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Introduction to programmable computing devices
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Computer = Com + putare


Putare = to reckon
Com    = intensify

A computer is a "reckoning" or computing device.... 


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Computing devices:

	"Ancient" computing device: the abacus

	1822: Babbage's difference engine

Programmable devices:

	Programmable machine = a device which function can be 
				altered by a program 

	Mechanical piano/music box 
	Mechanical loom 

    Instruction encoding:    using HOLES !!!

    How to encode instruction using numbers:

	1 = add
	2 = subtract
	and so on


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Introduction to computer: storing instructions and information 
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Most common view (perception) of a computer (desktop computer)

Component of the computer by their functionality:

	Input devices
	Output devices
	I/O devices

	Computer System (the box)

Hardware and Software

	Hardware = the physical parts of a computer
	Software = the computer programs that you run with a computer



Logical view of a computer:

                                           I/O device
                                                |	
	Input   -----> Computer System -----> Output


	Compute System = CPU + Memory

	RAM memory: 
		Structure  (address, memory cell)
		Operation (Store, recall)                           - Calculator !


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Storing information in computer using numbers:

	Encoding = an agreement

	Everything inside a computer are stored as numbers

	Example:

		Computer instruction:    0 = add, 1 = subtract, 
				       and so on

		Sex info:  0 = male, 1 = female

		Marital status: 0 = single, 1 = married, 
			       2 = divorced, 3 = widowed

	$64,000 question:

		What does 0 represent ???

	Answer: context is needed to know what 0 represent !!!

	Just like:   You IS an English word. You is NOT used in the
		context of "Personal pronoun"





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The computer memory and the binary number system 
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A memory device must have more than 1 states

The electrical switch is a memory device: on / off

One switch can be in one of 2 states

	off = 0
	on = 1

N switches can be in 2^N states.



Representing numbers with switches:  binary number system


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Computer memory:

	1 switch = bit (BInary digiT)
	8 switches = byte

	Each byte is assigned a unqiue address 
		like SSN

	Adjacent memory cells can be combined to make
		larger memory cells:

	2 bytes = 16 bits
	4 bytes = 32 bits
	8 bytes = 64 bits


	We need larger memory cells due to "overflow"

	(demo program - Overflow *********************)


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Introduction to the computer: how a computer executes instructions 
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Structure of CPU

Operation of the CPU

Pointers

Program flow

Branching

Types of instructions that a computer can execute:

	Read/write memory
	Compute
	Branching

Entire programs consist of the 3 types of instructions !!!!





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Computer Algorithms 
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Algorithm = a step-by-step procedure for solving a problem 

Computer Algorithm:

        is an algorithm that can be executed by a computer


Difference between instructing Humans and Computer (Machine):

	A machine does not know how to remove a bulb

	Computers have no common sense knowledge (really dumb) 

A real life algorithm:    Tell them to use 2 pieces of paper and follow instructions

	Euclid Alg for finding Greatest Common Divisor.