Comp Sci 1.2 Memory and Storage

What is the primary function of RAM (Random Access Memory) in a computer system?

It stores the operating system, programs, and data that are currently in use.

How is 'volatility' defined in the context of computer memory?

Data is lost when the power to the device is turned off.

Why is ROM (Read Only Memory) classified as non-volatile?

It retains its data even when the power is turned off.

What is the specific purpose of the BIOS or Bootstrap loader stored in ROM?

It contains the start-up instructions required to boot the computer.

Which type of primary storage allows both reading and writing of data?

RAM (Random Access Memory).

In terms of typical capacity, how does ROM compare to RAM?

ROM is much smaller (e.g. 1MB - 2MB) compared to RAM (e.g. 8GB - 32GB).

What occurs when the RAM is full and the computer needs to process more data?

The computer uses a section of secondary storage as 'Virtual Memory'.

What is the process of moving data between RAM and the paging file on secondary storage called?

Swapping.

What is the primary drawback of using Virtual Memory?

It makes the computer slower because secondary storage is much slower at data transfer than RAM.

Which term describes the performance issue caused by excessive swapping between RAM and secondary storage?

Disk thrashing.

What is the function of Cache memory within the CPU?

It stores frequently used instructions to reduce the time the CPU spends waiting for data from RAM.

Why do computer systems require secondary storage?

To keep files and programs stored long-term in a non-volatile format.

Identify the three common types of secondary storage media.

Magnetic, Solid State, and Optical.

Which secondary storage type is known for having a very high capacity at a very low cost?

Magnetic storage.

Why is Solid State storage generally more durable than Magnetic storage?

It has no moving parts that can be damaged if the device is dropped or moved.

Which secondary storage type is most suitable for distributing small amounts of data due to its high portability and low cost?

Optical storage.

How does the speed of a Solid State Drive (SSD) compare to a Magnetic Hard Disk Drive (HDD)?

Solid State storage is significantly faster.

What is the typical capacity level of Optical storage media like CDs or DVDs?

Low capacity.

Why is the reliability of Magnetic storage considered high despite its low durability?

It is designed to last a long time if kept stationary in a stable environment.

What is the smallest unit of data a computer can process?

A bit (a single 0 or 1).

How many bits make up a single 'nibble'?

4 bits.

How many bits are contained in one byte?

8 bits.

In OCR GCSE calculations, how many bytes are typically in one Kilobyte (KB)?

1,000 bytes (though 1,024 is also accepted).

How many Megabytes (MB) constitute one Gigabyte (GB)?

1,000 MB.

Which unit of storage is larger than a Gigabyte but smaller than a Petabyte?

Terabyte (TB).

Why must all data be converted into binary format to be processed by a computer?

Computers use transistors which only have two states: On (1) and Off (0).

What is the result of the binary addition $1 + 1$?

0 with a carry of 1 (representing 2 in denary).

What is the result of the binary addition $1 + 1 + 1$?

1 with a carry of 1 (representing 3 in denary).

When does an 'overflow error' occur during binary addition?

When the result requires more bits than the CPU has available (e.g. a 9th bit in an 8-bit system).

What is the mathematical effect of performing a 1-place binary shift to the left?

The number is multiplied by 2.

What is the mathematical effect of performing a 2-place binary shift to the right?

The number is divided by 4 (integer division).

What happens to bits that are shifted past the end of a register during a right shift?

They are lost, which can lead to a loss of precision.

Which number system uses base-16 and includes characters 0-9 and A-F?

Hexadecimal.

What is one reason why programmers prefer to use hexadecimal over binary?

It is easier for humans to read and remember than long strings of binary.

In hexadecimal, what denary value does the letter 'F' represent?

15.

Name one common use of hexadecimal in computing.

MAC addresses (or HTML colour codes / error messages).

What is the definition of a 'character set'?

A collection of all the characters and symbols that can be represented by a computer system.

How many bits were originally used by the standard ASCII character set?

7 bits (representing 128 characters), though often stored in 8 bits.

What is the primary advantage of Unicode over ASCII?

Unicode uses more bits (e.g. 16 or 32), allowing it to represent thousands of characters from all world languages.

If the character code for 'A' is 65, what is the character code for 'C'?

67 (Character sets are logically ordered).

What is a 'pixel' in the context of digital images?

A single point of colour in an image; the smallest addressable element of a picture.

How is the total number of pixels in an image (resolution) calculated?

Width $\times$ Height.

What does 'colour depth' represent in image storage?

The number of bits used to represent the colour of each pixel.

How does increasing the resolution of an image affect its file size?

It increases the file size because there are more pixels to store.

What is 'metadata'?

Additional data stored within a file that provides information about the file (e.g. GPS location, date created, file format).

What is the formula for calculating the file size of a digital image?

Colour depth $\times$ Image height (px) $\times$ Image width (px).

In digital sound, what does 'sample rate' mean?

The number of samples of the audio wave taken per second, measured in Hertz (Hz).

What is the 'bit depth' of a sound file?

The number of bits available to store each individual sound sample.

