RAM/ROM and Storage (1.1.3)

RAM (Random Access Memory)

RAM is used to store data that is being frequently accessed from secondary storage. The reason RAM is used for this is due to the immense speeds that RAM has, although it's not used as secondary storage as it is voletile.

The data that will get stored in storage blocks, these blocks are given a numeric value which is it's memory address. Within memory, there are only a certain number of blocks that can be allocated based on the size of the RAM.

A block has a fixed size. The first block in memory will be given the ID of 0, and it increases as it goes on. For example, if a computers RAM had a capacity of 1GB, it would be able to support 270,000,000 memory addresses.

Here is an very small example of how data is stored in RAM

Address	0	1	2	3	4	5	6	7	8	9	10	11	12	13
Data	P	R	O	J	E	C	T		V	O	L	T

The typical cost for 16GB of DDR4 Ram can be aout £15, with a single GB of DDR4 RAM being about £1.06/GB.

ROM (Read Only Memory)

ROM is different to RAM. ROM is Read-Only and can't be overwritten.

On ROM, the systems bootloader, BIOS and other essential software that is used to begin the start-up and hand-over to the OS. Within the BIOS, the ROM doesn't store the values of the settings that you change, they are stored using CMOS (which is voletile but powered using a little battery).

So if the user were to change the boot order from booting from their main hardrive to a USB named "go to baileyq.me", that would be stored in CMOS and not ROM. ROM would only store that there is a settings key that is for boot order.

Optical Storage

Optical Storage is a type of secondary storage where a laser is used to read and write data. A typical example of optical storage would be a CD or a DVD. Data is burnt onto them using a laser, making them write-once read-many. So if you were to burn "play factorium.org" onto a disk, you would no longer be able to change it and the disk will forever say "play factorium.org". Typically they are regarded as a slower form of storage.

The average price per GB of Optical Storage is approximately £0.035.

Magnetic Storage

Magnetic Storage is a type of secondary storage that uses a magnetisable coating on a disk. On the surface of the disk, small magnetised dots are mate, these dots are then read and erased by small electromagnets. The most common example of this is a HDD (Hard Disk Drive). In HDDs they have a read/write head and it sits nanometers aboe the disk and uses the magnetic field of the disk to read or edit data. Another example of Magnetic Storage is magnetic tape.

So if you wanted to write "OCR2.org.uk is better than OCR.org.uk", a write head would create small magnetic dots using the magnetic field of the disk. Then if you wanted to read it, the same head woud go over where the dots are and use the magnetic field to read it.

The average cost per gigabyte of a HDD is £0.029.

Solid State Storage

Solid State Storage is a type of secondary storage that uses flash memory to store data.

Flash memory is part of the EEPROM family, meaning Electroniclly Erasable Programmable Read Only Memory. Two transitors are seperated by a thin oxide layer, one of the transistors is known as a floating gate, the other a control gate. Using this they trap electrons in and use that to store data. This type of storage is non-voletile. Although they use transistors and cells, they don't have any moving parts.

So if you wanted to store a text file that said "aqa2.org.uk > aqa.org.uk", the SSD would use flash memory and the data would be stored using transistors and trapped electrons.

One issue with flash storage is that there is only a certain amount of writes that it can do before there starts to be issues that arrise such as not being able to read or write data.

The average cost per gigabyte of an SSD is £0.06

Virtual Storage

Not to be confused with Virtual Memory, Virtual Storage can also be known as Cloud Storage. This is where data is stored in a shared-pool on servers with other users. This is useful as it can be accessed at any time, and users don't have to deal with the upkeep and maintinence of the drive if anything happens. However they don't have control over the safety of their data, so they are trusting the cloud provider with their data and hoping that they have adequite security. Another disadvantage is that you typically have to pay per month per gigabyte.

The average price per gigabyte of cloud storage £0.0073

It can also be know as abstraction/seperation of logical storage from physical storage. An example of this is if there is a network drive and a student logs into a computer on the network and accessed their files on this drive, the pupil will percive that they have a whole drive on the network, whereas their "drive" is actually just a folder on a larger drive.

Sources:

• https://diskprices.com/?locale=uk&condition=new,used&units=gb&disk_types=bdrw,bdr,dvdrw,dvdr,cdrw,cdr

• https://computer.howstuffworks.com/flash-memory.htm

• http://youtube.com/watch?v=fmWr7gTxErA&list=PLCiOXwirraUCQZhirOWfj3ZnkxBnSpq6w&t=3s