Lab 1 for Assembly x86 processors

1. Assembly Language - Lab (1)
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2. Agenda
 Logistics
 CourseSites
 Introduction
 Data Representation
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3. Logistics
Text Book
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4. Evaluation
Year Work (25 Marks)
Assignments
Lab work
Project
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5. Assignments
Assignments are INDIVIDUAL work.
Never share code/solution.
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6. Honor Code
My answers will be my own work.
I will not make solutions available or seen by anyone else.
Violations:
Plagiarism (copy all or part of it)
Representing the work of another as one’s own work
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7. CourseSites
https://www.coursesites.com/

8. Introduction
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9. Why Assembly?
All high-level languages are an abstraction how the
computer works, abstraction means the programmer
don’t have to worry about the computer details.
Assembly is a really good way to understand what is the
computer doing because you control exactly what
happens at each step.
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10. Why Assembly?
Assembly language gives the programmer the ability to
perform technical tasks that would be difficult in
high‐level languages including total control on the
machine.
Software written in assembly language runs faster than
the same one written in high‐level language and takes
less amount of memory if the programmer
well‐optimized the assembly program code.
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11. Why Assembly?
Learning assembly language gives deep understanding of
the computer’s organization and architecture and how
programs run, since it is necessary to know the
architecture of the processor or controller in order to
write assembly code.
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12. What can we do using Assembly?
Device Driver:
is a program that controls a particular type of device
that is attached to your computer.
Only assembly and C can implement this since they give
you a full control over the hardware.
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13. What can we do using Assembly?
Virus Programming:
a simple program that infects other programs:
1. by injecting itself in the end of the program
2. by applying changes to file header and RPT
(Relocation pointer table) to execute the virus first and
execute the host program
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14. What can we do using Assembly?
Reverse Engineering:
is the process of reversing code from a machine
language (binary code) using disassembler, then we
can:
analyze and understand the program
changing features in program (ex: cracking the
program)
debugging program
without having the source code of the program
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15. What can we do using Assembly?
Embedded Software:
a software written to control a machine or device, that
is specialized for a certain device, and has time and
memory constraints, such as telephone, automobile,
air-condition control system, video cards, sound cards,
printers, etc.
Since assembly is the fastest language and takes the
lowest memory, it is the best for embedded system.
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16. Machine Language VS Assembly
Language
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17. Machine Language
Computers work only with 0’s and 1’s.
Every program instruction or data element must be in
binary to be manipulated by computer machine.
Therefore, any program understood by machine has to
be written in machine language, however machine
language is too hard to write and maintain.
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18. Machine Language
Machine Language is a set of binary codes (0’s and 1’s)
that represent instructions of a specific machine. It is
machine‐dependent.
For example, the instruction
8B D8
means copy content from AX register to BX register.
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19. Assembly Language
Assembly language is developed to make programming
easier than programming using machine language.
Assembly language is a set of mnemonics (symbols) for
machine code instructions plus other features that make
programming easier.
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20. Assembly Language
To run program written in assembly language, we should
have a converter (or translator) which converts these
labels and mnemonics to their corresponding machine
codes in 0’s and 1’s. This converter is called assembler.
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Machine CodeAssemblerAssembly Code

21. Assembly Language
Assembly Language is a low-level (machine‐level)
programming language that uses mnemonics instead of
numeric codes to simplify programming.
For example, the instruction
mov BX, AX
means copy content from AX register to BX register.
Each statement in assembly code has a one-to-one
relationship with machine language instructions, in other
words each statement corresponds to a single machine
code instruction.
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22. Assembly Language
Each assembly language is machine‐dependent which
means it is specific to a particular computer architecture.
In contrast to most high-level programming languages,
which are generally portable across multiple systems.
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23. Assembly Language
We’ll use Irvine Library with Visual Studio to write our
Assembly code.
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24. Data Representation
Numbering Systems Conversions
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25. Numbering Systems
Data Representation
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System Base Possible Digits
Binary 2 0 and 1
Octal 8
0, 1, 2, 3, 4, 5, 6, and
7
Decimal 10
0, 1, 2, 3, 4, 5, 6, 7,
8, and 9
Hexadecimal 16
0, 1, 2, 3, 4, 5, 6, 7,
8, 9, A, B, C, D, E,
and F

26. Converting from unsigned binary to
decimal
 1101102
1x25 + 1x24 + 0x23 + 1x22 + 1x21 + 0x20
= 1x32 + 1x16 + 0 + 1x4 + 1x2 + 0
= 32 + 16 + 4 + 2
= 5410
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27. Converting from unsigned binary to
decimal
 111100002
1x27 + 1x26 + 1x25 + 1x24 + 0x23 + 0x22 + 0x21 + 0x20
= 1x128 + 1x64 + 1x32 + 1x16 + 0 + 0 + 0 + 0
= 128 + 64 + 32 + 16
= 24010
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28. Converting from signed binary to decimal
 001010102
0x26 + 1x25 + 0x24 + 1x23 + 0x22 + 1x21 + 0x20
= 0 + 1x32 + 0 + 1x8 + 0 + 1x2 + 0
= 32 + 8 + 2
= +4210
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1st bit is 0, then the
number is positive

