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Assembly Language - Lab (1)

Agenda Logistics CourseSites Introduction Data Representation

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Logistics

Text Book

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Evaluation

Year Work (25 Marks)Assignments Lab workProject

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AssignmentsAssignments are INDIVIDUAL work. Never share code/solution.

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Honor CodeMy 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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CourseSiteshttps://www.coursesites.com/

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Introduction

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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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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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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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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What can we do using Assembly?Virus Programming:

a simple program that infects other programs:1. by injecting itself in the end of the program2. 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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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 programchanging features in program (ex: cracking the

program)debugging program

without having the source code of the program

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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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Machine Language VS Assembly Language

Machine LanguageComputers 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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Machine LanguageMachine 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 instruction8B D8

means copy content from AX register to BX register.

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Assembly LanguageAssembly 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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Assembly LanguageTo 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

Assembly LanguageAssembly Language is a low-level (machine level) programming ‐

language that uses mnemonics instead of numeric codes to simplify programming.

For example, the instructionmov 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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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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Assembly LanguageWe’ll use Irvine Library with Visual Studio to write our

Assembly code.

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Data Representation Numbering Systems Conversions

Numbering SystemsData 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 160, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E,

and F

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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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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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

Converting from signed binary to decimal

111100002

Get the 2’s complement2’s complement = 1’s complement + 100010000 = 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

• 2310

= 101112

Division Quotient Remainder23 / 2 =

11.5 11 1

11 / 2 = 5.5 5 15 / 2 = 2.5 2 12 / 2 = 1 1 0

1 / 2 = 0.5 0 1

10111

Stop when quotient = 0

31Converting from unsigned decimal to binary

• -2310

a. Convert the decimal value into binaryDivision 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

b. If the original number is negative, then get the 2’s complement of the resultResult = 101112 = 000101112

2’s complement = 1’s complement + 1 = 11101000 + 1 = 111010012

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Converting from signed decimal to binary

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

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• A616

a. Convert each hexadecimal digit to 4 bits

= 101001102

A = 10Division Quotient Remainder

10 / 2 = 5 5 05 / 2 = 2.5 2 12 / 2 = 1 1 0

1 / 2 = 0.5 0 1

1010

6Division Quotient Remainder

6 / 2 = 3 3 03 / 2 = 1.5 1 11 / 2 = 0.5 0 1

… … 0

0110

Converting from unsigned hexadecimal to binary

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• 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.

Numbering Systems

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• 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.

2’s complement of 10101

2’s complement of 11001

Numbering Systems

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• Hexadecimal Operations• 23D9 + 94BE

9 + 14 = 23 23 – 16 = 7 with carry13 + 11 + 1 = 25 25 – 16 = 9 with carry3 + 4 + 1 = 82 + 9 = B= B897

• 59F – 2B815 – 8 = 7(9 + 16) – 11 = 14 (E)4 – 2 = 2= 2E7

Numbering Systems

Additional Examples1. 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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• 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 Code40

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Questions !?

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Thank you