1.2 Memory and storage

What is RAM?

Random Access Memory that stores data and instructions currently in use

What type of memory is RAM?

Volatile memory

What happens to RAM when power is turned off?

Its contents are lost

What is ROM?

Read-Only Memory that stores firmware

What type of memory is ROM?

Non-volatile memory

What is stored in ROM?

Firmware needed to boot the computer

Can ROM be modified?

No, it is read-only during normal use

What is virtual memory?

Part of secondary storage used as extra RAM when RAM is full

Why is virtual memory slower than RAM?

Because it uses secondary storage like a hard drive

Why is primary storage needed?

To provide fast access to data currently used by the CPU

What does primary storage consist of?

RAM and ROM

What is secondary storage?

Non-volatile storage not directly accessed by the CPU

Why is secondary storage needed?

To store data long-term when power is off

What are the three types of secondary storage?

Solid-state, optical, magnetic

What is solid-state storage?

Storage using electrical circuits with no moving parts

Give examples of solid-state storage

SSDs and flash drives

Advantages of solid-state storage

Very fast, durable, no moving parts

Disadvantages of solid-state storage

Expensive per GB

What is optical storage?

Storage that uses lasers to read/write data

Give examples of optical storage

CDs, DVDs, Blu-rays

Advantages of optical storage

Cheap per disk, good for media distribution

Disadvantages of optical storage

Low capacity, easily damaged

What is magnetic storage?

Storage using magnetised regions on disks

Example of magnetic storage

Hard disk drive (HDD)

Advantages of magnetic storage

High capacity, cheap per GB

Disadvantages of magnetic storage

Slow, fragile, moving parts

What is a bit?

A single binary digit (0 or 1)

What is a nibble?

4 bits

What is a byte?

8 bits

How many bytes in a kilobyte (OCR)?

1000 bytes

How many kilobytes in a megabyte?

1000 KB

How many megabytes in a gigabyte?

1000 MB

Why do computers use binary?

Because hardware only has two states (on/off)

What is binary?

Base 2 number system using 0 and 1

What is decimal?

Base 10 number system using digits 0–9

What is the most significant bit?

The leftmost bit with highest value

What is the least significant bit?

The rightmost bit with lowest value

Does adding leading zeros change a binary number?

No

What is hexadecimal?

Base 16 number system using 0–9 and A–F

Why is hexadecimal used?

It is more compact and easier to read than binary

How many bits does one hex digit represent?

4 bits

What is a binary shift?

Moving bits left or right

What does a left shift do?

Multiplies by 2 per shift

What does a right shift do?

Divides by 2 per shift

What is character encoding?

Converting characters into binary

What is a character set?

A set of characters with corresponding binary codes

What is ASCII?

A character set using 8 bits per character

What is Unicode?

A character set using 8–32 bits allowing more characters

Why is Unicode used?

To represent more languages and symbols

What is the formula for text file size?

Bits per character × number of characters

What is a pixel?

A single point in an image

What is resolution?

Number of pixels (width × height)

What is colour depth?

Number of bits per pixel

How does increasing resolution affect file size?

Increases file size and quality

How does increasing colour depth affect file size?

Increases file size and quality

What is the image file size formula?

Colour depth × width × height

What is sampling in sound?

Taking measurements of a sound wave

What is sampling rate?

Number of samples per second (Hz)

What is bit depth (sound)?

Bits used per sample

How does sampling rate affect sound quality?

Higher rate increases quality and file size

How does bit depth affect sound quality?

Higher depth increases quality and file size

What is the sound file size formula?

Sample rate × duration × bit depth

How do you convert bits to bytes?

Divide by 8

What is data compression?

Reducing file size

Why compress data?

Save space and speed up transfer

What is lossless compression?

Compression with no loss of data

Advantages of lossless compression

No quality loss

Disadvantages of lossless compression

Less reduction in size

What is lossy compression?

Compression where some data is lost

Advantages of lossy compression

Smaller file sizes

Disadvantages of lossy compression

Loss of quality and irreversible