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Computers: How They Work. What is a Computer Components of Computer World’s First Computers and CPUs Mother Board Machine Code and the processor’s Instruction Set – Software Memory types (ROM, DRAM, SRAM, FLASH) Hard Drive Compact Disk Keyboard Monitor The Mouse Other I/O

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computers how they work

Computers: How They Work

What is a Computer

Components of Computer

World’s First Computers and CPUs

Mother Board

Machine Code and the processor’s Instruction Set – Software

Memory types (ROM, DRAM, SRAM, FLASH)

Hard Drive

Compact Disk



The Mouse

Other I/O

DSL and connection to Internet

File Compression


PC Mother Boards


Hard Drive

Magnetic Tape

Punch Cards


SIMM cards

Polarized Films



CCD chips

what is a computer
What is a Computer?

A machine that stores instructions and data and operates on information/data.


Jacquards Loom

Circa 1804

charles babbage s first attempt at a computer the analytical engine c 1822
Charles Babbage’s first attempt at a Computer The Analytical Engine, c. 1822

Designed to use Jacquard punch cards to store and run a program


Augusta Ada Lovelace, created programs

Steam Powered

25,000 parts

15 tons and 8 feet high

Never completed

difference engine ii
Difference Engine II
  • Designed to calculate polynomials and compute trig and log functions
  • C. 1847
  • Crank operated

  • A logic machine that can execute a a small set of instructions.
  • A Central Processing Unit (CPU) integrated into a single chip

(i.e. constructed as an integrated circuit on a single piece of Silicon)

components of a computer
Components of a Computer







Registers, Cache)


(Monitor, speakers,

USB Drive, Printer,

DSL, Hard Drive)


(Keyboard, Mouse

USB Drive, DSL,

Touchscreen, Microphone,

Hard Drive)

USB – Universal Serial Bus DSL – Digital Subscriber Line

what s inside a basic cpu central processing unit
What’s Inside a basic CPU?(Central Processing Unit)

ALU (Arithmetic Logic Unit)

Performs addition, division, etc.

Instruction Decoder

Program Counter

Instruction Register – stores current instruction being worked on.

Data Registers – stores current data being worked with.

Accumulator (place for storing a sum)

Clock for sequencing operations

memory a device that remembers a previous input
Memory – A Device that “remembers” a previous input.

Registers are the high speed memory on the CPU chip. These registers are used for storing data that is frequently needed.

Instructions are pre-fetched and stored in registers too so that they are ready when needed.

1 bit latch flip flop
1-bit Latch (Flip Flop)

Static RAM and registers are constructed with this logic. The state of Q is retained as long as power is on.

Static RAM –Non-volatile Random Access Memory


Memory Hierarchy

cache memory
Cache Memory


Static Random Access Memory

Retains data in memory as long as power is on

Uses flip flops (8 transistors each)

Fast but more expensive due to more chip real-estate needed for each memory location compared to DRAM

Used for cache memory

Fast Access time  10 nanoseconds

dram and sdram

Dynamic RAM

Dynamic refers to the need to refresh the data

Synchronous DRAM

(Timing of memory chip is synchronized with CPU clock)

Data is stored as electrical charge in capacitors

Capacitors will discharge requiring that memory be refreshed every few milliseconds.

Dense therefore least expensive form of memory


The word “random” means bytes can be accessed randomly. Data access is not sequential like a magnetic tape.

simm dimm

Single In-line memory module

Dual In-line memory module

These cards are DRAMS

rom of three memory locations each word of memory is 3 bits
ROM of three memory locations, each “word” of memory is 3 bits

Read Only Memory

Data contents can not be changed

Data retained even when power is off

Manufactured with the data

Used for booting up computer and loading Operating System

Device Driver software


flash memory
Flash Memory
  • (Electrically Eraseable Programmable Memory)
  • Using Floating Gate Transistors to store bits
  • Non-volatile (power not needed to maintain data)
  • MP3 Players are flash drives with extra circuitry to decode data to analog music signals
  • Cellular Phones
  • Digital Cameras
  • Very resistant to temperature, shock, field stress

hard drive 120 240 gbytes
Hard Drive120-240 GBytes

Data stored magnetically

Permanent Storage, Non-volatile memory

Fast - Spins 4,500 to 12,000 rpm

Dense and Inexpensive

Data easily erased and rewritten

Iron Oxide or very thin magnetic film applied with a sputtering process stores magnetic data

Not random access




Actuator Arm


Read/Write head

read write head
Read-Write Head

Multiple Platters

Head 20-50 nm from platter surface

A human hair is 100 nm

How Stuff Works


the voice coil actuator controls the movement of the actuator arm
The voice-coil actuator controls the movement of the actuator arm
  • Positions the read/write heads
  • Similar to a speaker!
  • Uses a coil and permanent magnet
  • Converts electrical signals into mechanical movement
  • In this picture, magnet has been moved to the left during disassembly to expose the coil
  • Coil moves freely under the magnet

small tolerances
Small Tolerances

5-80 Mbytes/sec media transfer rate

software commands hardware
Software commands Hardware

while (amt2 <= amt1)


amt1 = amt1 + 100;

amt2 = amt2 + 0.05*amt2;



14: while (amt2 <= amt1)

004015BB fld dword ptr [ebp-8]

004015BE fcomp dword ptr [ebp-4]

004015C1 fnstsw ax

004015C3 test ah,41h

004015C6 je main+70h (004015f0)

15: {

16: amt1 = amt1 + 100;

004015C8 fld dword ptr [ebp-4]

004015CB fadd dword ptr [__real@4@4005c800000000000000 (0046f0a4)]

004015D1 fstp dword ptr [ebp-4]

17: amt2 = amt2 + 0.05*amt2;

004015D4 fld dword ptr [ebp-8]

004015D7 fld dword ptr [ebp-8]

004015DA fmul qword ptr [__real@8@3ffaccccccccccccd000 (0046f098)]

004015E0 faddp st(1),st

004015E2 fstp dword ptr [ebp-8]

18: year++;

004015E5 mov eax,dword ptr [ebp-14h]

004015E8 add eax,1

004015EB mov dword ptr [ebp-14h],eax

19: }

C++ high level codes gets compiled/translated into low level machine codes

fetch decode execute cycle
Fetch-Decode-Execute Cycle
  • Fetch an Instruction:
    • Fetch instruction at address stored in address register
    • Increment Program Counter
    • Load the Instruction Register with this Instruction
    • Decode the Instruction
    • Fetch the operands
  • Execute
    • ALU or other logic performs the operation
    • The result is then written to memory or to a register.
a computer is much more than a processor
A Computer is much more than a processor….

Processor Intel® Core™2 Q6600 Quad-Core (8MB L2 cache,2.4GHz,1066FSB)

Video Cards 768MB nVidia GeForce 8800 GTX

Memory 2GB* Dual Channel DDR2 SDRAM at 667MHz - 2 DIMMs

Hard Drive: 500GB* - 7200RPM, SATA 3.0Gb/s, 16MB Cache

Optical Drive Single Drive: Blu-ray Disc Drive (BD/DVD/CD burner w/double layer BD write

Monitors 20 inch E207WFP Widescreen Digital Flat Panel



micron = 10-6 meters

The feature size of an integrated circuit is indicated by the width of a "wire," measured in microns (one micron is one millionth of a meter). Analysis and Design of Analog Integrated Circuits (4th Edition)