Chapt 01

AAsssseemmbbllyy LLaanngguuaaggee ffoorr IInntteell--BBaasseedd
CCoommppuutteerrss,, 55tthh EEddiittiioonn
Kip Irvine
Chapter 1: Basic Concepts
Slides prepared by the author
Revision date: June 3, 2006
(c) Pearson Education, 2006-2007. All rights reserved. You may modify and copy this slide show for your personal use,
or for use in the classroom, as long as this copyright statement, the author's name, and the title are not changed.

OObbjjeeccttiivveess
• Understand common applications of assembly
language
• Understand what an assembler does
• Understand hardware and software requirements for
the book
• Know the basic history of PC Assemblers
• Differentiate between protected mode and real-address
mode
• Learn basic principles of computer architecture as
applied to the Intel IA-32 processor family
Irvine, Kip R. Assembly Language for Intel-Based Computers 5/e, 2007. Web site Examples 2

OObbjjeeccttiivveess ((ccoonnttiinnuuee))
• Learn how to recognize and convert boolean and
hexadecimal integers
• Perform binary addition and subtraction
• Understand basic boolean operations
• Differentiate between signed and unsigned binary
integers
• Understand ASCII character representation

CChhaapptteerr OOvveerrvviieeww
• Welcome to Assembly Language
• Virtual Machine Concept
• Data Representation
• Boolean Operations

WWeellccoommee ttoo AAsssseemmbbllyy LLaanngguuaaggee
• Some Good Questions to Ask
• Assembly Language Applications

QQuueessttiioonnss ttoo AAsskk
• Why am I learning Assembly Language?
• What background should I have?
• What is an assembler?
• What hardware/software do I need?
• What types of programs will I create?
• What do I get with this book?
• What will I learn?

WWeellccoommee ttoo AAsssseemmbbllyy LLaanngguuaaggee ((ccoonntt))
• How does assembly language (AL) relate to machine
language?
• How do C++ and Java relate to AL?
• Is AL portable?
• Why learn AL?

AAsssseemmbbllyy LLaanngguuaaggee AApppplliiccaattiioonnss
• Some representative types of applications:
• Business application for single platform
• Hardware device driver
• Business application for multiple platforms
• Embedded systems & computer games
(see next panel)

CCoommppaarriinngg AASSMM ttoo HHiigghh--LLeevveell LLaanngguuaaggeess

WWhhaatt''ss NNeexxtt

VViirrttuuaall MMaacchhiinnee CCoonncceepptt
• Virtual Machines
• Specific Machine Levels

VViirrttuuaall MMaacchhiinneess
• Tanenbaum: Virtual machine concept
• Programming Language analogy:
• Each computer has a native machine language (language
L0) that runs directly on its hardware
• A more human-friendly language is usually constructed
above machine language, called Language L1
• Programs written in L1 can run two different ways:
• Interpretation – L0 program interprets and executes L1
instructions one by one
• Translation – L1 program is completely translated into an L0
program, which then runs on the computer hardware

TTrraannssllaattiinngg LLaanngguuaaggeess
English: Display the sum of A times B plus C.
C++: cout << (A * B + C);
Assembly Language:
mov eax,A
mul B
add eax,C
call WriteInt
Intel Machine Language:
A1 00000000
F7 25 00000004
03 05 00000008
E8 00500000

SSppeecciiffiicc MMaacchhiinnee LLeevveellss
(descriptions of individual levels
follow . . . )

HHiigghh--LLeevveell LLaanngguuaaggee
• Level 5
• Application-oriented languages
• C++, Java, Pascal, Visual Basic . . .
• Programs compile into assembly language
(Level 4)

AAsssseemmbbllyy LLaanngguuaaggee
• Level 4
• Instruction mnemonics that have a one-to-one
correspondence to machine language
• Calls functions written at the operating
system level (Level 3)
• Programs are translated into machine
language (Level 2)

OOppeerraattiinngg SSyysstteemm
• Level 3
• Provides services to Level 4 programs
• Translated and run at the instruction set
architecture level (Level 2)

IInnssttrruuccttiioonn SSeett AArrcchhiitteeccttuurree
• Level 2
• Also known as conventional machine
language
• Executed by Level 1 (microarchitecture)
program

MMiiccrrooaarrcchhiitteeccttuurree
• Level 1
• Interprets conventional machine instructions
(Level 2)
• Executed by digital hardware (Level 0)

DDiiggiittaall LLooggiicc
• Level 0
• CPU, constructed from digital logic gates
• System bus
• Memory
• Implemented using bipolar transistors
next: Data Representation

