Computer Hardware

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Computer Hardware

• What goes on inside?

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(No Transcript)
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Deeper
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Deeper
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Not that deep
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A simple Computer
Performs all calculations and decisions Add,
Subtract, gt, lt, decide what to do next
Central Processing Unit CPU
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A simple Computer
Memory
Central Processing Unit CPU
Stores most information Memory is a large array
of integers
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Memory - array of integers

• How does it store text?
• How does it store images?
• How does it store audio?
• How does it store a program?

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A simple Computer
Memory
Central Processing Unit CPU
Address
Wires that pass the index of the location in
memory that the CPU wants to get or change
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A simple Computer
Address
Memory
Central Processing Unit CPU
0
1
0
0
1
0
Wires that pass the index of the location in
memory that the CPU wants to get or change
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A simple Computer
Address
Memory
Central Processing Unit CPU
0
1
0
0
1
0
Number of wires number of bits Number of bits
range of possible indexes total
possible memory
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A simple Computer
Address
Memory
Central Processing Unit CPU
0
1
0
0
1
0
Twice as much memory adds how many more address
wires? 1 more
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A simple Computer
Memory
Central Processing Unit CPU
Address
Data
Wires that pass numbers from CPU to Memory or
from Memory to CPU
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A simple Computer
Memory RAM
Central Processing Unit CPU
Address
Data
RAM - Random Access Memory is the main memory of
a computer. The size of RAM is the length of the
array
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How to represent a program in memory

• Program is a series of simple instructions
• Each instruction is an integer
• CPU
• Goes to a location in memory
• Gets an instruction
• Does what the instruction says
• Moves to the next instruction
• Does this millions of times per second

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A simple fake computer
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Program Counter - address (index) of the next
instruction
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Registersprivate memory for the CPU
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Every instruction has a number

• OpCodes
• 0 - Halt
• 1 - Load
• 2 - Store
• 3 - Add
• 4 - Subtract
• 5 - Divide
• 6 - Multiply
• 7 - Is Greater Than 0?
• 8 - Goto
• 9 - Branch If Greater Than 0!

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OpCodes 0 - Halt 1 - Load 2 - Store 3 -
Add 4 - Subtract 5 - Divide 6 - Multiply 7 -
Is Greater Than 0? 8 - Goto 9 - Branch If
Greater Than 0!

• Instruction Format
• Digit 1 OpCode
• Digit 2 Register
• Digit 3-4 Memory Address

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OpCodes 0 - Halt 1 - Load 2 - Store 3 -
Add 4 - Subtract 5 - Divide 6 - Multiply 7 -
Is Greater Than 0? 8 - Goto 9 - Branch If
Greater Than 0!

• Instruction Format
• Digit 1 OpCode
• Digit 2 Register
• Digit 3-4 Memory Address

3 1 10
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OpCodes 0 - Halt 1 - Load 2 - Store 3 -
Add 4 - Subtract 5 - Divide 6 - Multiply 7 -
Is Greater Than 0? 8 - Goto 9 - Branch If
Greater Than 0!

• Instruction Format
• Digit 1 OpCode
• Digit 2 Register
• Digit 3-4 Memory Address

3 1 10
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Reg1Reg1Mem10
OpCodes 0 - Halt 1 - Load 2 - Store 3 -
Add 4 - Subtract 5 - Divide 6 - Multiply 7 -
Is Greater Than 0? 8 - Goto 9 - Branch If
Greater Than 0!

• Instruction Format
• Digit 1 OpCode
• Digit 2 Register
• Digit 3-4 Memory Address

3 1 10
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?
OpCodes 0 - Halt 1 - Load 2 - Store 3 -
Add 4 - Subtract 5 - Divide 6 - Multiply 7 -
Is Greater Than 0? 8 - Goto 9 - Branch If
Greater Than 0!

• Instruction Format
• Digit 1 OpCode
• Digit 2 Register
• Digit 3-4 Memory Address

4 2 30
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Reg2Reg2-Mem30
OpCodes 0 - Halt 1 - Load 2 - Store 3 -
Add 4 - Subtract 5 - Divide 6 - Multiply 7 -
Is Greater Than 0? 8 - Goto 9 - Branch If
Greater Than 0!

• Instruction Format
• Digit 1 OpCode
• Digit 2 Register
• Digit 3-4 Memory Address

4 2 30
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A simple program
1 0 07
Load location 7 into register 0
Reg0Mem7 PC PC1
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A simple program
1 2 08
Load location 8 into register 2
Reg2Mem8 PC PC1
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A simple program
3 0 07
Add location 7 to register 0
Reg0Reg0Mem7 PC PC1
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A simple program
8 2 00
GOTO the address stored in register 2
PC Reg2
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A simple program
3 0 07
Add location 7 to register 0
Reg0Reg0Mem7 PCPC1
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A simple program
8 2 00
GOTO the address stored in register 2
PC Reg2
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A simple program
3 0 07
Add location 7 to register 0
Reg0Reg0Mem7 PCPC1
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Clock speed of a processor

• Number of instructions per second that can be
  performed
• 100 MHz 100 Million times per second
• 1.5 GHz 1.5 Billion instructions per second

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So what is a program?

• A file of bytes
• Operating system copies the file into memory
• When select the program from Start menu
• When you double click on the program
• Operating system sets PC to address of first byte
  of the program in memory
• Program begins to run

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Programs and Data
Program (instructions)

• Data

What is the difference?
If the PC points to it then it is an instruction
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Review

• CPU - Central Processing Unit
• Does calculating and deciding
• Memory - RAM
• Stores data and programs
• Array of integers
• Size of RAM the length of this array

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Review

• Program
• List of instructions
• Each instruction is an integer that the CPU
  decodes
• Program counter (PC) is the address of the next
  instruction
• Copy program from file into memory
• Set PC to start of the program