Memory, Storage and Media Flashcards
Primary Memory
- Main memory inside a computer
- Directly accessed by CPU, faster access than secondary storage
- both volatile and non-volatile
Random Access Memory (RAM)
- primary storage
- is a hardware device
- allows information to be stored and retrieved on a computer
- RAM is a volatile memory and requires power to keep the data accessible
- RAM normally has a larger capacity than ROM
Read Only Memory (ROM)
- primary storage
- is a hardware device
- Stores basic start up instructions for a computer e.g. basic input/output system (BIOS)
- Stores bootstrap loader -ROM contains nonvolatile data, meaning it keeps it data even if the device loses power
- Data can be read from and written to RAM, ROM can only be read from
Secondary Storage
- non-volatile, persistent memory that is accessed by a device that is part of computer
- not directly accessed by the CPU
Hard Disk Drive-HDD
- secondary storage
- HDD is an electromechanical data storage device that uses magnetic storage
- to store and retrieve digital information using one or more rotating magnetic disks
Solid State Drive(SSD)
secondary storage
Device that stores data by controlling the movement of electrons within a microchip;
there are no moving parts hence more durable
-Has faster random access
-Has a quick start up/shut down time (reduced latency)
-Is very small
-Is very light
-Consumes very little power
Why SSD is replacing HDD
- lower/less power consumption/more energy efficient
- runs quieter
- data access is faster
- occupies less physical space/more compact
- lighter, so more suitable for a portable computer/laptop
- no moving parts so more reliable/durable in a portable computer/laptop
Why many web servers still use HDD technology
-HDD is cheaper for larger amounts of storage space
-HDD has greater longevity for read/write functions
`-HDD are trusted technology -No requirement for the increased speed of SSD
Offline Storage
- non-volatile memory that can be removed from a computer system
- must be physically connected to computer to obtain stored data
- used to store files as a backup
CD(Compact Disk)
- offline storage
- Small plastic disc on which music or other digital information is stored
- in the form of a pattern of metal-coated pits from which it can be read
- using laser light reflected off the disc
Digital Versatile Disk(DVD)
- offline storage
- Optical storage media that uses a single spiral track
- uses dual layer technology, allowing high data storage capacity
Digital Versatile Disk RAM (DVD-RAM)
- offline storage
- Optical storage media that uses concentric tracks
- allowing writing and reading to take place at the same time
External SSD
- offline storage
- similar to internal SSD except it can be easily removed after data has been copied
- connected to computer via USB port while internal SSD is connected via SATA controller
Blu-ray
- offline storage
- Optical storage media
- has high storage capacity by using blue laser technology
Flash Memory
- offline memory
- Nonvolatile memory chip used for storage and for transferring data
- between a personal computer (PC) and digital devices
- It has the ability to be electronically reprogrammed and erased
- It is often found in USB flash drives, MP3 players, and digital cameras
How is digital Media Read and Written in Optical Media
- Red laser is used (blue in case of Blu-Ray), shines onto surface of the disk
- It is rotated at a constant speed to be read
- Surface is covered in a track that spirals from the center
- Data is represented on the surface using pits and lands
- Pits and lands represent binary values
- Pits reflect light back differently to the area in between/land
- Optical device can determine the binary value from the light reflection
How is Data Written and Read in Magnetic Media
- surface of magnetic disk/tapes are coated with millions of iron particles
- allowing data to be stored on them
- the surface is divided into concentric tracks, which save data on them
- each track is sub-divided into sectors
- the particles act as magnets when they are exposed to a magnetic field
- magnetic disk/tapes contain read-write heads
- they contain electromagnets that generate magnetic fields
- in the iron particles, as the head passes over them
- a magnetic field’s pull means a binary 1 and a 0 otherwise
- while reading, read-write heads have no magnetic field
- storage medium charges the magnet in head
- causes a current to flow through head based on the polarity
- this way data is sent from read-write heads into the memory
How is Data Read and Written in Solid State Media
- store data by controlling the movement of electrons
- within NAND chips -use of NAND only allows to read or erase a block of data at a time
- The data is stored as 0s and 1s in millions of tiny transistors within the chip
- This effectively produces a non-volatile rewritable memory
- also use Electronically Erasable Programmable Read-Only Memory (EPROM)
- main difference is that it uses NOR chips than NAND making operations faster
- EPROM allows data to be read or erased in single byte at a time
To calculate file size whose resolution is n x m pixels with w as the colour-depth
-multiply n and m
-multiply product with w color-depth and divide by 8 -convert the answer to kB/MB/GB/TB
(n x m) x w / 8
-to convert the answer from bytes to Kilobytes, divide it by 1024
-to convert the answer from bytes to Megabytes, divide it by 10242
-to convert the answer from bytes to Gigabytes, divide it by 10243
