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COS2621 SUMMARY
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COS2621Summary
,Chapter 1 - Introduction
Chapter 1 - Introduction
Summary
1.1 Organization and Architecture
Computer architecture - refers to those attributes of a system visible to a programmer, ie: those attributes
that have a direct impact on the logical execution of a program.
Examples are: instruction set, number of bits used to represent various data types, I/O mechanisms, and
techniques for addressing memory.
Computer organization - refers to the operational units and their interconnections that realize the
architectural specifications.
Examples are: hardware details transparent to the programmer such as - control signals, interfaces between
the computer and peripherals, and the memory technology used.
The distinction between architecture and organization is important. Manufacturers offer a family of computer
models with the same architecture, but with differences in organization. Different models in the family have
different price and performance characteristics. A particular architecture may span many years, with its
organization changing with changing technology.
1.2 Structure and Function
Structure - The way in which the components are interelated.
Function - The operation of each individual component as part of the structure.
Function
There are four basic functions that a computer can perform -
• Data processing - Computer must be able to process data;
• Data storage - Must be able to store data that is being processed, as well as long-term storage;
• Data movement - Must be able to move data between itself and the outside world. When data are
received or delivered to a device that is directly connected to the computer, the process is known as
input-output (I/O), and the device is referred to as a peripheral. When data are moved over longer
distances, to or from remote devices, the process is known as data communications.
• Control - Must be control of above 3 functions. Ultimately control is exercised by the programmer,
who provides computer with instructions. Within the computer a control unit manages the computers'
resources, in response to those instructions.
Structure
Four main structural components - (There may be one or more of each)
• Central Processing Unit (CPU) - Controls the operation of the computer and performs its data
processing functions;
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, Chapter 1 - Introduction
◦ Control unit - Controls the operation of the CPU and hence the computer;
◦ Arithmetic and logic unit (ALU) - Performs the computers' data processing functions;
◦ Registers - Provides storage internal to the CPU;
◦ CPU interconnection - Mechanism that provides for communication among the control unit,
ALU, and registers.
• Main memory - Stores data;
• I/O - Moves data between the computer and its external environment;
• System interconnection - provides for communication among CPU, main memory, and I/O -
system bus.
0.3 Why study Computer Organization & Architecture ? (Read Appendix B: Assembly Language - Text
book)
Computer organization and architecture encompasses a broad range of design issues and concepts. A good
overall understanding of these concepts will be useful in other areas of study and work.
Why study Assembly language -
• Assembly language code is often much smaller and faster than code written in a high-level
language;
• We could speed up the execution time of a program if those parts of the program that are performed
frequently are written in assembly language;
• With assembly language programming we have complete access to hardware. This is not possible
with high-level languages;
• A basic understanding of low-level programming is essential for understanding the intricacies of
compilers and operating systems;
• It is easier to understand the operation of a computer at the architctural level if we have knowledge
of assembly language.
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, Chapter 1 - Introduction
Key Terms
• arithmetic and logic unit (ALU) - A part of a computer that performs arithmetic operations, logic
operations, and related operations.
• central processing unit (CPU) - Controls the operaton of a computer, and performs its data
processing functions.
• computer architecture - refers to those attributes of a system visible to a programmer, ie: those
attributes that have a direct impact on the logical execution of a program.
• computer organization - refers to the operational units and their interconnections that realize the
architectural specifications.
• control unit - Controls the operation of the CPU, and hence the computer.
• input-output (I/O) - Refers to the movement of data between a computer and a directly attached
peripheral, or other remote devices.
• main memory - Program addressable storage from which instructions and other data can be
loaded directly into registers for subsequent execution or processing
• processor - See Central Processing Unit (CPU).
• registers - Provide storage internal to the CPU.
• system bus - Interconnection between CPU, main memory, and I/O; consisting of a number of
conducting wires attached to all the other components.
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