There are four main drives for the computer, all of which are classed as core hardware components. Each one uses a different way to store data and each one has different data, read/write, speeds.
The Floppy Disk used to be the number one storage media until the CD, DVD, USB Flash Disk (Memory Disk) and USB Hard Drive arrived on the scene. In order to store data (i.e. files) onto a floppy disk you need a Floppy Disk Drive. It has the job of reading (looking at) data and writing (storing) data to/from the floppy disk.
Although the floppy disk drive and floppy disk are virtually obsolete now, due to them being classified as slow (in comparison to other storage technologies) and having a small storage capacity (1.44 MegaBytes or 1,457,664 Bytes), they can still be used to store valuable, backup data, files (such as Letter and CV Templates). Some computer fairs (markets) still sell the floppy disk drive for around £16 and a box of 20 floppy disks for around £5.
The CD (Compact Disk) was the replacement media for the floppy disk, but is now becoming obsolete itself. In order to read data from a CD you need a CD Player and in order to write data onto a CD you need a CD Recorder.
All CD Drives have a CD Player built into them as standard, and many have a CD Recorder built into them too, but with the price between them being as small as £5 many retailers no longer sell the cd player only. They only sell the combination (cd recorder and cd player). A CD Player, also known as a CD ROM, allows an application to read data from a CD and then interpret it as Music and/or Data files. A CD Recorder, also known as a CD Burner, does the same as a CD Player but it also allows an application to record Music and/or Data files onto a CD.
A CD Recorder can use either a CD-R or a CD-RW compact disk to store data on. There are CD+R and CD+RW compact disks out there but they are not as widely used as the CD-R and CD-RW varieties. Regardless of the type of cd used; One cd can store up to 700MB of data on it, either in one go or in multi-sessions (bits at a time). The main difference between the CD-R and CD-RW is that the CD-RW can be formatted (erased/blanked/wiped) so it can be re-recorded on whereas the CD-R cannot be formatted at all and so cannot be re-recorded on. However, do not think the CD-RW is better because it's not. It is limited by speed.
A CD-R can have data recorded onto it at a maximum speed of 52x, but a CD-RW can only have data recorded onto it at a maximum speed of 12x. In general a CD-R is good for storing permanent data and a CD-RW is good for storing temporary data. As a rule you should always backup (record) your important documents and files onto a CD for safe keeping, as you never know when you will accidentally delete a document or file from your hard drive for example.
With regards to maximum speeds, if you see something like 52x 32x 52x on the box of a CD-RW (CD Re-Recorder and CD Player) for example the Xs mean the Write, Re-Write and Read Speed. So a CD-RW with 52x 32x 52x speeds means the CD-RW can Write (Record) data onto a Blank CD at 52 maximum speed, Re-Write (Re-Record / Record Over) data onto an Already Recorded On (or Blank) CD at 32 maximum speed and Read (Playback) data from a CD at 52 maximum speed.
The speeds themselves can be measured in KB/Second or MB/Second. 1x speed is 1.32MB Per Second, so 8x speed is 10.56MB Per Second (8 x 1.32). In reality though the maximum speeds might never be reached as the burning (copying) process works by gradually picking up speed as it records and plays back. So the CD-RW might of recorded or played back the data before the maximum speed was reached.
One thing to note about CD Recording is that you need a certain CPU, a certain amount of Memory and a certain amount of Hard Drive space before you can record. The reason for this is because if you copy some files from your hard drive onto a CD the CD Recording application does not normally do a straight copy. It does not copy each file from the hard drive onto the CD. What it does instead is buffer them. This means if you have 600 files to be copied onto a CD, at 1MB each, it creates a buffer-file of 600MB that contains a copy of the 600 original files to be copied. The buffer-file is stored on the hard drive. Once this stage is out the way the CD Recording application then starts copying the buffer-file onto the CD, copying a little piece at a time into Memory before transferring it onto the CD.
