Computer Basics
      A computer is a machine that … 
      How long have electronic computers been around?
      Why were they invented?
      Why are they so important now?
      Are they smart?
      What is THE characteristic of that makes computers so good at what they do?
      How do we get them to do what we want?
      Computers are comprised of both  _____ (tangible) & _____ (intangible)
   Hardware needs software and software needs hardware
   

   5 Main Hardware Components
     

       CPU - what does it do? how fast does it do it? who makes these? 
            what is an example of one?  IR/IP/Reg/CU/ALU? 
            what are the steps of instruction execution?
       RAM - what does it do?  how is it organized?  what IS a byte?   
             how much RAM is there?  how is cache related to RAM?  
             how are things represented in RAM?
       SS - what does it do?  why is it needed?  what kinds of SS are there? 
            how big is SS?   how is SS different from RAM?
       INPUT - what does I/O do?  how does it work? 
               how do you get pictures/music  into a computer?
       OUTPUT - what does I/O do?  how does it work? 
               how do you get pictures/music out of a computer?
               
       How do signals travel between components? 
       
   
 What is the ONLY language that computers understand?

emu: hardware overview

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 How is Software Executed?
 =========================
1. User enters a command to the ______ to run the program
2. OS (loader) retrieves program from ______ and store into _______
3. Address of first instruction to be executed is put into the _______ .
4. Instruction is fetched from RAM and placed into the  ________.
   Update the IP
6. Instruction in IR is decoded
   Fetch operands as needed
7. Instruction is executed
   Store result as needed
   Set status flags
8. Go to 4 if not done
9. When done, control is given back to the _____


fetch - decode - execute cycle
happens HOW fast???

How do we measure time?

CLOCK
Hertz? = 1 clock tick per second
 Megahertz = 1 million ticks per sec (each tick = 1 microsecond)
 Gigahertz = 1 billion ticks per sec (each tick = 1 nanosecond)Clock cycle

Time can be expressed as a series of clock ticks a clock is the sequencing,
stepping mechanism which is the smallest unit in which a hardware event
can take place each tick of the clock is called a CLOCK CYCLE or period
a cycle is measured as some fraction of a second (1 us or 100 ns)

CLOCK RATE measures how many times a clock  ticks per second
a clock cycle is measured as the inverse of the  clock rate
1 hz is a single sine wave taking 1 second
if cycle = 1 second, rate = 1 hz

Speed
   milli = 1 / 1000       = .001
   micro = 1 / millionth  = .000 001
   nano = 1 / billionth   = .000 000 001
   pico = 1 / trillionth  = .000 000 000 001

A 100 hz clock is 100 waves in a single second with each cycle
taking .01 sec .  So, cycle=.01, rate = 100 hz

A 1 megahertz (1 mhz) clock ticks a million times per second
1 million hz is a million waves in a sec each taking .000001
or 1 microsecond

   .000     000     000      000
   milli   micro    nano    pico

   A 1 mhz clock has a 1/1million cycle = .000 001
   A 10 mhz clock has a 1/10million cycle = .000 000 100
   A 100 mhz clock has a 1/100million cycle = .000 000 010

Why slow clocks? Grace Hopper's nanosecond?