# ECS 36A Lecture Notes - Lecture 2: 3I, Endianness, Binary Number

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Published on 3 Oct 2018

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ECS 36A - Lecture 2 - Bits and Bytes at Work

Bit vs Bytes

● Bit -- most basic unit of data

○ Comes in only 2 states

● Byte = 8 bits = 2^3 bits (base 2)

How many bits do you need to represent 52 different things? Log2 52 < 6

Question of interest -- WHY are we interested in powers of 2? -- it is in relation to the reason

that memory also comes in powers of 2

Memory has 2 states = 0 or 1 (binary), and the # of states storable are categorized by a power

of 2 -- which is why the power of 2 has special meanings in computer science and is a really

important aspect

In most, contemporary cases, bytes have become the most common, basic unit of information

over bits because of convenience (terms of how much storage it has)

Prefixes are used to represent larger amounts of bytes:

Decimal- based notation

● k: 1,000 (10^3) bytes -- k is lowercase while others are uppercase

● M: (10)^6

● G: (10)^9

● T: (10)^12

Binary notation

● ki: 2^10

● Mi: 2^20

● Gi: 2^30

● Ti: 2^40

Examples:

1. Convert the number 12 to binary.

#12 → 8+4 : break up the number 12 and proceed to convert the 2 parts of the equation into

binary and add

1000 +100 = 1100

The first 1 in 1100 is the Most significant Bit and the Last 0 in 1100 is least significant bit