1.2 Memory and Storage pt. 1

Primary storage

• Memory areas that the CPU can access quickly e.g RAM, ROM, cache - main memory

• Volatile - needs power to keep data

• Data is copied from secondary storage to main memory when needed as accessing from secondary storage is too slow

RAM

• Random Access Memory

• Where all data, files and programs are kept when in use

• Can be read from and written to

• Volatile

• When booting up, the OS is copied from secondary storage to RAM as well as any software applications, documents and files until they are closed.

• CPU able to access RAM directly

ROM

• Read Only Memory

• Non-volatile

• Can only be read from and not written to

• Comes as a small, factory-made chip on the motherboard

• Contains all the instructions that the computer needs to properly boot up - called the BIOS

• As soon as the computer is turned on, the CPU reads the instructions from ROM which tells the computer to perform self-checks and set up the computer

BIOS

• Basic Input Output System

• Loads the operating system into RAM

• Performs self-diagnostic checks on the hardware

• Provides a basic user interface where some settings can be accessed

Benefits of increasing RAM

• More RAM can temporarily store more data in faster memory

• Allows more programs to be open at once without affecting performance

• Speeds up the access of data

• Avoids the use of virtual memory which would slow performance as VM is slower to access

Virtual Memory

• Computers have a limited amount of RAM, as applications open, RAM fills with data

• When RAM is full, the computer needs somewhere else to put the data. It moves unused data to virtual memory

• Needed if too many applications are open at once and/or a particularly memory-intensive application is being used

• If the CPU needs data that is stored in VM, the data is moved back to RAM but it has a very slow transfer rate.

• When VM is in use, it makes the computer slower to respond when switching between tabs or when using a memory intensive application.

Secondary Storage

• Holds all the data when the computer is turned off/not in use

• Non-volatile

• Can be used to transfer data stored between 2 computers

• Read and write speeds are slower than storage

• Data and programs are stored permanently on secondary storage devices

Magnetic drives

• Traditional internal storage for PCs and Laptops

• Made up of a stack of magnetised metal disks that spin thousands of times a second

• Data is stored magnetically in small areas on the disks circular tracks. A moveable arm can access these areas and read or write data.

• Popular for backing up large amounts of data

• Generally long-lasting and reliable but could be damaged if dropped

Advantages and disadvantages of magnetic drives

Advantages:

• Cheaper compared to other types of storage

• Vast storage capability (800GB - 16TB)

• Fast write speed

• Longer read/write life than SSDs

Disadvantages:

• Lots of mechanical parts - prone to breaking

• Not as quick as SSDs

Magnetic tapes

• Greater storage capacities than HDDs

• Low cost per GB

• Used for backing up large amounts of data

• Slow at finding specific pieces of data - tape has to be wound to the correct place

Optical Discs

• Pits and lands are burnt into a spiral track circulating from the centre outwards. A laser beam is passed over thee pits and lands and the change in surface can be translated into 1s and 0s

• Examples include CDs, DVDs and Blu-ray

• Used for storing songs, videos and other multi-media storage, backup and archiving of data

Optical Discs

• Pits and lands are burnt into a spiral track circulating from the centre outwards. A laser beam is passed over thee pits and lands and the change in surface can be translated into 1s and 0s

• Examples include CDs, DVDs and Blu-ray

• Used for storing songs, videos and other multi-media storage, backup and archiving of data

Solid State Drives

• Uses a type of non-volatile flash memory to store data

• A large electric current is used to force electrons through a barrier and trap them on the other side. They remain there until ‘flashed’ by a new current

• Used for portable computers/devices and transporting data

Advantages and disadvantages of solid state drives

Advantages:

• Highly durable

• No moving parts

• Very fast read/write speeds

• Quicker to boot up/load programs and save/load files

• No noise

Disadvantages:

• Expensive compared to other storage devices at present

• Less storage capacity compared to other storage devices (100GB - 10TB)

• Can only be written a certain number of times before deteriorating

HDDs vs. SSDs

Advantages of HDDs:

• Cheaper

• Higher capacity

• Longer read/write life

Advantages of SSDs:

• Faster

• Don’t need defragmenting

• More shock-proof than HDDs

• Makes no noise

Capacity

The amount of data that can be stored on the device

Speed

The rate at which the device can transfer data

Portability

If we can easily move around the device or not

Durability

The length of time the device will safely store data without failing

Reliability

Whether the data iis stored without any technical errors and the data is still reliable

Cost

The price of the device