Computer Hardware 

Instruction fetch cycle in a computer:
#--------------------------------------
# IR - 	Instruction register, CPU memory 
#	cell that holds the instruction 
#	currently executing.  All 
#	instructions perform a single, 
#	small, well-defined task.
# PC -	Program Counter, address in 
#	memory of where the next 
#	instruction to execute is stored.
#
WHILE (forever)
	{
	IR <- Mem[PC]	
	PC <- PC + 1
	Execute IR
	}

# Pieces of a Computer:
	CPU: executes instructions
	RAM Memory: fast, volatile 
	ROM Memory: fast non-volatile
	I/O Devices:
		Keyboard
		Mouse
		Printer
		CDROM/DVD
		Secondary Storage 
		(not "Memory"):
			Hard Disk
			Memory Stick
		Network adapter

# Types of Instructions:
	Calculate a value
	Store a value in memory
	Input/Output 
	  (move values to or 
	   from I/O devices)
	Change PC (loop, branch)

# The computer is not intelligent, it
# can execute very simple sinstructions.
# The intelligence in computers is
# achieved by human beings being able 
# to express complex processes in terms 
# of simple computer instructions. 

 Operating System 
Program: A set of instructions
Process: A program that has been copied
	into memory is being executed

Multi-processing
CPU executes one instruction at a 
time.  CPUs are "timeshared" so 
it appears multiple programs are 
executing concurrently (think of a 
chess grandmaster playing hundreds
of chess games at the same time)

An operating system is software.  

Operating Systems Functions:
	1. Provides a "simple" interface 
	   for performing I/O.
	2. Controls the multipprocessing
	3. Organizes the secondary storage 
	   into a "file system"
	4. Fetches programs from the file
	   system into memory and starts 
	  them executing (makes them processes).
		a. Command line interface
		b. Window interface

 File System 
* Files and Directories/Folders (mostly)
* Folders form tree-structured storage 
  organization (but not really)
* Full Pathname
* Current/working directory and 
  Relative Pathname
* Users and Permissions
	a. Administrator
	b. Limited Account
* File Types
	a. Files contains 1s and 0s
	b. Programs choose how to 
	   interpret those binary values
		i. text
		ii. Word Processed
		iii. Image
* Determining File Types
	a. By content
	b. By filename
* Network File System
	a. Network Computer System Names:
		nwdata1
		pluto
		stu.cs.jmu.edu
	b. Mounting
		Single pruned tree
		Separate Drives
* WWW (specialized network file system)
	a. Read-only
	b. URLs