THE VISIBLE COMPUTER

Hardware - physical part

Software - the instructions part

Firmware - hardware that contains software. Software instructions (semi) permanently programmed into Read Only Memory chips. Special kinds of ROM chips may also be reprogrammed. ROM BIOS – Read Only Memory Basic Input/Output System. Very A+

Input / Output (or peripheral devices) attach to the computer through a port. Shape, pin count and gender, purpose… very A+

Input - mouse, keyboard, scanner, microphone, trackball etc. Converts analog to digital.

Output - monitor, printer, speakers, video adapter, sound card, etc. Converts digital to analog.

INSIDE THE CASE

Circuit board that holds the microchips, interface cards and other interior components.

• CPU and slot / socket
• Bus lines - ISA VESA PCI (speed limits, lanes and control signals)
• Slots for memory - SIMMS and DIMMS - Primary storage
• Cache memory
• Mainboard BIOS to control basic hardware functions (video, disk, print) Flash ROM
• Power supply connectors
• System clock that doesn't tell time! (integrated into chipset)
• CMOS - holds system configuration (integrated into chipset)

Power supply

Supplies 12, 5 & 3.3 volts DC. Fan to exhaust air out of system

Secondary Storage

Controller / host adapter (probably integrated into mobo)

We need to talk about numbers!

• Because computer processing is based solely on numbers – native language of the machine
• Because computers use a different system then humans
• As a tech you will see (and possibly) need to adjust and adjust to these new kinds numbers
• How A-plussy? Explicit. Implicit.
• These numbering systems are simply other "languages" used to describe a quantity. You can count on this!

Decimal - our old friend…

• Base 10 - ten digits 0 - 9
• Humans love it
• Positional – each position has a " weight" each digit has "value"
• Take the number 1750 for instance…

For the curious or insanely compulsive… It’s all about a value times a weight!

1750 =

Do computers have fingers?

Binary It takes 00000010 to tango

Binary system 1’s and 0’s

No fingers, just electricity turned on and off

A binary number: 11000110

The equivalent decimal number: 198

• Fast?
• Unambiguous?
• Convenient?
• You be the judge.

The native language of the machine.  Good for computers, bad for their masters - uh, that would be us (for awhile at least...)

Now you’ll get this joke - "There are 10 kinds of people in the world. Those that understand binary and those that don’t"

Being able to set a SCSI ID via binary-based jumpers is very A+

Binary - Simple rules for a complex world?

Alone (or in small numbers) they are pretty cool. It's just when you put a whole bunch of them together…

A single binary digit is called a bit (or Binary digIT)

A nice binary "word" - 10000100100010010100111001000001

This particular binary word consists of 32 bits.

A byte is a group of 8 bits – this "word" consists of _____ bytes

For computers, lots of bits are cool. For humans they suck…

Hexadecimal

• Convenient shorthand for representing numbers inside of a computer – like computer memory addresses.
• Easy conversion – hex to binary and binary to hex
• Base 16 – now somebody gave us 6 extra digits.
• Hey what's up with this? Now there are letters in my numbers!
• A B C D E F

The hexadecimal system – sixteen digits. Computers like it, humans put up with it. Since a byte has eight bits, any multiple of eight works great. In print, you will often see Hex numbers designated by an h – like 1000h

Here is a megabyte represented in decimal: 1,048,576

Here is a megabyte represented in hexadecimal: 100000h

Let's count: 0 1 2 3 4 5 6 7 8 9 A B C D E F 10 11 12…

If you crave decimal and are really into "quantities":

Ah=10 Bh=11 Ch=12 Dh=13 Eh=14 Fh=1510h=16…

Remember (when the numbers increase)

• 9s always become As
• Fs always become 10s

Oh yeah, then what about this 1F, 20 stuff?

Step One	Step Two	Step Three
1F		20
Start with 1F	Increment. F becomes a 10 then carry the 1	Add the ones together and get 20

Do you feel the conversion?

Four bits is called a Nibble. Here is a table of the first 16 nibbles in Decimal, Binary and Hex.

Each row (on each side) of this table is the same value, just expressed in a different numbering system.

Hexadecimal was not built for easy decimal to hexadecimal conversions. However, it is superb for binary to hexadecimal conversions. We just need to nibble away at it.

A nice binary word - 10000100100010010100111001000001

A nice binary word revisited -

1000 0100 - 1000 1001 - 0100 1110 - 0100 0001

(you could use the chart (on the previous page) to identify the corresponding hex digits)

So by using hexadecimal, your basic 32-digit binary number can be shortened to 8489 4E41 - that's 24 less digits!!

A substantial savings for us bewildered human beings!

For the insanely curious…

Disclaimer: you do NOT need to know how to do this for this class…

COMBINING LITTLE DECISIONS TO MAKE BIGGER ONES

OK, now we have a seemingly infinite bunch of numbers. What about blue or the letter A?

We simply assign a number to a particular letter or color. If everybody agrees to this assignation or "standard" then we all see the same letters and colors on our computers.

ASCII - American Standard Code for Information Interchange.

ASCII, pronounced "ask-key", is the common code for microcomputer equipment. The standard ASCII character set consists of 128 decimal numbers ranging from zero through 127 assigned to letters, numbers, punctuation marks, and the most common special characters.

The Extended ASCII Character Set consists of an additional 128 decimal numbers and ranges from 128 through 255 representing additional special, mathematical, graphic, and foreign characters.

Bin	Hex	Dec	Char
01000000	40	64	@
01000001	41	65	A
01000010	42	66	B
01000011	43	67	C
01000100	44	68	D
01000101	45	69	E
01000110	46	70	F
01000111	47	71	G

BinaryVocabulary / quantities

Bit - single digit in a binary numbering system
Nibble - four bits / half a byte
Byte - eight bits treated as a unit
Kilobyte - 1024 bytes 2 ^ 10
Megabyte - 1,048,576 bytes 2 ^ 20 (or 100000000000000000000b) (100000h)
Gigabyte - 1,073,741,824 bytes 2 ^ 30
Zettabyte - 1,180,591,620,717,411,303,424 2^70
Yottabyte - 1,208,925,819,614,629,174,706,176 2^80

(note that a movement is afoot to designate binary vs. decimal bytes. In this scheme 1000 bytes equals a kilobyte and 1024 bytes equals a kibibyte. Same with mega, giga, tera, peta, exa…)