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Computer Hardware
What goes on inside?
Deeper
Deeper
Not that deep
A simple Computer
CentralProcessing
Unit
CPU
Performs all calculations and decisions
Add, Subtract, …>, <, ==decide what to donext
A simple Computer
CentralProcessing
Unit
CPU
Memory
Stores most information
Memory is a large array of integers
0 1231 2342 123 3414 -235 31246 127 42318 29 -2310 011 70212 3613 102314 -6915 937216 3617 1269318 619 -69
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?
0 1231 2342 123 3414 -235 31246 127 42318 29 -2310 011 70212 3613 102314 -6915 937216 3617 1269318 619 -69
A simple Computer
CentralProcessing
Unit
CPU
Memory
Address
Wires that pass the index of the location in memory thatthe CPU wants to get or change
A simple Computer
CentralProcessing
Unit
CPU
Memory
Address
Wires that pass the index of the location in memory thatthe CPU wants to get or change
010010
A simple Computer
CentralProcessing
Unit
CPU
Memory
Address
Number of wires = number of bitsNumber of bits = range of possible indexes
= total possible memory
010010
A simple Computer
CentralProcessing
Unit
CPU
Memory
Address
Twice as much memory adds how many more address wires?
1 more
010010
A simple Computer
CentralProcessing
Unit
CPU
Memory
Address
Data
Wires that pass numbers from CPU to Memoryor from Memory to CPU
A simple Computer
CentralProcessing
Unit
CPU
Memory
RAM
Address
Data
RAM - Random Access Memory is the main memory of a computer.
The size of RAM is the length of the array
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
A simple fake computer
CPU
Program Counter - address (index) of the next
instruction
Registersprivate memory for the CPU
Every instruction has a number
OpCodes 0 - Halt1 - Load2 - Store3 - Add4 - Subtract5 - Divide6 - Multiply7 - Is Greater Than 0?8 - Goto9 - Branch If Greater Than 0!
Instruction Format:
Digit 1 OpCode
Digit 2 Register
Digit 3-4 Memory Address
OpCodes 0 - Halt1 - Load2 - Store3 - Add4 - Subtract5 - Divide6 - Multiply7 - Is Greater Than 0?8 - Goto9 - Branch If Greater Than 0!
Instruction Format:
Digit 1 OpCode
Digit 2 Register
Digit 3-4 Memory Address
OpCodes 0 - Halt1 - Load2 - Store
3 - Add4 - Subtract5 - Divide6 - Multiply7 - Is Greater Than 0?8 - Goto9 - Branch If Greater Than 0!
3 1 10
Instruction Format:
Digit 1 OpCode
Digit 2 Register
Digit 3-4 Memory Address
OpCodes 0 - Halt1 - Load2 - Store
3 - Add4 - Subtract5 - Divide6 - Multiply7 - Is Greater Than 0?8 - Goto9 - Branch If Greater Than 0!
3 1 100 751 -3302 423 13
Reg[1]=Reg[1]+Mem[10]
Instruction Format:
Digit 1 OpCode
Digit 2 Register
Digit 3-4 Memory Address
OpCodes 0 - Halt1 - Load2 - Store
3 - Add4 - Subtract5 - Divide6 - Multiply7 - Is Greater Than 0?8 - Goto9 - Branch If Greater Than 0!
3 1 100 751 -3302 423 13
?
Instruction Format:
Digit 1 OpCode
Digit 2 Register
Digit 3-4 Memory Address
OpCodes 0 - Halt1 - Load2 - Store3 - Add4 - Subtract5 - Divide6 - Multiply7 - Is Greater Than 0?8 - Goto9 - Branch If Greater Than 0!
4 2 30
Reg[2]=Reg[2]-Mem[30]
Instruction Format:
Digit 1 OpCode
Digit 2 Register
Digit 3-4 Memory Address
OpCodes 0 - Halt1 - Load2 - Store3 - Add
4 - Subtract5 - Divide6 - Multiply7 - Is Greater Than 0?8 - Goto9 - Branch If Greater Than 0!
4 2 30
A simple program
1 0 07
Load location 7 into register 0
Reg[0]=Mem[7]PC = PC+1
A simple program
1 2 08
Load location 8 into register 2
Reg[2]=Mem[8]PC = PC+1
A simple program
3 0 07
Add location 7 to register 0
Reg[0]=Reg[0]+Mem[7]PC = PC+1
A simple program
8 2 00
GOTO the address stored in register 2
PC = Reg[2]
A simple program
3 0 07
Add location 7 to register 0
Reg[0]=Reg[0]+Mem[7]PC=PC+1
A simple program
8 2 00
GOTO the address stored in register 2
PC = Reg[2]
A simple program
3 0 07
Add location 7 to register 0
Reg[0]=Reg[0]+Mem[7]PC=PC+1
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
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
Programs and Data
Program (instructions)
Data
What is the difference?
If the PC points to itthen it is an instruction
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
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