DDaattaa RReepprreesseennttaattiioonn
• Binary Numbers
• Translating between binary and decimal
• Binary Addition
• Integer Storage Sizes
• Hexadecimal Integers
• Translating between decimal and hexadecimal
• Hexadecimal subtraction
• Signed Integers
• Binary subtraction
• Character Storage

BBiinnaarryy NNuummbbeerrss
• Digits are 1 and 0
• 1 = true
• 0 = false
• MSB – most significant bit
• LSB – least significant bit
• Bit numbering:
MSB LSB
1 0 1 1 0 0 1 0 1 0 0 1 1 1 0 0
15 0

BBiinnaarryy NNuummbbeerrss
• Each digit (bit) is either 1 or 0
• Each bit represents a power of 2:
Every binary
number is a
sum of powers
of 2

TTrraannssllaattiinngg BBiinnaarryy ttoo DDeecciimmaall
Weighted positional notation shows how to calculate the
decimal value of each binary bit:
dec = (Dn-1 ´ 2n-1) + (Dn-2 ´ 2n-2) + ... + (D1 ´ 21) + (D0 ´ 20)
D = binary digit
binary 00001001 = decimal 9:
(1 ´ 23) + (1 ´ 20) = 9

TTrraannssllaattiinngg UUnnssiiggnneedd DDeecciimmaall ttoo BBiinnaarryy
• Repeatedly divide the decimal integer by 2. Each
remainder is a binary digit in the translated value:
37 = 100101

BBiinnaarryy AAddddiittiioonn
• Starting with the LSB, add each pair of digits, include
the carry if present.

IInntteeggeerr SSttoorraaggee SSiizzeess
Standard sizes:
What is the largest unsigned integer that may be stored in 20 bits?

HHeexxaaddeecciimmaall IInntteeggeerrss
Binary values are represented in hexadecimal.

TTrraannssllaattiinngg BBiinnaarryy ttoo HHeexxaaddeecciimmaall
• Each hexadecimal digit corresponds to 4 binary bits.
• Example: Translate the binary integer
000101101010011110010100 to hexadecimal:
Binary 000101101010011110010100 (2) equals hex 16A794 (16)

CCoonnvveerrttiinngg HHeexxaaddeecciimmaall ttoo DDeecciimmaall
• Multiply each digit by its corresponding power of 16:
dec = (D3 ´ 163) + (D2 ´ 162) + (D1 ´ 161) + (D0 ´ 160)
• Hex 1234(16) equals (1 ´ 163) + (2 ´ 162) + (3 ´ 161) + (4 ´ 160), or
decimal 4,660 (10)
• Hex 3BA4 (16) equals (3 ´ 163) + (11 * 162) + (10 ´ 161) + (4 ´ 160),
or decimal 15,268 (10)

PPoowweerrss ooff 1166
Used when calculating hexadecimal values up to 8 digits
long:

CCoonnvveerrttiinngg DDeecciimmaall ttoo HHeexxaaddeecciimmaall
decimal 422 (10) = 1A6 (16) hexadecimal

HHeexxaaddeecciimmaall AAddddiittiioonn
• Divide the sum of two digits by the number base (16). The quotient
becomes the carry value, and the remainder is the sum digit.
1 1
36 28 28 6A
42 45 58 4B
78 6D 80 B5
21 / 16 = 1, rem 5
Important skill: Programmers frequently add and subtract the
addresses of variables and instructions.

HHeexxaaddeecciimmaall SSuubbttrraaccttiioonn
• When a borrow is required from the digit to the left, add 16
(decimal) to the current digit's value:
16 + 5 = 21
-1
C6 75
A2 47
24 2E
Practice: The address of var1 is 00400020. The address of the next
variable after var1 is 0040006A. How many bytes are used by var1?

SSiiggnneedd IInntteeggeerrss
The highest bit indicates the sign. 1 = negative,
0 = positive
If the highest digit of a hexadecimal integer is > 7, the value is
negative. Examples: 8A, C5, A2, 9D

FFoorrmmiinngg tthhee TTwwoo''ss CCoommpplleemmeenntt
• Negative numbers are stored in two's complement
notation
• Represents the additive Inverse
Note that 00000001 + 11111111 = 00000000

BBiinnaarryy SSuubbttrraaccttiioonn
• When subtracting A – B, convert B to its two's
complement
• Add A to (–B)
0 0 0 0 1 1 0 0 0 0 0 0 1 1 0 0
– 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 1
0 0 0 0 1 0 0 1
Practice: Subtract 0101 from 1001.

