Traditionally, the main storage device of the personal computer is the hard disk drive (“HDD”). Newer, solid-state drive (“SSD”) technology is slowly becoming more affordable and accordingly more popular, especially in laptops. Storage is persistent, unlike memory which is volatile.
In this post:
Storage devices store data using one of the following 3 media:
Previous knowledge:
1. Magnetic
1.1 HDD
Data is stored magnetically on metal platters inside the HDD. The storage capacity is measured in megabytes, gigabytes, and terabytes.
HDD connect to the motherboard using one of the following connections:
- Integrated Drive Electronics (“IDE”)
- Serial Advanced Technology Attachment (“SATA”)
There are lesser-known interfaces, for example, SCSI, which are not in the syllabus.
1.2 Magnetic Tape
In the early days, computer data was primarily stored magnetically on tape. Early computer hobbyists no doubt have fond memories of loading programs from cassette tapes and later floppy disks.
2. Digital
Digital storage is physically similar to RAM. It has fast access speeds and is generally very robust as there are no working parts. They also consume less power and accordingly do not heat up significantly.
2.1 Pen drive
The pen drive, also known as a USB memory stick or USB Flash drive has largely replaced optical storage media. They are highly portable and extremely rugged, having no moving parts.
Learn how to format a USB drive in the How to format a USB drive tutorial.
2.2 SD Card
Secure Digital (“SD”) cards are used in a variety of mobile devices such as smartphones & digital cameras.
2.3 SSD
Solid State Drives (“SSD”) hold several advantages over traditional HDDs.
- Faster read/write speeds
- Lower power consumption (less battery drain on laptops)
- Zero vibration
3. Optical
All three optical media work in a similar fashion, which is data is read from a disc using a laser.
3.1 CD
A Compact Disc (“CD”) is an example of an optical storage medium. Patterns are burned into and read from the layer of shiny material under the plastic surface of the CD by a laser.
3.2 DVD
A Digital Versatile Disc (“DVD”) is the second example of an optical storage medium.
A CD– & DVD-ROM look and operate identically.
3.3 Blu-Ray
A Blu-Ray disc has an even higher storage capacity than a DVD.
4. Comparison
| Property | CD | DVD | Blu-Ray |
|---|---|---|---|
| Disc coating | Hard | ||
| Capacity | 750 MB | 4.7 GB (single layer) 8.5 GB (dual layer) | 25 GB (single layer) 50 GB (dual layer) |
| Laser | Red | Red | Blue |
| Laser wavelength | 780nm | 650nm | 405nm |
| Suited to | Music; data | Standard quality video | HD video |
| Can read CD | ✓ | ✓ | ✓ |
| Can read DVD | ✗ | ✓ | ✓ |
| Can read Blu-Ray disc | ✗ | ✗ | ✓ |
References:
- Gibson, M. (2023) Difference between CD, DVD, and Blu-ray discs, Know Computing. Available at: https://www.knowcomputing.com/difference-between-cd-dvd-and-blu-ray-discs/ (Accessed: 11 September 2023).