Unit 1.3 Flashcards
What is secondary storage?
Long term storage of files, software and the OS
Why is secondary storage needed?
RAM is a temporary memory storage and it is volatile, so we need a non-volatile, high capacity storage system.
What is the conventional secondary storage device in computers?
The HDD
- has a large storage capacity (in the TB range)
- but it does take longer to access data from here than from RAM – so we move the data to RAM when we are actually using it.
What are the three types of storage technologies?
Optical storage
Magnetic storage
Solid state storage
What is optical storage?
uses laser light to burn pits onto the surface to represent 0/1
What are examples of optical storage?
CD/DVD storage
What is magnetic storage?
HDD has an arm that moves across a spinning disk that picks up different levels of magnetism (0/1) – a tape head reads the magnetic state as the passes through it.
What are examples of magnetic storage?
HDD or magnetic tape
What is solid state storage?
made from transistors (switches) which can have states of on or off (0/1)
What are examples of solid state storage?
Flash memory/USB sticks/SD cards
What are the characteristics of storage technologies?
Capacity - how much data can it store?
Speed - how fast can it access the data?
Portability - how easy is it to move it from one place to another
Durability - how well does it last e.g. if it is dropped
Reliability - how consistently does it perform?
Cost - how much does it cost per KB, MB or GB?
What are the units of data in computing starting from small to big?
bit, byte, KB, MB, GB, TB, PB
What is the data capacity calculation for text files?
1 byte per character, + 10% for any overheads (e.g. file type);
How much storage does text require?
1 byte per character
How much storage does an integer require?
Integer
4/8 bytes
