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Important Concepts
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Parts of the CPU
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Arithmetic/Logic Unit
Control Unit
Registers
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Program Counter
Instruction Register
Fetch/Decode/Execute Cycle
Machine Language
Stored-Program Concept
Bus
Direct Memory Access
Types of Instructions
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Transfer Operations
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Arithmetic/Logic Operations
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Load
Store
Addition, Subtraction, Multiplication, ...
AND, OR, NOT, XOR
Shift, Rotate
Control Operations
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Unconditional Jump
Conditional Jump (Jump if Register > 0)
Halt
Additional Types of Instructions
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Input/Output Instructions
Direct Memory Access Instructions
Graphics Operations
Reduced Instruction Set Computer
Minimal set of instructions
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Complex operations are divided into simple steps
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Simple steps are encoded as the instructions
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Macro-instructions are small programs, called
microcode
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Instructions execute very quickly
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Faster cycle, but requires more operations
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Chips require less power consumption
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Complex Instruction Set Computer
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Complex instructions
Require more time to execute, but do more
More, specialized, operations
Can include memory, graphic operations
Instructions slower to execute, but do more
Stored Program Concept
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Program can be treated as data
Program can be changed in memory, read/written
to storage
Allows computer to be flexible
Different kinds of programs:
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Machine code
Assembly Language
High-level Language
Logic Programming
Programs can be translated from one from to
another
Machine Instructions
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Instructions are encoded as binary strings, e.g.,
1011000111000
Instructions have op-codes and operands
Operands are the data (or where to find the data)
Op-code specifies the operation that is done to the
data
Instructions may be fixed or variable length
Fetch/Decode/Execute Cycle
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The program counter keeps track of the next
instruction to be executed
The next instruction is fetched and place into the
instruction register
The control unit decodes the instructions –
interprets the op-code, finds the operands
The instruction is executed – the control unit
causes the ALU to do the proper operation based
on the op-code
A Jump instruction may change the program
counter