CS P1 - 1.1.3 - Input, Output and Storage

What does "input and output devices" mean?

devices that provide/receive data from a computer

Examples of input devices?

sensors - thermistor, gyroscope, altimeter

Examples of output devices?

speaker, monitor, actuator

Secondary storage definition?

non-volatile memory that is used to store programs and files long term

Types of secondary storage?

Optical, Magnetic and Flash

How does optical storage work + Examples?

It uses different reflections of light to read data, and uses a laser to write data. Flat parts are called lands, bumpy parts called pits. Examples are CDs, DVDs, Blurays.

Pros and cons of Optical Storage?

Pros: reliable and good portability

Cons: smaller capacity, slower to read/write, not durable, need a disc drive.

How does Magnetic storage work + Examples?

Data written by changing magnetism on the medium, and read by detecting this. e.g. HDDs, cassettes, swipe cards.

Pros and cons of magnetic storage?

Pros: large capabilities and cheap to buy, usually reliable although sometimes do fail

Cons: generally not durable, can be noisy

How does Flash storage work + Examples?

No moving parts --> uses electronic circuit to store data e.g. SSD's, usb memory sticks, memory cards

Pros and cons of Flash storage?

Pros: generally reliable, uses less power, can be very durable, can be portable, generally faster to read/write

Cons: higher cost per Gb, sometimes have a limited number of writes (leading to reliability problems long term)

What is primary storage?

Memory that is directly connected to the CPU, e.g. ROM and RAM. It is needed so different programs can be run by the CPU.

What is RAM and describe its features?

Random Access Memory - it holds data and programs that are currently in use. When a program is opened, it is copied from secondary storage into RAM. This is volatile. You can access items from any part of the memory at the same speed.

What is ROM and describe its features?

Read Only Memory - it cant be easily changed by the user, it is non-volatile, contains BIOS - the first program which runs when the computer is turned on.

What is BIOS?

Basic Input Output System:

- Begins with a POST (Power On Self Test), this tests if the components are working and then the user is alerted to faults.

- Allows the user to configure their hardware e.g. change where to boot up from, overclock the CPU

- Will then boot up the OS; it will copy part of the OS from 2ndary storage into RAM, then the OS continues the booting process

What is virtual storage + examples?

Appears like the files exist in one place, but the files are physically held elsewhere. e.g. cloud storage, NAS, redundant array of independent disks

What is cloud storage, and its pros vs cons?

When files are held in an off-site location and are accessed through the internet.

Pros: easily scalable, easy for collaboration, often implement policies like automatic backup and encryption, can be accessed from any location + any device.

Cons: need internet connection to access, ongoing cost, reliance on the cloud provider.

What is NAS, and its pros vs cons?

Network-attached storage: when files are held on a dedicated file server and are accessed through your local network.

Pros: more control than cloud storage, more scalable than single device

Cons: high initial cost, expertise needed to run

What is redundant array of independent disks, and its pros vs cons?

When files are split and copied accross multiple storage units.

Pros: high performance (parallel access), built-in back ups

Cons: high initial cost, expertise needed to run

What are embedded systems and describe them?

A computer that can only perform a limited range of functions that is surrounded by a larger system. They need a computer to respond to inputs, make decisions and do tasks automatically.

They are smaller, cheaper and specialised. They tend to have: memory and CPU on same component, more ROM than RAM, use ROM as secondary storage, work in real time.

e.g. thermostat, microwave, robotic hoovers, washing machines.