MEMORY AND STORAGE

What are the two main types of primary storage?

• RAM (Random Access Memory)

• ROM (Read-Only Memory).

What happens to the data in RAM when the power is turned off?

it is lost (RAM is volatile).

Can data be written to ROM during normal operation?

No, ROM is read-only

What type of data does RAM typically hold?

The operating system, running applications, and associated data while the computer is in use.

Why is ROM important during the boot process?

It stores the bootstrap loader/BIOS to start the computer.

Is RAM considered permanent or temporary storage?

Temporary, as it only works while the computer is powered on.

What is a key difference between RAM and ROM in terms of volatility?

RAM is volatile (loses data when powered off), while ROM is non-volatile (retains data even when powered off)

What happens if there is insufficient RAM to run multiple applications?

The computer uses virtual memory by temporarily moving data to/from secondary storage.

What is virtual memory?

a portion of secondary storage used as an extension of RAM to handle more data than available physical RAM.

How is ROM data retained when the computer is turned off?

ROM is non-volatile, so it retains data permanently.

Why is secondary storage needed in a computer?

To store files and programs permanently; it is non-volatile, reliable, low cost, and high capacity.

What type of storage does magnetic storage typically use?

Hard Disk Drives (HDDs).

How do magnetic storage devices read and write data?

a moving read/write head moves across rotating magnetic platters.

What are the advantages of magnetic storage? (3)

• Reliable

• cost-effective

• provides high-capacity storage.

What is a disadvantage of magnetic storage?

Not very portable due to moving parts.

What type of memory do solid-state drives (SSDs) use?

Flash memory.

Why is data access faster in SSDs compared to HDDs?

SSDs have no moving parts.

What are some advantages of SSDs over HDDs?

• Low power requirements

• no noise or heat

• lightweight

• compact

• robust

What is a disadvantage of SSDs compared to HDDs?

Smaller capacity and higher cost per unit of storage.

In what types of devices are SSDs commonly used?

Tablet computers and mobile phones.

What is the principle behind optical storage devices?

They use the properties of light to store data.

What are examples of optical storage media?

CDs, DVDs, and Blu-ray disks.

How does an optical storage device read data?

By reflecting laser light on the disk’s surface and interpreting reflections as 1s or 0s

What is a major disadvantage of optical storage?

It is easily damaged by mishandling and scratches.

How many bits make up a nibble?

4 bits.

How many bits make up a byte?

8 bits.

What is the equivalent of 1000 bytes?

1 kilobyte (KB).

How many kilobytes (KB) are in a megabyte (MB)?

1000 KB.

How many megabytes (MB) are in a gigabyte (GB)?

1000 MB.

How many gigabytes (GB) are in a terabyte (TB)?

1000 GB.

How many terabytes (TB) are in a petabyte (PB)?

1000 TB.

What formula is used to calculate the file size of a sound file?

Sample rate (Hz) × Duration (s) × Bit depth.

How is the file size of an image calculated?

Colour depth × Image height (pixels) × Image width (pixels).

What formula is used to calculate the file size of a text file?

Bits per character × Number of characters

What is the range of denary numbers

0-255

What is the range of hexadecimal numbers?

00-FF

What is the range of binary numbers in 8 bits?

00000000 - 11111111.

What does a left shift operation in binary represent

Multiplying by 2.

What does a right shift operation in binary represent?

Dividing by 2.

What is an overflow error in binary addition?

It occurs when there is a carry bit or leftover bit that exceeds the storage capacity.

What is the most significant bit (MSB) in an 8-bit number?

The leftmost digit, which represents 128 in decimal.

10000000

What is the least significant bit (LSB) in an 8-bit number?

The rightmost digit, which represents 1 in decimal.

00000001

How is each character represented in a computer

By a numeric binary code

What is the character set of a computer?

A list of all the characters available to the computer

What is ASCII, and how many characters can it represent?

ASCII is a 7-bit code that represents 128 characters

What is extended ASCII, and how many characters can it represent?

Extended ASCII uses an 8th bit, allowing it to represent 256 characters, including extra symbols and non-English characters.

What is Unicode, and how many characters can it represent in its original form?

Unicode originally used a 16-bit code to represent 65,536 characters

How does Unicode differ from ASCII?

Unicode has been extended to use more bits to represent billions of characters, while original ASCII and extended ASCII codes are subsets of Unicode.

What is the purpose of Unicode?

To represent a wide range of characters and symbols from various languages and systems

How are images represented on a computer screen?

As a series of pixels stored as binary codes.

What determines how many colors a pixel can represent

The number of bits used for each pixel.

How many colors can be represented with 1 bit per pixel?

2 colors (0 or 1).

How many colors can be represented with 2 bits per pixel?

4 colors (2²).

How many colors can be represented with 8 bits per pixel?

256 colors (2⁸).

What is color depth in an image?

The number of bits used per pixel.

What does resolution refer to in an image?

The number of dots (pixels) per unit of distance, e.g., DPI (dots per inch).

What is the impact of higher color depth on an image?

It allows more colors to be represented, improving quality, but increases file size

What is the effect of higher resolution on an image?

It improves quality and allows enlargement without losing detail but increases file size.

What kind of information is stored in image metadata?

• Color depth

• resolution

• geographical data

• date created/modified

• file size.

What type of data are sounds initially, and why?

Analogue, because they are a series of continuously varying vibrations

How is analogue sound converted for storage on a computer?

It is sampled at regular intervals and converted into binary.

What is sample rate?

The number of samples taken per second, measured in Hz.

What does 1 Hz represent in sound sampling?

One sample per second.

What is bit depth in sound storage?

The number of bits used to store each sample.

What factors determine the size of a sound file?

• Sample rate

• duration

• bit depth.

What is lossy compression?

A method that removes data to reduce file size. The original file cannot be fully restored.

What is lossless compression?

A form of compression that encodes digital files without losing detail.

Why is lossy compression used for images/videos?

Reduces size without noticeable quality loss.

Can you restore a lossy compressed file?

No, some data is lost permanently.

How does lossless compression work?

Finds patterns and stores data efficiently, preserving the original.

Which files need lossless compression?

Text and audio, where exact data is needed.

Main difference between lossy and lossless?

Lossy removes data, lossless keeps all data intact.

Why is compression needed?

To reduce file sizes for faster transfers, saving space on devices with limited storage, and making data more efficient to handle

What are the trade-offs in compression?

Compression reduces file sizes but may affect quality, bandwidth usage, and processing power.

What are the key points of lossy compression?

Removes data, saves space, irreversible, used for sound, images, and video.

Why is lossless compression needed for some files?

Losing data can make files unreadable, like text documents or programs

What is lossless compression?

Reduces file size without losing data, allowing the original file to be exactly restored.

What are examples of lossless compression methods?

Dictionary coding and Run Length Encoding (RLE).