains $9 and bcd_2 contains $1, then the first two instruc- tions above will produce the binary sum $A instead of the correct BCD result $10. The daa instruction corrects this invalid result. It checks to see if there was a carry out of the low-order BCD digit and adjusts the value (by adding 6 to it) if there was an overflow. After adjusting for overflow out of the L.O. digit, the daa instruction repeats this process for the H.O. digit. daa sets the carry flag if there was a (decimal) carry out of the H.O. digit of the operation. The daa instruction operates only on the AL register. It will not adjust (properly) for a decimal addition if you attempt to add a value to AX, EAX, or other register. Specifically note that daa limits you to adding two decimal digits (a single byte) at a time. This means that for the purposes of computing decimal sums, you have to treat the 80x86 as though it were an 8-bit processor, capable of adding only 8 bits at a time. If you wish to add more than two digits together, you must treat this as a multiprecision operation. For example, to any

Computer Networking: A Top-Down Approach (7th Edition)
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
See similar textbooks
icon
Related questions
Question
program
To add a pair of two-digit (i.e., single-byte) BCD values together, you would use the following sequence: mov( bcd_1, al ); add( bcd_2, al ); daa(); // Assume that bcd 1 and bcd 2 both contain // valid BCD values. The first two instructions above add the 2-byte values together using standard binary arithmetic. This may not produce a correct BCD result. For example, if bcd_1 contains $9 and bcd 2 contains $1, then the first two instruc- tions above will produce the binary sum $A instead of the correct BCD result $10. The daa instruction corrects this invalid result. It checks to see if there was a carry out of the low-order BCD digit and adjusts the value (by adding 6 to it) if there was an overflow. After adjusting for overflow out of the L.O. digit, the daa instruction repeats this process for the H.O. digit. daa sets the carry flag if there was a (decimal) carry out of the H.O. digit of the operation. The daa instruction operates only on the AL register. It will not adjust (properly) for a decimal addition if you attempt to add a value to AX, EAX, or any other register. Specifically note that daa limits you to adding two decimal digits (a single byte) at a time. This means that for the purposes of computing decimal sums, you have to treat the 80x86 as though it were an 8-bit processor, capable of adding only 8 bits at a time. If you wish to add more than two digits together, you must treat this as a multiprecision operation. For example, to add four decimal digits together (using daa), vou must execute a seguence
Transcribed Image Text:To add a pair of two-digit (i.e., single-byte) BCD values together, you would use the following sequence: mov( bcd_1, al ); add( bcd_2, al ); daa(); // Assume that bcd 1 and bcd 2 both contain // valid BCD values. The first two instructions above add the 2-byte values together using standard binary arithmetic. This may not produce a correct BCD result. For example, if bcd_1 contains $9 and bcd 2 contains $1, then the first two instruc- tions above will produce the binary sum $A instead of the correct BCD result $10. The daa instruction corrects this invalid result. It checks to see if there was a carry out of the low-order BCD digit and adjusts the value (by adding 6 to it) if there was an overflow. After adjusting for overflow out of the L.O. digit, the daa instruction repeats this process for the H.O. digit. daa sets the carry flag if there was a (decimal) carry out of the H.O. digit of the operation. The daa instruction operates only on the AL register. It will not adjust (properly) for a decimal addition if you attempt to add a value to AX, EAX, or any other register. Specifically note that daa limits you to adding two decimal digits (a single byte) at a time. This means that for the purposes of computing decimal sums, you have to treat the 80x86 as though it were an 8-bit processor, capable of adding only 8 bits at a time. If you wish to add more than two digits together, you must treat this as a multiprecision operation. For example, to add four decimal digits together (using daa), vou must execute a seguence
Expert Solution
steps

Step by step

Solved in 2 steps

SEE SOLUTIONCheck out a sample Q&A here
Blurred answer
Recommended textbooks for you
Computer Networking: A Top-Down Approach (7th Edi…
Computer Networking: A Top-Down Approach (7th Edi…
Computer Engineering
ISBN:
9780133594140
Author:
James Kurose, Keith Ross
Publisher:
PEARSON
Computer Organization and Design MIPS Edition, Fi…
Computer Organization and Design MIPS Edition, Fi…
Computer Engineering
ISBN:
9780124077263
Author:
David A. Patterson, John L. Hennessy
Publisher:
Elsevier Science
Network+ Guide to Networks (MindTap Course List)
Network+ Guide to Networks (MindTap Course List)
Computer Engineering
ISBN:
9781337569330
Author:
Jill West, Tamara Dean, Jean Andrews
Publisher:
Cengage Learning
Concepts of Database Management
Concepts of Database Management
Computer Engineering
ISBN:
9781337093422
Author:
Joy L. Starks, Philip J. Pratt, Mary Z. Last
Publisher:
Cengage Learning
Prelude to Programming
Prelude to Programming
Computer Engineering
ISBN:
9780133750423
Author:
VENIT, Stewart
Publisher:
Pearson Education
Sc Business Data Communications and Networking, T…
Sc Business Data Communications and Networking, T…
Computer Engineering
ISBN:
9781119368830
Author:
FITZGERALD
Publisher:
WILEY
SEE MORE TEXTBOOKS