Memory and storge part 1

Question 1

Why is primary storage needed in Von Neumann Architecture?

Answer 1

In the Von Neumann Architecture, primary storage is needed to store programs that are currently running and need to be accessed by the CPU.

Question 2

What are the two types of primary storage used?

Answer 2

RAM (Random Access Memory) and ROM (Read Only Memory)

Question 3

What is RAM used for?

Answer 3

RAM is used to store running programs and data when the computer is in use.

Question 4

What are the characteristics of RAM?

Answer 4

RAM is often referred to as Main Memory.
It can be read to and written from.
Access to RAM is much faster than access to a hard drive
it is volatile, so data stored in RAM is lost when the power turns off

Question 5

When your computer is turned off, where is the data stored?

Answer 5

All your programs and data are stored permanently on the hard drive - this is known as non-volatile storage so it doesn’t lose the data when power is turned off.

Question 6

What does RAM usually store?

Answer 6

Operating system (or part that is currently in use)
The software currently in use
The data which the software is using

Question 7

What is ROM used for?

Answer 7

ROM is used to store the bootstrap, which is the initial program that is run when the computer is turned on. It tells the computer where it will find the operating system on the hard drive.
ROM also stores the Basic Input/Output System (BIOS). the BIOS can run without a hard drive or secondary storage present. It controls basic technical configuration of the computer such as the processor speed or the system time.

Question 8

What are the characteristics of ROM?

Answer 8

Data is read from ROM, but cannot be written to
It is non-volatile, so data won’t be lost when the power is turned off

Question 9

What are the differences between RAM and ROM?

Answer 9

RAM:
Size - typically 4GB to 32GB
Used to store running programs and operating system
Can be read from and written to
Is volatile

ROM:
Size - typically 4MB - 8MB
Used to store BIOS and Bootstrap
Can be read from
Cannot be written to
Is not volatile

Question 10

What is virtual memory?

Answer 10

Virtual memory is a part of the hard drive used as an extension to RAM.

Question 11

Why might virtual memory be needed?

Answer 11

When RAM is (close to being) full, virtual memory can be used so that the computer remains operational.

Question 12

How does virtual memory work?

Answer 12

Programs and data that are not currently being executed can be (temporarily) transferred to virtual memory.
So the computer can remain fully operational and more space is allowed in RAM for currently running programs.
Virtual memory is an area of secondary storage (e.g. the hard drive)
Programs and data are transferred back to RAM when they are needed
It’s a temporary measure

Question 13

What are the advantages and disadvantages of virtual memory?

Answer 13

Advantages:
Uses cheap secondary storage on the hard drive
Prevents error messages saying “out of memory” - the programs and files will still open

Disadvantages:
Accessing virtual memory is very slow
To access data, the existing data in RAM needs to be copied into virtual memory, then data in virtual memory needs to be copied into RAM

Question 14

Why is secondary storage needed?

Answer 14

A computer needs secondary storage for long term storage of programs and data that are not currently in use.
Secondary storage is needed as ROM is read only and RAM is volatile.
Performance of secondary storage is much slower than primary storage but its capacity is much higher.

Question 15

Is cache primary or secondary storge?

Answer 15

Primary storage

Question 16

What are the characteristics of secondary storage?

Answer 16

Capacity - what is the maximum amount of data that can be stored?
Speed - how fast can data be read from or written to? (accessed/transferred)
Cost - how much does it cost?
Portability - How easy is it to move around? What is the physical size? Weight?
Durability - How robust is the storage - is it easily damaged?
Reliability - what is the probability that the device will consistently perform its function - can it be used again and again without failing?

Question 17

What are the three common types of secondary storage?

Answer 17

Magnetic - mechanical parts move over the disk’s surface to read and write data magnetically, or a drive head reads a magnetic tape
Optical - Lasers read and write the data using light
Solid state - data is recorded onto solid memory chips without any moving parts

Question 18

What are the advantages, disadvantages, uses and size of magnetic storage?

Answer 18

Advantages:
Cheap, large storage capacities, relatively fast write speed
Disadvantages:0
Lots of mechanical parts, not very durable, sealed unit due to disk head and platter precision, not very portable
Uses:
Personal computers, storage and large quantities of data
Size:
500GB - 12TB or greater

Question 19

What are the advantages, disadvantages, uses and size of optical storage?

Answer 19

Advantages:
Cheap, easily portable, takes up little physical space
Disadvantages:
less storage capacity compared to other types
easily damaged/scratched, requires a CD reader
slow write speeds
Uses:
songs, videos or other multi-media storage, backup and archiving of data
Capacity:
CD-ROM - up to 720MB
DVD - 8.4 GB
Blu-ray - up to 50GB

Question 20

What are the advantages, disadvantages, uses and size of solid state drives?

Answer 20

Advantages:
Highly durable, no moving parts, very fast read/write speeds,
no noisy fan or drive arm, faster start up times
Disadvantages:
More expensive than magnetic hard disks, similar storage
capacity as magnetic disks
Uses:
Higher end computers
Laptops
Smartphones and tablets
Capacity:
100GB - 16TB

Question 21

What’s good about flash memory?

Answer 21

Low cost, portable, no moving parts, durable
This makes them ideal for a range of offline devices:
Cameras
Mobile phones
USB memory sticks