How does increasing the sample rate affect the quality of a sound recording?

It improves the playback quality as the digital wave more closely matches the original analogue wave.

What is the formula for calculating the file size of a sound recording?

Sample Rate $\times$ Bit Depth $\times$ Duration (seconds).

What is the main goal of file compression?

To reduce the file size so that the file takes up less storage space or is faster to transmit.

How does 'Lossy' compression work?

It permanently removes data that the human eye or ear is unlikely to perceive.

What is the primary benefit of 'Lossless' compression compared to 'Lossy'?

No data is lost, and the original file can be perfectly reconstructed.

Give an example of a file format that uses Lossy compression.

JPEG (for images) or MP3 (for sound).

Why is Lossless compression required for text documents or executable programs?

Losing even a small amount of data would make the text unreadable or the program crash.

What is 'Run Length Encoding' (RLE)?

A form of lossless compression that stores data as a value and a count of how many times that value repeats.

Why is it generally unnecessary to defragment a Solid State Drive (SSD)?

SSDs have no moving parts and can access any sector instantly; defragmenting them can also shorten their lifespan.

What is the physical cause of 'fragmentation' on a Magnetic Hard Drive?

Files are stored in non-contiguous (separated) blocks across the spinning platters.

How does defragmentation software improve system performance for Magnetic drives?

It reorganises files into contiguous sectors so the read/write head has to move less.

How many bits are needed to represent 16 different colours in an image?

4 bits (since $2^{4} = 16$).

Convert the denary number 10 into 4-bit binary.

1010.

Convert the hexadecimal number '1A' into denary.

26 ($1 \times 16 + 10$).

What is the result of a left binary shift of 3 places on the binary number 00000010 (denary 2)?

00010000 (denary 16).

Which data unit is equal to 1,000 Terabytes?

1 Petabyte (PB).

How does increasing the bit depth of a sound file affect its size?

It increases the file size because more bits are stored for every sample.

True or False: Metadata is counted as part of the total file size in a calculation.

True (OCR allows for metadata in calculations).

If an image has a resolution of $100 \times 100$ and a colour depth of 8 bits, what is its size in bytes?

10,000 bytes ($100 \times 100 \times 8$ bits = 80,000 bits; 80,000 / 8 = 10,000 bytes).

What unit is used to measure the clock speed of a CPU?

Hertz (Hz), usually Gigahertz (GHz).

How does increasing the number of CPU cores affect performance?

It allows multiple instructions to be processed simultaneously (parallel processing).

What is the primary function of a Device Driver?

It acts as a 'translator' between the Operating System and the hardware peripheral.

What is the difference between an IP address and a MAC address?

A MAC address is a permanent physical address, while an IP address is a logical address that can change.

Which protocol is used for sending emails between servers?

SMTP (Simple Mail Transfer Protocol).

How does IMAP differ from POP when receiving emails?

IMAP synchronises emails with the server, while POP usually deletes them from the server once downloaded.

What is the purpose of the 'Application Layer' in the TCP/IP model?

It is where network applications like web browsers or email clients operate (using HTTP, FTP, etc.).

What is the purpose of 'Encryption Software' as a utility?

It scrambles data using an algorithm so it cannot be understood without a decryption key.

Define 'Open Source' software.

Software where the source code is available for anyone to view, edit, and redistribute.

What is 'Proprietary Software'?

Software where the source code is hidden and users must pay for a license to use it.

What environmental issue is associated with the disposal of old computer hardware?

E-waste, which contains toxic chemicals like lead and mercury that can harm the environment.

What is 'social engineering' in the context of network security?

Manipulating people into giving away confidential information, such as passwords.

What is the purpose of a 'Firewall'?

To monitor incoming and outgoing network traffic and block unauthorised access based on security rules.

What is 'SQL Injection'?

A malicious attack where SQL code is entered into a website's input boxes to manipulate or steal database data.

Which register holds the address of the next instruction to be processed?

Program Counter (PC).

What does the 'Accumulator' (ACC) store?

The immediate results of calculations performed by the ALU.

What are the three stages of the CPU cycle?

Fetch, Decode, and Execute.

In binary subtraction, what is the 'Two's Complement' method used for?

To represent negative numbers in binary.

Calculate the file size in bits of a 10-second sound clip with a 44,100 Hz sample rate and 16-bit depth.

7,056,000 bits ($44,100 \times 16 \times 10$).

Which unit is used to describe a set of 8 bits?

A Byte.

What is 'lossy' sound compression typically called?

Perceptual coding (removes frequencies humans can't hear).

Why does a larger cache size improve CPU performance?

It allows the CPU to store more frequently used data closer to the processor, reducing slower RAM fetches.

What occurs during the 'Decode' stage of the Fetch-Execute cycle?

The Control Unit (CU) inspects the instruction to determine what action is required.

What is the function of the Memory Address Register (MAR)?

It holds the address of the location in memory where data is to be fetched from or stored.

What is the function of the Memory Data Register (MDR)?

It holds the actual data or instruction that has just been fetched from, or is about to be written to, memory.