1. Assembly Language Lecture 04-06 BY SHERY KHAN sherykhan@gmail.com
Review By
Sultan Fahad
April

2. LACUNY Web Roundtable galina.letnikova@lehman.cuny.edu
Agenda
To day we learn about
Recap & Exercise (Page 15)
Data Declaration (Page 17)
Direct Addressing (page 17)
Size Mismatch Errors (page 21)
Register Indirect Addressing (page 22)
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April

3. LACUNY Web Roundtable galina.letnikova@lehman.cuny.edu
RECAP & EXERCISE
Last Lecture we can discuss the Few Important Topics Now on the basis of previous knowledge we can Solve the Exercise
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April

4. LACUNY Web Roundtable galina.letnikova@lehman.cuny.edu
Exercise How the Processor uses the Address Bus ,Data bus and control Bus?
Processor Execute Operation and memory contain data element Memory is a Dump Device in which Data resides Key point is that Processor want to read or write Data so for reading data or writing purposes are achieved by Address bus & data Bus & Control Bus Address bus is Used When Processor Want to Certain read or write operation. Data Bus is Used to move data form Memory to Processor in Read Operation & Processor to Memory For Write Operation. Control BUS is independent lines used to inform Memory about Certain operation
October 21, 2005
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April

5. EXERCISE Qno2 Which of the Following are Uni & Bi Directional
Address Bus Is Uni Directional because Address Always Travel From Processor to Memory & Memory Cannot Predict which Element the Processor want to read or Write
DATA BUS: data Travel From Both processor to memory& vice versa So data Bus is Bi Directional
Control Bus Is Bi directional
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6. What is The Size of the Accumulator of 64 bit Processor?
The Size of Accumulator of 64 bit processor is 64 bit According to defination
“ the Word size of processor is defined by the width of accumulator”
October 21, 2005
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April

7. How many Instruction Classified into groups?
There are Four Categories of Instructions.
Data Movement Instruction
Arithmetic Logic instruction
Program Control Instruction
Special Instructions
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8. A combination of 8 bit are Byte what is name of Four Bit & 16 bit??
Four BITS: are called as NIBBLE
Four Bytes : Are Called double Word (32bit)
16 Bits : are called word (2 byte long)
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9. What is Maximum Memory 8088 can access??
The 8088 can Allow Whole MEGA BYTE
Which can be Accessed with 20 bits
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10. LACUNY Web Roundtable galina.letnikova@lehman.cuny.edu
List the 14 register of 8088 ?
HERE TO New the Register the Afd View
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11. What is Difference Little Endean & Big Endian
Little Endian: Big Endian:
Least Significant Most Significant
More Significant Less Significant
Most Significant Least Significant
For e.g For e.g
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12. Which Format was Used by INTEL 8088
Little Endian Order is used By Intel8088
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13. LACUNY Web Roundtable galina.letnikova@lehman.cuny.edu
Give the Value of Zero flag carry flag sign flag and overflow flag after each of the Following instructions mov ax 0x mov bx 0x0FFF
add ax,0xEDAB
Zero FLAG:0
CF:0
SF:1
OF:0
Add ax,bx
ZF:0
SF:0
oF:0
Add bx,0xf001
ZF:0, CF:1 SF:0 OF:0
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14. LACUNY Web Roundtable galina.letnikova@lehman.cuny.edu
13. For each of the following words identify the byte that is stored at lower memory address and the byte that is stored at higher memory address in a little endian computer.
a b. ABFC c. B100 d. B800
FEW SLIDE SHOW WE DISCUSS THE LITTLE ENDIAN
Above the 1234 Followed the Definition So this Is our desired Result
1234
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15. LACUNY Web Roundtable galina.letnikova@lehman.cuny.edu
15. What is the offset at which the first executable instruction of a COM file must be placed?
The First Instruction of COM File Must be Offset at 0x0100(decimal 255) as required
What is the difference between an instruction mnemonic and its opcode?
Opcode
Short for operational code, it is a number that determines the computer instruction to be
executed. (machine language representation of an instruction
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April