FFoorrmm tthhee ttwwoo''ss ccoommpplleemmeenntt ooff aa
hheexxaaddeecciimmaall iinntteeggeerr
• Reverse all bits and add 1
• Easy way: subtract the digits from 15 and add 1
6A3D(16) → 95C2(16)→ 95C3

CCoonnvveerrtt ssiiggnneedd bbiinnaarryy ttoo ddeecciimmaall
• If the highest bit is a 1,
the number is in two’s
complement
• Form two’s
complement
• Convert decimal
number and attach a
minus sign to the
beginning of the
decimal integer
Starting value 11110000(2)
Step 1: Reverse the bits 00001111
Step 2: Add 1 to the value
from step 1
00001111
+ 1
Step 3: Form the two’s
complement
00010000
Step 4: Covert to decimal
and attach sign
-16(10)
• If the highest bit is a 0, convert it to decimal integer

CCoonnvveerrtt ssiiggnneedd ddeecciimmaall ttoo bbiinnaarryy
• Convert the absolute value
into binary
• If the original decimal
number is negative, form
the two’s complement of
the binary number
Starting value -16(10)
Step 1: Convert the
absolute value into
binary
00010000(2)
Step 2: Reverse the bits 11101111(2)
Step 3: Form the two’s
complement
11110000(2)

CCoonnvveerrtt ssiiggnneedd ddeecciimmaall ttoo hheexxaaddeecciimmaall
• Convert the absolute
value into hexadecimal
• If the original decimal
number is negative,
form the two’s
complement of the
hexadecimal number
Starting value -43(10)
Step 1: Convert the
absolute value into
hexadecimal
2B(16)
Step 2: Form the
two’s complement
D5(16)

CCoonnvveerrtt ssiiggnneedd hheexxaaddeecciimmaall ttoo ddeecciimmaall
• If the hexadecimal integer
is negative, form it’s two’s
complement otherwise
retain the integer as is
• Convert it to decimal
number. If the original
value is negative, attach a
minus sign to the
beginning of the decimal
integer
Starting value D5(16)
Step 1: Form the
two’s complement
2B(16)
Step 4: Covert to
decimal and
attach sign
- 43(10)

RRaannggeess ooff SSiiggnneedd IInntteeggeerrss
The highest bit is reserved for the sign. This limits the range:
Practice: What is the largest positive value that may be stored in 20 bits?

CChhaarraacctteerr SSttoorraaggee
• Character sets
• Standard ASCII (0 – 127)
• Extended ASCII (0 – 255)
• ANSI (0 – 255)
• Unicode (0 – 65,535)
• Null-terminated String
• Array of characters followed by a null byte
• Using the ASCII table
• back inside cover of book

NNuummeerriicc DDaattaa RReepprreesseennttaattiioonn
• pure binary
• can be calculated directly
• ASCII binary
• string of digits: "01010101"
• ASCII decimal
• string of digits: "65"
• ASCII hexadecimal
• string of digits: "9C"
next: Boolean Operations

BBoooolleeaann OOppeerraattiioonnss
• NOT
• AND
• OR
• Operator Precedence
• Truth Tables

BBoooolleeaann AAllggeebbrraa
• Based on symbolic logic, designed by George Boole
• Boolean expressions created from:
• NOT, AND, OR

NNOOTT
• Inverts (reverses) a boolean value
• Truth table for Boolean NOT operator:
Digital gate diagram for NOT:
NOT

AANNDD
• Truth table for Boolean AND operator:
Digital gate diagram for AND:
AND

OORR
• Truth table for Boolean OR operator:
Digital gate diagram for OR:
OR

OOppeerraattoorr PPrreecceeddeennccee
• Examples showing the order of operations:

TTrruutthh TTaabblleess ((11 ooff 33))
• A Boolean function has one or more Boolean inputs,
and returns a single Boolean output.
• A truth table shows all the inputs and outputs of a
Boolean function
Example: ØX Ú Y

• Example: X Ù ØY

• Example: (Y Ù S) Ú (X Ù ØS)
Two-input multiplexer

SSuummmmaarryy
• Assembly language helps you learn how software is
constructed at the lowest levels
• Assembly language has a one-to-one relationship
with machine language
• Each layer in a computer's architecture is an
abstraction of a machine
• layers can be hardware or software
• Boolean expressions are essential to the design of
computer hardware and software

5544 6688 6655 2200 4455 66EE 6644
What do these numbers represent?

Chapt 01

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