Bit

binary digits made up of 1s and 0s

Boolean Operations

operations that manipulate true/false values

Gates

Can be constructed from a variety of technologies such as gears, relays, and optic devices.

In computers, gates are usually implemented as small electronic circuits in which the digits are 0 and 1 are represented as voltage levels

AND Gate

The multiplication gate

0 0 = 0

0 1 = 0

1 0 = 0

1 1 = 1

NOT Gate

Oposite Gate

0 = 1

1 = 0

OR Gate

The Adding Gate

0 0 = 0

0 1 = 1

1 0 = 1

1 1 = 1

XOR Gate

Exclusice or

0 0 = 0

0 1 = 1

1 0 = 1

1 1 = 0

Flip-Flop

Hexadecimal Notation

A shorthand notation that uses 4 bits to produce a table displaying 16 different characters.

0 0 0 0    0

0 0 0 1    1

0 0 1 0    2

0 0 1 1    3

0 1 0 0    4

0 1 0 1    5

0 1 1 0    6

0 1 1 1    7

1 0 0 0    8

1 0 0 1    9

1 0 1 0    A

1 0 1 1    B

1 1 0 0    C

1 1 0 1    D

1 1 1 0    E

1 1 1 1    F

Main Memory

Kilobyte

2^10 ≈ 1024 bits

Megabyte

2^20 ≈ 1 million bits

Gigabyte

2^30 ≈ 1 billion bites

Memory Module

A large group of bytes that supports

1) Addressing

2) Read

3) Write

Least Significant Bit

The right most bit in any unique bitstring

Most Significant Bit

The right left most bit in any unique bitstring.

Also represents the numeric value

Nibble

4 bits = 1 nibble

Hexidecimal notation

Mass Storage

Advatages of Mass Storage over Main Memory?

Mass Storage includes volatility, large storage capacities, low cost, and in many cases, the ability to remove the storage medium from the machine for achival purposes.

Magnetic Disk

Disadvantages of Mass Storage

They typically require mechanical motion and therefore require significantly more time to store and retriece data than a machine's main memory, where as all activities are performed electrnically.

Delays of Reading & Writing

1) Seek Time: the time required to move the read/write heads from one track to another

2) Latency Time: half the time required for the disk to make a complete rotation, which is the average amount of time required for the desired data to rotate around to the read/write head once the head has been positioned over the desired track

3) Access Time: the sum of seek time and rotation delay

4) Transfer Rate: the rate at which data can be transferred to or from the disk

Optical Systems

Include CDs, DVDs, CD-Rs, CD-RWs

Information is recorded on them by creating variations in their reflective surfaces.  This information can then be retrieved by means of a laser beam that monitors irregulatities on the reflective surface of the disk  as it spins

RAM

Random Access Memory

The ability to access cells in any order in a computers main memory

ROM

Read Only Meomory

Memory whose contents can be accessed and read but cannot be changed

WORM

Write Once Read Many

WMRM

Write Many Read Many

What does ASCII stand for?

American Standard Code for Information Interchange

What is ASCII?

This code uses bit patterens of length seven to represent the upper and lowercase letters of the English alphabet, punctuation symbols, the digits 0-9, and certain control information such as line feeds, carrige returns, and tabs

Why is ASCII important?

ASCII is a character set, not a language. It helps in the process of allowing symbols represented on your keyboard to be printed on the screen.  These codes are standardised so they can work on different computers.

Base 2

Binary System

Digits Include [0, 1]

Base 2 Example:

What is 11 in Base 2?

(1x8) + (0x4) + (1x2) + (1x1) =

8 + 0 + 2 + 1 =

11

Base 10

Decimal System

Digits Include [0,1,2,3,4,5,6,7,8,9]

Base 10 Example:

What is 5,123 in Base 10?

(5x1000) + (1x100) + (2x10) + (3x1)=

5000 + 100 + 20 + 3=

5,123

 Decoding from Base 2 to Base 10

128  64  32  16  8  4  2  1

Step 1: Start at least sig bit (far right) # about the bits from 1, doubling as you go.

   1    0    0    1    1    1 

32 + 0 + 0 + 4 + 2 + 1

Step 2: Add all numbers from 1 that sit a 1 as the binary number

= 3910

Decoding from Base 10 to Base 2

2510

32  16  8  4  2  1

                    1  1  0  0  1 = 25

Binary Addition Table

  0            0             1           1            1

+ 0         + 1          + 0        + 1            1

-------     --------      -------     ------       + 1

       0            1             1           1        ---------

                                                           11

   1 1 1 0

 +1 0 1 1

   -------------

    ?

1 1 0 0 1

16 + 8 + 0 + 0 + 1 = 25

Check: 1110 = 1410

              1011 = 1110

14 + 11 = 25

2's Compliment

This system uses a fixed number of bits to represent each of the values in the system.

What is 11100010 compliement?

00011110

What is the left most bit in any bit string represent?

 The sign value

0 = +

1 = -

Positive numbers are just binary

Negative numbers are 2's Compliment

Data Compression

To reduce the size of the data involved while retaining the underlying information

Parity Bits

A bit that is used in an error detection procedure in which a 0 or 1 is added to each group of bits so that it will have either an odd number of 1's or an even number of 1's.

If the parity is odd then any group of bits that arrives with an even number of 1's must contain an error.

Hamming Code

Hamming Distance

The number of bits by which two n-bit vectors differ.

For example, the Hamming distance between 001101 and 001110 is 2.

Sample Point (Image)

Sample (Image)

Sample Rate (Image)

The number of samples taken (per second)

Pixel

A point that we have control over its color

Resolustion

The number of pixels in a digital photo is commonly referred to as its image resolution

r x c = # of pixels

Color Depth

The size of a pixels representation (in bits or bytes)