Information Technology Ch. 3

hexadecimal numbering system

0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 A 11 B 12 C 13 D 14 E 15 F 16 10 ..... 26 1A

netmasks

An IP address has two components, the network address and the host address. A netmask separates the IP address into the network and host addresses (<network><host>). We perform netmask operations on these addresses, for instance to pull out the network number (the first 3 octets) or the machine number (the last octet)*

unsigned binary

An unsigned binary integer is a fixed-point system with no fractional digits.

EBCDIC

EBCDIC, only used in IBM mainframes, used 8 bits giving 256 different patterns

Unicode

Unicode uses 16 bits for 65356 patterns! This allows us to store the characters in every alphabet as well as a large number of symbols

decimal

primary human number system

vigesimal

used by pre-columbian mayan civilization just google it mydude

NOT

0 = 1, 1 = 0

powers of two lmao

2^0 = 1 2^1 = 2 2^2 = 4 2^3 = 8 2^4 = 16 2^5 = 32 2^6 = 64 2^7 = 128 2^8 = 256 2^9 = 512 2^10 = 1024 (this value is often referred to as 1K, K for kilo) 2^11 = 2048 2^12 = 4096 2^13 = 8192 2^14 = 16384 2^15 = 32768 2^16 = 65536 ... 2^20 = 1048576 (1 M, or mega, which is a little over 1 million) ... 2^30 = 1073741824 (1G, or giga, which is a little over 1 billion)

Given a number of bits, know how to determine the number of different values that can be stored

8 bits - 255 2 complement (8bit) - -127 to 128 N bits = x 2 complement n bits = -x/2^2 to x/2^2-1

ASCII

ASCII is the most common character representation we use 7 bits so that we have 2^7 = 128 different patterns we use these 128 patterns to store 52 letters (both upper and lower case) 10 digits punctuation marks a variety of other symbols and control character Note: even though ASCII only uses 7 bits, a character is still stored in 1 byte, so 1 bit is not used

bit-wise operations

Bit-wise means that we apply the operation to two bits at a time (except NOT, which is applied to a single bit) (except NOT)

bitmap

Bitmaps are the most common way to store image files

how to convert both unsigned and two's complement binary numbers into decimal and from decimal to unsigned or two's complement binary

Continuously divide the decimal value by 2 recording the remainder until our decimal value is 0 The collection of remainders, written in opposite order, is our binary number or Add the numbers

why we use binary in computers.

Everything is stored or controlled using high current or low (no) current, so we have only two states for everything the computer does The simplest storage location in a computer is of a single bit

XOR

Exclusive or or exclusive disjunction is a logical operation that outputs true only when inputs differ (one is true, the other is false) so 1 and 0 = 1

the difference between how black and white and color images are stored.

In a black and white image file, each pixel is stored as 1 bit indicating if the pixel is on/white (1) or off/black (0) For a color image, we store each individual pixel using 3 bytes, each byte storing the percentage of red or green or blue in the color

converting two's complement numbers from positive to negative or negative to positive

In two's complement, the leftmost bit becomes the "sign bit" indicating the number's sign, 0 for positive, 1 for negative For positive numbers, there will be no change (our largest positive is now 127 which is 01111111 since we only use 7 of the 8 bits for the number with the 8th bit being the sign) For negative numbers you must first convert from negative to positive to see what the number is

how the jpg and gif formats reduce storage

JPG and GIF formats throw out some of the details to reduce the image's size to about 1MB using lossy compression

network addresses

The Internet Protocol (version 4), used in all network computers, dictates that every computer will receive a 32-bit address divided into 4 octets Each octet will store an 8 bit positive number giving a range of 0 to 255

AND

both bits must be 1 to = 1

binary

digital computers use binary, 1/0

2's complement

for zero, use all 0's. for positive integers, start counting up, with a maximum of 2(number of bits - 1)-1. for negative integers, do exactly the same thing, but switch the role of 0's and 1's (so instead of starting with 0000, start with 1111 - that's the "complement" part).

hexadecimal

groups of four binary digits create a hexadecimal digit, used in computer related disciplines to make binary more readable, easier to read than octal, but more complex because of the inclusion of digits A-F

octal

groups of three binary digits create an octal digit, used in computer related disciplines to make binary more readable

unary

not common, 0

OR

one bit must be 1 to = 1

how images can be stored in bitmaps

stored in a grid by bits or bytes per pixel

cuneiform

used by the ancient babylonians