assembly language -- overview cisp 310 prof. chapman
TRANSCRIPT
Assembly Language -- Overview
CISP 310Prof. Chapman
CRC CISP 310 Chapman
Assembly Language Is…
Not A High-Level Language
CRC CISP 310 Chapman
High-Level Languages (HLL)
void main() { do something }
*.c file
Compiler not text,binary
*.obj file
not text,binary
*.exe file
Linker
C libraryfiles (existing *.obj files)
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High-Level Languages (HLL)
C language program
*.c file
Programmer’s focus is on getting the syntax and structured logic correct inthe source code
CRC CISP 310 Chapman
High-Level Languages
C++ languageprogram
Object-oriented (OO)
*.cpp file
Programmer’s focus is on getting the syntax and OO logic correct
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HLL Development Techniques
Compiler catches syntax mistakes
Compiler translates from text into processor-specific binary codes (object file)
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HLL Development Techniques
Memory for data storage and program code itself is automatically allocated
Linker creates *.exe file
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Assembly is Not a HLL
An assembly programmer has to deal directly with the processor memory (RAM)
The instructions are much more cryptic like “move data to a different memory address”
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Assembly is Not a HLL
We must write code to enable I/O between keyboard, files, and monitor (generally using operating system procedures)
We must use a different design philosophy besides OO
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Assembly is Not a HLL
Loop and if logic is implemented differently in assembly than with HLL
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HLL OO Procedure
Let’s look at the code that defines the effect of clicking thisButton control (VB.NET language)
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' called when Call Peedy button is clicked Private Sub btnCall_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles btnCall.Click m_objMSpeaker.Show(0)
' move Peedy to a specified location m_objMSpeaker.MoveTo(Convert.ToInt16(Cursor.Position.X - 100), Convert.ToInt16(Cursor.Position.Y + 130))
m_objMSpeaker.Play("Wave")
' tell Peedy what to say m_objMSpeaker.Speak("Hello, I'm Peedy. Please say or select the name of the person whose phone number you would like to find.", "")
m_objMSpeaker.Speak("If you wish to say the name, press the Scroll Lock key then speak the name.", "")
m_objMSpeaker.Play("RestPose")
cboName.Enabled = True btnCall.Enabled = False End Sub ' btnCall_Click
HLL comment
subroutine with 7 HLL statements
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HLL Translated Into Assembly
Every high-level instruction is equivalent to a group of many assembly instructions
Each assembly instruction is cryptic
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m_objMSpeaker.Speak("Hello, I'm Peedy. Please say or select the name of the person whose phone number you would like to find.", "")
This HLL statement
Eight Assembly statements000000f5 mov esi,dword ptr [ebx+000000ECh] 000000fb push dword ptr ds:[02050024h] 00000101 mov ecx,esi 00000103 mov edx,dword ptr ds:[020529C4h] 00000109 mov eax,dword ptr [ecx] 0000010b mov eax,dword ptr [eax+0Ch] 0000010e mov eax,dword ptr [eax+000001ACh] 00000114 call dword ptr [eax+5Ch]
=
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Sample AssemblyAssembly Instruction
000000f5 mov esi,dword ptr [ebx+000000ECh]
operation code operands
register (memory)
hexadecimalconstant
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Assembly Language Is…
Not Self-Documenting
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What Does This Accomplish?
000000f5 mov esi,dword ptr [ebx+000000ECh]
000000fb push dword ptr ds:[02050024h]
00000101 mov ecx,esi
00000103 mov edx,dword ptr ds:[020529C4h]
00000109 mov eax,dword ptr [ecx]
0000010b mov eax,dword ptr [eax+0Ch]
0000010e mov eax,dword ptr [eax+000001ACh]
00000114 call dword ptr [eax+5Ch]
00000117 nop Huh?
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What’s Difficult About Assembly?
Cannot easily see purpose of code segment (see previous slide)
Not portable (separate assembly instructions for Intel, Motorola, … processors)
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What’s Right With Assembly?
Every language is based on machine code, and assembly is closest to machine code
Assembly is necessary to write high-level language translators Java/C++/C#/VB.NET/Fortran/…)
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What’s Right With Assembly?
We can write I/O code to communicate between our program and peripherals (cameras, iPods, etc.)
We can write instructions that are optimized for our processor, creating very very small and very very fast programs
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What You Will Learn
At the end of this course, you will be able to create simple command-line programs that accept input from the keyboard and display text output to the monitorYou will finally understand the structure of memory and the inner workings of the processor chip
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Ending Metaphor
HLL programmers: authors who develop the content of a book but leave the details of typesetting, printing, sales, and distribution to someone else
Assembly programmers: authors who can both write and publish, sell, and distribute their own books. They understand programming at a deeper level than a HLL programmer.