A Hierarchy of Languages
 Application Programs
 High-Level Languages
 Machine independent
 Machine specific
 Assembly Language
 Machine Language
 Hardware
 Computer Organization and Architecture 
High-Level Language
 Low-Level Language
 Dr.Tarek Abdul Hameed
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Assembly and Machine Language
 ?Used to wire and interconnect the various components
 23 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
Fetch - Execute Cycle
 Infinite Cycle implemented in Hardware
 Instruction Fetch
 Instruction Decode
 Execute
 Memory Access
 Writeback Result
 Computer Organization and Architecture 
Fetch instruction
 Compute address of next instruction
 Generate control signals for instruction
 Read operands from registers
 Compute result value
 Read or write memory (load/store)
 Writeback result in a register
 Dr.Tarek Abdul Hameed
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Microprocessors Building Blocks
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
 25
Microprocessor
 Memory
 Bus
 RAM
 I/O
 Data
 Cache
 Control
 Unit
 Bus
 Interface
 Unit
 System
 Bus
 Instruction
 Decoder
 Instruction
 Cache
 Computer Organization and Architecture 
Arithmetic
 & Logic
 Unit
 Registers
 Floating
 Point
 Unit
 Registers
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 Dr.Tarek Abdul Hameed
Bus Interface Unit
 ?Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Translating Languages
 Program (C Language):
 swap(int v[], int k) {
 int temp;
 temp = v[k];
 v[k] = v[k+1];
 v[k+1] = temp;
 }
 Compiler
 MIPS Assembly Language:
 sll $2,$5, 2
 add $2,$4,$2
 lw  $15,0($2)
 lw  $16,4($2)
 sw  $16,0($2)
 sw  $15,4($2)
 jr  $31
 Computer Organization and Architecture 
A statement in a high-level 
language is translated 
typically into several 
machine-level instructions
 MIPS Machine Language:
 Assembler
 00051080
 00821020
 8C620000
 8CF20004
 ACF20000
 AC620004
 03E00008
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 Dr.Tarek Abdul Hameed
Advantages of High-Level Languages
 ?Also known as the "Integer Unit"
 ? It performs whole-number math calculations (subtract, multiply, divide, etc)
 comparisons (is greater than, is smaller than, etc.) and logical operations (NOT,
 OR, AND, etc)
 ? The new breed of popular microprocessors have not one but two almost identical
 ALU's that can do calculations simultaneously, doubling the capability
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Floating-Point Unit (FPU)
 ? Also known as the "Numeric Unit"
 ?Sparc, Ultra Sparc 1985 0n
 ?Allows you to view machine instructions, memory, and registers
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
 12
Assemble and Link Process
 Source
 File
 Source
 File
 Assembler
 Assembler
 Source
 File
 Assembler
 Object
 File
 Object
 File
 Object
 File
 Linker
 Link
 Libraries
 Executable
 File
 A project may consist of multiple source files
 Assembler translates each source file separately into an object file
 Linker links all object files together with link libraries
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
 13
Components of a Computer System
 Computer
 ?Network: newly added component for communication
 Memory
 Control
 Processor
 Datapath
 I/O Devices
 Input
 B
 U
 S
 Network
 Computer Organization and Architecture 
Output
 Disk
 Dr.Tarek Abdul Hameed
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Memory
 ?Tasks include fetching instructions & data, storing data, managing input/output
 devices
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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That was the structure, now let's 
talk about the language of a 
microprocessor 
Computer Organization and Architecture 
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 Dr.Tarek Abdul Hameed
Instruction Set
 ?Most new PC's are equipped with this RAM which is able to synchronize itself
 with the processor, enabling data transfer at more than twice the speed of
 previous RAM technologies)
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 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
Main (Internal) Memory
 ?Control: generates control signals for each instruction
 Next Program
 Counter
 Program Counter
 Instruction
 Cache
 Instruction
 Registers
 A
 L
 U
 Data
 Cache
 Control
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Datapath Components
 ?Then, it passes on the decoded instruction to the ALU or FPU
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Arithmetic & Logic Unit (ALU)
 ?Bigger instruction-sets mean more complex chips (higher costs, reduced
 efficiency), but shorter programs
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Instruction Set Architecture (ISA)
 ?DRAM is called Dynamic RAM because the memory content needs to be
 refreshed periodically (every few milliseconds) due to leakage of electrical
 charge.Indirectly via an assembler
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Compiler and Assembler
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Instructions and Machine Language
 ?SRAMis called static because the memory retains its contents as long as power is
 supplied-It does not have to be periodically refreshed as in DRAM. It is used to store BIOS (Basic Input/Output System-helps to load and locate an operating
 system), external to microprocessor, and computer instruction sets, internal to
 microprocessor
 ?Writing to a PROM destroys the internal links, so a basic PROM can only be
 programmed once
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 Dr.Tarek Abdul Hameed
 Computer Organization and Architecture 
The Need for a Memory Hierarchy
 ?Access time: milliseconds
 Faster
 Memory Bus
 Memory
 I/O Bus
 Bigger
 Disk, Tape, etc
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Processor
 ?Also receives the processed data and sends it to the main memory
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Instruction Decoder
 ?However, Assembly language programs are not portable
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Why Learn Assembly Language?Writing compact code
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Assembly Language Programming Tools
 ?Up to 264 bytes of physical address space
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 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
Address Space
 Computer Organization and Architecture 
Address Space is the 
set of memory 
locations (bytes) that 
can be addressed
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 Dr.Tarek Abdul Hameed
Address, Data, and Control Bus
 ?When you turn the computer on, ROM automatically prepares the computer system
 and loads the initial display screen prompt
 ?This unit receives the programming instructions and decodes them into a form that 
is understandable by the processing units, i.e. the ALU or FPU
 ?TheALUcandothese calculations as well, but will do them very slowly
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Registers
 ?Processed data goes back to the data cache and then to main memory from these
 registers
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Control Unit
 ?Alpha (now Compaq, now HP) in 1990's
 Computer Organization and Architecture 
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 Dr.Tarek Abdul Hameed
More computer families
 ?Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Instruction Fields
 ?Operands fields which specify where to get the source and destination operands
 for the operation specified by the opcode.Cache memory is small in size but fast
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Typical Memory Hierarchy
 ?input-output control
 Computer Organization and Architecture 
Dr.Tarek Abdul Hameed
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Some Computer families
 ?Avariation of ROM is PROM (Programmable Read Only Memory), in which the user
 can load programs and data that are read only.It performs calculations that involve numbers represented in the scientific
 notation (also known as floating-point numbers).Compatibility of software between various implementations
 ?RAM-RandomAccessMemory.??????..??????????