2- Bits, Bytes and conversions

ASCII

ASCII table

assembly language instructions

Because 0s and 1s are hard to comprehend, programmers soon created programs called assemblers to automatically translate human readable instructions

decimal numbers ("dec" refers to ten)

Because early humans represented values using ten fingers, humans developed base ten numbers, known as decimal numbers("dec" refers to ten)

Bits and Bytes

Computers are built from connected switches that, like light switches, are either on or off. On is called 1, and off is 0. A single 0 or 1 is called a bit. 1011 is four bits. Eight bits, like 11000101, are called a byte.

machine instructions

Instructions represented as 0s and 1s

A character

is a letter, symbol, or single-digit number. Each character can be given a unique bit code.

ASCII (American Standard Code for Information Interchange)

is a popular code for characters developed in 1963. ASCII uses 7 bits per code and has codes for 95 characters. Ex: Using ASCII, the letter Z would be stored in a computer as 1011010 (shown below as 101 1010; the space is just for readability in this material). Each bit code is sometimes written as an equivalent decimal number.

Unicode

is another character encoding standard, published in 1991, whose codes can have more bits than ASCII and thus can represent over 100,000 items, such as symbols and non-English characters.

hexadecimal (or hex)

means a base 16 number. Each digit is an increasing power of 16: 160, 161, 162, etc.

Octal

means a base 8 number. Octal is sometimes used as a compact binary representation because three bits can be represented as one octal digit, though hex is more common. The eight symbols for an octal digit are 0, 1, 2, 3, 4, 5, 6, 7.

high-level languages

programming languages whose instructions more closely resemble the English language

compilers

programs that automatically translate high-level language programs into executable programs.

how many bits in 101100

6

memory vs processor

The processor computes data, while the memory stores data and the instructions

a 0 or a 1 is called

a bit

8 bits are

a byte

an executable program

a sequence of machine instructions together form

binary numbers ("bi" refers to two)

computers can only represent two values (0 or 1), so use base two numbers, known as binary numbers ("bi" refers to two)