One of the main reasons a CD Recording application uses memory, instead of just copying the data straight onto CD, is so that it can check the data for errors before copying it to CD. The more memory a computer has the better the CD Recording application performs, as it can copy more data into memory for example. Another thing to note is that although a CD states 700MB on the cover that number refers to your data plus the data used by the CD Recording application, which it needs to use for its own recording purposes. So really you should knock off about 50MB and say 650MB is for your data.
CD Players with playback speeds of 8x up to 32x are obsolete. Today's average playback speeds are 48x and 52x. A CD Recorder should be in the region of 52x (CD-R Recording speed), 32x (CD-RW Recording speed) and 52x (Playback speed) - With a CD Recorder it depends on a CD's ability to playback and record at a certain speed as to whether or not the CD Recorder can actually match the speeds it claims it can perform.
The DVD Drive is now one of the core hardware components for the computer, and more precisely the Combo (Combination Drive) is the core hardware component. A Combo consists of a CD Player, CD Recorder, DVD Player and DVD Recorder all-in-one unit (casing). You can still buy these components separately but these days people tend to buy the Combo, because the price works out better.
DVDs are exactly the same as CDs except they store more data and are geared towards storing media such as Photograph Albums, DVD Movies and so on. They come in four formats: DVD-R, DVD-RW, DVD+R and DVD+RW. The DVD Drive and DVD work in the same way as a CD Drive and CD as explained above. The DVD can store up to 4.7 GigaBytes of data and up to 8.5 GigaBytes on double layered DVD Drives (Double Layer is like Long Play on a VCR). DVD Players with a built in CD Player and CD Recorder too should have the following kind of speeds.
(DVD+R Double Layer)
With both CD Recorders and DVD Recorders you should always go down one or two speeds when recording, otherwise the recording might fail (buffer underrun). This is because the amount of data the recording application needs to record in one go might not of been stored (buffered) in time, due to the hard drive being too slow to gather the data for example. A file on your hard drive can be split into two pieces for example if it cannot fit into one complete space on the hard drive. When a recording application needs such a file the computer first puts the two pieces back together to make one complete file. This takes time. Time which could be too slow for a recording application.
A recording application needs to be fed a continuous amount of data for it to work. If it does not get that data in time bad things happen, like data corruption and so on. In other words, it might fill the CD or DVD with spaces instead of data because the spaces were not filled in with data in time. By slowing down the recording speed you are giving the recording application extra time to wait for data to be copied/filled in.
Fig 1.6 The Flash (Memory) Disk
The Flash Disk - also known as a Flash Pen (because of its pen-like looks and small size), Flash Memory (because it is a piece of hardware that uses flash memory) and Flash Drive (because it creates a logical Drive on the computer) is one of the best gadgets around. It allows you to permanently store your data (files) onto the flash memory chip, so that even when you turn off the computer the data is still on the flash disk.
The beauty of the flash disk is its storage capacity and portability. It is portable not just because it's so small but also because it plugs into a USB Port (Socket),
therefore making it portable (pluggable) between computers - Anywhere you take it just plug it into a computer's spare USB port and then look at your files. You can
delete files, save files and so on in the same way as you can with a hard drive or floppy disk.
The storage capacity ranges from 4 GigaBytes to 64 GigaBytes these days (4GB, 8GB, 16GB, 32GB and 64GB), but OS X (El Capitan or Sierra) will probably use 2MB or so to initialise the flash disk (depending on the flash disk and the file format/system used). The rest of the memory though will be yours to use. Current prices, from a computer fair or cheap retailer, are approximately £4 (4GB), £8 (8GB) and £14 (16GB).
With technology and prices changing every 3 months or so you will probably find your computer has all the drives and drive capacity you need. Meaning, you will probably not need any of the above drives internally. The MacBook Air Laptop computer is evident of this. However, all of the above drives are now in external USB format which means it's now an affordable/wise option to buy a flash disk for example if you work on different computers from your home and/or workplace for example.