16. What flags are defined in the 8088 FLAGS register
What flags are defined in the 8088 FLAGS register? Describe the function of the zero flag, the carry flag, the sign flag, and the overflow flag. Zero flag?????
The Zero flag is set if the last mathematical or logical instruction has produced a zero in
its destination.
Carry flag
When two 16bit numbers are added the answer can be 17 bits long or when two 8bit
numbers are added the answer can be 9 bits long. This extra bit that won’t fit in the target
register is placed in the carry flag where it can be used and tested.
Sign flag
A signed number is represented in its two’s complement form in the computer. The most
significant bit (MSB) of a negative number in this representation is 1 and for a positive
number it is zero. The sign bit of the last mathematical or logical operation’s destination
is copied into the sign flag.
Overflow flag
The overflow flag is set during signed arithmetic, e.g. addition or subtraction, when the
sign of the destination changes unexpectedly. The actual process sets the overflow flag
whenever the carry into the MSB is different from the carry out of the MSB.

17. What are the contents of memory locations 200, 201, 202, and 203 if the word 1234 is stored at offset 200 and the word 5678 is stored at offset 202?
In Little Endean, least significant byte is stored first at lower addresses; most significant
byte is stored after it. Like for example the number 0x1234 is stored at memory address
0x123 then it will appear like as below:
Address Contents …
0x123 34
0x124 12
Do try it for the given memory addresses with given numbers.

18. Why was segmentation originally introduced in 8088 architecture?
Four windows of 64K
Code window
Data window
Stack window
The segmented memory model allows multiple functional windows into
the main memory, a code window, a data window etc. The processor sees
code from the code window and data from the data window. The size of
one window is restricted to 64K software fits in just one such
window. It sees code, data, and stack from this one window, so
downward compatibility is attained.

19. What are the first and the last physical memory addresses accessible using the following segment values?
First 0x0000 and last 0xFFFF
First physical address Last physical address
a. 1000
0x x10000
+0x x0FFFF
=0x =0x1FFFF
b. 0FFF
0x0FFF0 0x0FFF0
+0x x0FFFF
=0x0FFF0 =0x1FFEF
1002
0x x10020
+0x x0FFFF
=0x =0x2001F
d. 0001
0x x00010
=0x =0x1000F
E000
0xE xE0000
=0xE =0xEFFFF

20. Why a segment start cannot start from the physical address 55555??.
For any segment base address, segment first physical address will have 0 in the least
significant position in hexadecimal format.
Let say,our Segment base =0x1234, and we calculate segment first physical address as
0x12340 <- 0x x00000 (Segment First Address)
Thusall segments starting physical address has 0 at its least significant position. In case
of as segment first physical address there in no 0 at least significant positions so
this cannot be a segment starting physical address.

21. Q21 Write a program in assembly language that Calculate the Square ?
[org 0x0100]
Mov ax, 6
Add ax, 6
Mov ax, 0x4c00
Int 0x21
April

22. Table of Hexa To Deci
October 21, 2005

23. First physical address = 00000 + 00000 = 00000
What are the first and the last physical memory addresses accessible using the following segment values? (2 mark each)
0000
FFFF
Answer: a)
First physical address = = 00000
Last physical address = FFFF = 0FFFF b)
First physical address = FFFF = FFFF0
Last physical address = FFFF0 + 0FFFF = 10FFEF = 0FFEF (wraparound)
26 April 2013
Shery khan

24. TODAY LECTURE 05 DATA DECLARATION:
IMMEDIATE OPERANDS: In our previous Programs We use a Immediate operand but in Meaningful Programs we use data from Memory instead of Constant because constant cannot change Constant cannot appear as destination operand which is Ilegal if we place it as Destination we know that
operation destination, source
operation destination
operation source
operation
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25. LACUNY Web Roundtable galina.letnikova@lehman.cuny.edu
DATA DECLARATION:
Only Register or data Can be placed in memory can be changed
So real data is one stored in memory with
Few constant so there is Mechanism which is used And is Called Data Declaration
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26. LACUNY Web Roundtable galina.letnikova@lehman.cuny.edu
DATA DECLARATION:
To Declare a part of our program as holding data instead of instruction we need a Special Directives which are Following
DEFINE BYTE: (db) I byte
DEFINE WORD :(dw) 16 bits(2 byte)
Db: reserve one single byte cell in memory dw:reserve whole 16 bits instead of Byte
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