Computer Revision2[Data Storage]

It is used to store data and instructions for later use

1. Primary storage

2. Secondary storage

3. Offline storage

1. Directly accessible by CPU

2. Is internal to computer

3. Has faster access speed

4. Has both volatile and non-volatile memory (RAM, ROM)

5. Stores back-up instructions (ROM) and hold data currently in use (RAM)

1. ROM is non-volatile whereas RAM is volatile

2. ROM is read only whereas RAM can be read and changed

3. ROM has a smaller storage capacity than RAM

4. ROM holds boot up instructions whereas RAM holds files currently in use

• It stores boot up instructions

1. Stores data files currently in use

2. Stores application program currently in use

3. Stores part of operating system currently in use

1. Non-volatile storage

2. Not directly accessible by CPU

3. It can be internal or external to the computer (External / Internal HDD/SSD)

1. Non-volatile storage

2. Storage that is removable from a computer / portable / not internal

3. Must be connected to computer to obtain stored data

4. Used to store files as backup

5. It is not directly accessed by the CPU

6. CD / DVD / Blu-ray / USB stick / SD card / Pendrive / Flash memory

1. Hard Disk Drive

2. Magnetic tape

3. Floppy disk

1. It uses platters

2. The platters are divided into concentric tracks and sectors

3. Data is read and written using electromagnets

4. Data (0s and 1s) are represented by magnetic spots on disk

5. The disk spins at high speed

6. Has moving parts

7. Non-volatile

1. CD

2. DVD

3. Blu-ray disc

1. It uses lasers to create and read pits and lands

2. Pits and lands represent binary values

1. Solid state drive

2. Pendrive

3. Memory card

1. It uses NAND or NOR technology

2. Transistors are used as control and floating gates

3. Memory cells store voltages which represent either a 0 or 1

1. Has moving parts

2. Non-volatile storage

3. Magnetic medium

4. Data (0s and 1s) are represented by magnetising spots on disk

5. The disk is made of platters

6. The platters are mounted on a central spindle

7. The disk is divided into concentric tracks and sectors

8. The disk spins at high speed

1. Has no moving parts

2. Uses NAND / NOR technology

3. Uses flash memory to store data

4. Non-volatile storage

5. Secondary storage

6. Can be used as external storage device to back up data

7. Has a limited number of read / writes cycles

8. Uses a grid of columns and rows that has 2 transistors at each intersection

9. One transistor is called a floating gate and the second transistor is called the control gate

10. Memory cells store voltages which can represent either 0 or 1

• Stores the instructions / programs

1. Has no moving parts, so more reliable / durable in portable computer / laptop

2. Lighter so more suitable for a portable computer

3. Runs quicker

4. Runs cooler

5. Less power consumption

6. Data access is faster

7. Occupies less physical space

1. HDD has greater longevity for read / write functions // more read / write cycles which is likely to be a lot for each day

2. HDD is cheaper for larger amounts of storage device

3. HDD is a trusted technology // Expensive to change the technology

4. No requirement for the increased speed of SSD

5. No requirement for portability as a server, it does not need to be moved

1. CD

2. DVD

3. Blu-ray

1. CD-ROM :- data can be written to it only once

2. CD-R (recordable) :- data can be written to it only once

3. CD-RW (rewritable) :- data can be written to it many times

1. Red laser is used which shines onto the surface of the disk

2. It is rotated at a constant speed to be read

3. Data is represented on the surface using pits and lands

4. Pits and lands represent binary values

5. Pits reflect light back differently

6. Surface is covered in a track that spirals from the centre

1. Optical storage

2. Read using a red laser

3. Has smallest storage capacity

4. Stores data in spiral track

5. Single layer

1. Optical storage

2. Can be dual layer

3. Read using a red laser

4. Stores data in a spiral track

1. Optical storage

2. Has the largest storage capacity

3. Can be dual layer

4. Read using blue laser

5. Stores data in a spiral track

1. Uses several concentric tracks therefore has direct access

2. Allows simultaneous read/write operations as it has a read/write head

1. DVD-RW uses a single spiral track whereas DVD-RAM uses several concentric tracks

2. DVD-RW disk rotates at different speeds whereas DVD-RAM disk rotates at a constant speed

3. DVD-RW cannot be read and write at the same time whereas DVD-RAM allows simultaneous read/write operations

4. DVD-RW requires special packet reading/writing software whereas DVD-RAM requires no special read/write software

1. Virtual memory is used when RAM is full

2. Part of the secondary storage is used as RAM/ Virtual memory

3. Data from RAM is moved to the secondary storage to make space in RAM

4. When data in Virtual memory is needed, it is moved back to RAM

5. Pages of data are transferred between RAM and Virtual memory when needed

1. Allows saving data and files in an off-site location that can be accessed through internet

2. Physical servers and storage are needed to store data in cloud storage

3. Users can remotely upload their content, store them and retrieve the data as and when required

4. Cloud storage can be accessed remotely in comparison to storing data locally

1. The cloud has greater storage capacity

2. The data could be sent directly to/from cloud to any computer

3. Storage capacity can be increased without adding additional physical devices

4. There is an automatic backup of data

1. Users must have an internet connection to access data

2. Users must have a reliable internet connection to store data

3. More security issues or multiple copies of the data are stored