How Data is Stored
When we group bits together they have been given names by the computer industry.
Most references to computers use the number of bytes as a measure for the computer's memory (primary storage) capacity and storage (secondary) capacity.
Computer memory is partitioned (divided) into a number of data containers called memory cells
Each cell stores a specific amount of data called a word (e.g., in our class, we will usually use examples using 8 bits.)
Each cell has an associated location identifier called an address
Data to be processed is coded in a binary (base-2 number) form using various encoding schemes discussed below:
To begin with, digits 0 and 1 are binary digits and each is referred to as a bit for short.
Again, 0 represents an OFF state and 1 represents an ON state
Given nbits contained in a cell, there are 2^{n} (read "2 to the power or n") ways in which zeros and ones can be arranged, e.g. given 2 binary digits (either 1 or 0), arrangements may be one of four (2^{2} or 2x2 or 4) possibilities - 00, 01, 10 and 11.
The capacity of a computer's memory is determined by the number of bits per cell and the number of cells into which memory has been partitioned, i.e., computer memory depends on how many bits may be stored in each cell and how many cells there are available.
The industry settled on a sequence of 8-bits (given the unit name byte) as the basic unit of memory
The term byte preceded by a prefix are used to express the memory/storage capacity of a computer. See Chart #1 below.
Units for Measuring Memory (Data Storage) Capacity:
1 Bit |
= 1 Binary Digit |
4 Bits |
= 1 Nibble |
8 Bits |
= 1 Byte |
2^{10}= 1024 Bytes |
= 1 Kilobyte |
2^{20} = 1024 Kilobyte |
= 1 Megabyte |
2^{30}= 1024 Megabyte |
= 1 Gigabyte |
2^{40}= 1024 Gigabyte |
= 1 Terabyte |
2^{50}= 1024 Terabyte |
= 1 Petabyte |
Why is this significant? (Refer also to the basic functions of a computer from a previous reading.)