(Remember: Digital vs. Analog) Digital systems have discrete values 1 / 2 / 3 / 4 / 5 On / Off Digital with two states is called Binary Analog systems have continuous data values
(Remember: Bits and Bytes) A bit (e.g., binary digit) is a single one (1) or zero (0). Eight bits is a byte – the standard grouping in digital electronics 1s and 0s can be used to represent: Numbers Letters Sounds Images Videos
INPUTPROCESS CPU Memory OUTPUT Input – Process – Output
INPUTPROCESS CPU Memory OUTPUT Storage This memory is volatile which means it requires electrical power to hold its value.
STORAGE INPUTPROCESS CPU Memory OUTPUT Storage Hard Disk (magnetic) CD/DVD/BD (optical) USB Flash (solid state) RAM Memory Main Memory Secondary Memory Storage
Main Memory vs. Storage Memory is volatile holds data and instructions temporarily Storage is nonvolatile contents retained when power is off
So why not use Storage hardware for Main Memory?
Solid State Storage (Storage 1 of 3) Flash memory resides on a chip (e.g., solid state; no moving parts; like RAM.) However, flash memory is nonvolatile so it retains its information when it is unplugged. A single 8GB USB/thumb/flash drive stores as much data as 1,000+ CDs Mini Memory Card
Magnetic Storage (Storage 2 of 3) A hard disk is the most common magnetic storage media, consisting of several inflexible platters covered with magnetic material enclosed in an airtight, sealed case. Hard drive platters spin at a rate of ~8000 RPM.
Hard Disk A head crash occurs when the read/write head touches the platter surface. Do NOT shake your machine while your hard drive is spinning. Clearance between head and platter is approximately two-millionths of an inch
Hard Disks A Redundant Array of Independent Disks (RAID) connects multiple disks into a single unit to achieve high levels of storage reliability.
Older magnetic storage media Floppy disks Tape drives
Solid State Drive vs. Hard Disk Drive Your next computer may have a solid state drive (SSD) instead of a hard drive. SSD Advantages: Faster (no spin start up, no moving head seek) Silent operation due to lack of moving parts Low power consumption Generate little heat Low failure rate SSD Disadvantages More expensive per gigabyte Great difference between write speed and read speed (may cause problems)
SSD (Solid State Disks) Many competing standards
Optical Media Storage (Storage 3 of 3) CD, DVD, Blu-laser Disc (BD) are all optical media that use a laser to read and write the data on the disc. Note: Magnetic disks are spelled with a K, and optical discs are spelled with a C.
Optical Discs How does a laser read data on an optical disc? laser diode prism light- sensing diode 0 1 lens pitland disc label Step 1. Laser diode shines a light beam toward disc. Step 2. If light strikes a pit, it scatters. If light strikes a land, it is reflected back toward diode. Step 3. Reflected light is deflected to a light-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0.
Optical Discs CD, DVD, Blu-laser Disc (BD) 1 CD =486 Floppy Disks 1 DVD =3,263 Floppy Disks 1 BD =17,361 Floppy Disks 1 CD =486 Floppy Disks 1 DVD =3,263 Floppy Disks 1 BD =17,361 Floppy Disks
Recent News Stories about Storage NSA Spy Center: Read more herehere White House Shares $200 Million Big Data Plan: Read more herehere 60 th Anniversary of Tape Storage: Read more herehere
(Remember: Prefixes) A byte is about the size it takes to store a letter of the alphabet. A kilobyte is about the storage you would need for a six-page paper. 1.44 megabytes: A floppy disk. 500 megabytes: CD-ROM 4.7 gigabytes: DVD Disc 25 gigabytes: Blu-Ray Disc 1 terabyte: All the X-ray films in a large technological hospital 10 terabytes: Printed collection of the U. S. Library of Congress 500 terabytes: All the information in all the books ever written 24 petabytes: Googles daily processing 500 exabytes: The worlds total digital content (as of May 2009). PrefixScale K (kilo)Thousand M (mega)Million G (giga)Billion T (tera)Trillion P (peta)Quadrillion E (exa)Quintillion Z (zetta)Sextillion Y (yotta)Septillion