29. Converting from signed binary to decimal
 111100002
 Get the 2’s complement
2’s complement = 1’s complement + 1
00010000 = 00001111 + 1
 Convert the 2’s complement to decimal and attach the
negative sign
0x27 + 0x26 + 0x25 + 1x24 + 0x23 + 0x22 + 0x21 + 0x20
= 0 + 0 + 0 + 16 + 0 + 0 + 0 + 0
= 16
= -1610
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1st bit is 1, then the number
is negative

30. • 2310
= 101112
Division Quotient Remainder
23 / 2 =
11.5
11 1
11 / 2 = 5.5 5 1
5 / 2 = 2.5 2 1
2 / 2 = 1 1 0
1 / 2 = 0.5 0 1
10111
Stop when
quotient = 0
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Converting from unsigned decimal to
binary

31. • -2310
a. Convert the decimal value into binary
Division Quotient Remainder
23 / 2 = 11.5 11 1
11 / 2 = 5.5 5 1
5 / 2 = 2.5 2 1
2 / 2 = 1 1 0
1 / 2 = 0.5 0 1
10111
Stop when
quotient = 0
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Converting from signed decimal to binary

32. b. If the original number is negative, then get the 2’s
complement of the result
Result = 101112 = 000101112
2’s complement = 1’s complement + 1
= 11101000 + 1
= 111010012
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Converting from signed decimal to binary

33. Converting from unsigned binary to
hexadecimal
 Each hexadecimal digit corresponds to 4 binary bits.
 0101 10112
 Convert each 4 bits to a hexadecimal digit
=5B16
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0 x 23 + 1 x 22 + 0 x 21 + 1 x 20 1 x 23 + 0 x 22 + 1 x 21 + 1 x 20
0 + 1 x 4 + 0 + 1 x 1 1 x 8 + 0 + 1 x 2 + 1 x 1
4 + 1 8 + 2 + 1
5 11
5 B

34. • A616
a. Convert each hexadecimal digit to 4 bits
= 101001102
A = 10
Division Quotient Remainder
10 / 2 = 5 5 0
5 / 2 = 2.5 2 1
2 / 2 = 1 1 0
1 / 2 = 0.5 0 1
1010
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Division Quotient Remainder
6 / 2 = 3 3 0
3 / 2 = 1.5 1 1
1 / 2 = 0.5 0 1
… … 0
0110
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Converting from unsigned
hexadecimal to binary

35. • Addition and Subtraction
• 1’s Complement
• Covert each 1 to 0, and each 0 to 1.
1’s complement of 10110102 = 01001012
• 2’s Complement
• Add 1 to the 1’s complement.
2’s complement of 10110102 = 01001102
• 2’s complement is used in representing negative
numbers.
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Numbering Systems

36. • Binary Operations
• 11001 + 10101 = 101110
• The operation’s result does not fit in 5 bits, so the
underlined 1 in the previous number is called a carry.
• 11001 – 10101 = 11001 + 01011 = 00100 with carry = 1
• Carry = 1 in subtraction means that the result is positive with no
borrow.
• 10101 – 11001 = 10101 + 00111 = 11100 with carry = 0
• Carry = 0 in subtraction means that the result is negative with
borrow.
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2’s complement
of 10101
2’s complement
of 11001
Numbering Systems

37. • Hexadecimal Operations
• 23D9 + 94BE
9 + 14 = 23 23 – 16 = 7 with carry
13 + 11 + 1 = 25 25 – 16 = 9 with carry
3 + 4 + 1 = 8
2 + 9 = B
= B897
• 59F – 2B8
15 – 8 = 7
(9 + 16) – 11 = 14 (E)
4 – 2 = 2
= 2E7
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Numbering Systems

38. Additional Examples
1. 000101101010011110010100)2 = )16
2. 1234)16 = )10
3. 422)10 = )16
4. 3628286A + 4245584B )16 = )16
5. C675 – A247)16 = )16
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39. • All data stored in memory is numeric.
• Characters are stored by using a character code that maps
numbers to characters.
• One of the most common character codes is known as ASCII
(American Standard Code for Information Interchange). It
uses 1 byte (8 bits) to encode characters. Therefore, it is
limited to encode only 256 (28) characters.
• A new and more complete code that is supplanting ASCII is
Unicode. It uses 2 bytes (16 bits) to encode characters.
Therefore, it is capable to encode 65536 (216) characters.
ASCII Code
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40. Questions !?
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41. Thank you 
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