1.2 Memory and Storage

Question 1

Primary storage

Answer 1

Comprised of RAM and ROM. It holds data, programs and instructions that are currently in use.

Question 2

Need for primary storage

Answer 2

The CPU can access data and instructions more quickly and easily than from secondary storage devices.

Question 3

RAM

Answer 3

Random-access memory. Temporary storage of currently executing instructions and data - e.g. applications and the operating system.
-Volatile
-Read and write
-large compared to ROM

Question 4

ROM

Answer 4

Read-only Memory. Stores startup instructions known as the bootstrap.
-Non-volatile
-Read only
-Small compared to RAM

Question 5

Virtual memory

Answer 5

Using part of the hard disk as if it were random-access memory. Allows more applications to be open than physical memory can hold.
-Programs are transferred out to virtual memory from RAM when not being executed to free up space in primary storage
-transferred back when needed

Question 6

Secondary storage

Answer 6

Permanent storage of instructions and data not currently in use by the processor. Stores the operating system, applications and data. Read-and-write and non-volatile.

Question 7

Need for secondary storage

Answer 7

-ROM is read-only and RAM is volatile
-It is the storage of programs and data when the power is turned off
-and is semi-permanent storage that can change

Question 8

Common types of storage

Answer 8

-Optical (DVDs, CDs)
-Magnetic (Hard disk)
-Solid state (USB)

Question 9

Advantages of optical storage

Answer 9

-Thin
-Lightweight
-Portable

Question 10

Disadvantages of optical storage

Answer 10

-Low capacity compared to others
-slow to access
-loses data when scratched

Question 11

Advantages of magnetic storage

Answer 11

-Quick access data
-high storage capacity

Question 12

Disadvantages of magnetic storage

Answer 12

-Has moving parts, and will eventually fail
-slower access than solid state

Question 13

Disdvantages of solid state storage

Answer 13

-Medium storage capacity
-limited number of read-write cycles
-expensive

Question 14

Advantages of solid state storage

Answer 14

-small, lightweight
-fast access time
-no noise - no moving parts
-low power

Question 15

Units of data storage

Answer 15

-Bit (1)
-Nibble (4 bits)
-Byte (8 bits)
-Kilobyte (1000 bytes)
-Megabyte (1000 KB)
-Gigabyte (1000 MB)
-Terabyte (1000 GB)
-Petabyte (1000 TB)

Question 16

Binary numbers

Answer 16

A numbering scheme with only two possible values for each digit, 0 and 1.
Base 2

Question 17

8 bit binary

Answer 17

2^8 = 256 combinations
-numbers 0-255

Question 18

Denary numbers

Answer 18

A numerical system of notation that uses 10 as its base. The ten decimal base digits are 0-9.

Question 19

Hexadecimal

Answer 19

A numerical system that uses 16 as its base. The 16 hex base digits are 0-9 and A-F. Computers don’t use it but used to represent large binary numbers into a smaller number of digits for humans.

Question 20

Binary addition

Answer 20

128,64,32,16,8,4,2
Rules:
-0+0=0
-0+1=1
-1+1=1 carry 1
-1+1+1 = 1 carry 1
Practice binary addition

Question 21

Binary overflow

Answer 21

The generation of a number that is too large to be represented by the device intended to store it.

Question 22

Convert between denary and 2 digit hexadecimals

Answer 22

Practice converting

Question 23

Binary shifts

Answer 23

Shift left - times by 2
Shift right - divided by 2

Question 24

Character sets

Answer 24

Defined list of characters recognized by the computer hardware and software, with each character being represented by a single number.

Question 25

Types of character sets

Answer 25

-ASCII 7-bit character set - 2^7 = 128 combinations
-Extended ASCII 8-bit character set - 2^8 = 256 combinations
-Unicode 24-bit character set - 2^24 = 16 million combinations

Question 26

How images are stored

Answer 26

Bitmap - image made up of pixels, each square has a binary value - photographs
Vector - mathematics to store the square are stored - technical, drawings, logos, clipart

Question 27

Metadata

Answer 27

A collection of data that describes and provides information about other data.
-Such as width, height, colour depth, colour palette

Question 28

Colour/ bit depth

Answer 28

Number of bits needed to store each pixel.
Photos are usually stored in 24 bit colour depth = 2^24 = > 16 million colours

Question 29

Equation for the size of image file

Answer 29

Image height * image width * colour depth

Question 30

Converting music to digital

Answer 30

Height of the analogue signal is measured/ sampled at regular intervals and stored as binary as a digital signal

Question 31

Sample rate

Answer 31

How often (frequency) you record the amplitude of a sound wave.
The more often a sample is recorded, the smoother the playback will sound.
Measured in hertz (Hz) - E.g. 44,000 Hz = 44,000 samples taken /second

Question 32

Sound - Bit depth

Answer 32

How many gradations of amplitude can be represented in a digital wave form

Question 33

Calculating sound file size

Answer 33

Sample rate * duration (s) * bit depth

Question 34

Use of compression

Answer 34

-Reduces the size of a file so it takes up less space
-maximizes the amount you can store on a device
-smaller files are quicker when transferred over the internet
-lossy and lossless

Question 35

Lossy compression

Answer 35

A compression method where the data in a file is removed and not restored to its original form after decompression
-Used for image, music, video files
-more effective than lossless

Question 36

Lossless compression

Answer 36

Reduces file size with no loss of data
-all original data can be recovered when the file is uncompressed
-usually used for texts and spreadsheet files