3.4 Computer Systems

• How does pixel resolution and colour depth affect image quality?

  The higher the pixel resolution and colour depth, the greater the quality of the image.
• What happens to the file size of an image when pixel resolution or colour depth is reduced?

  The file size of the image will also reduce.
• How many colours can an image with 4 bits per pixel represent?

  16 colours.
• What is the role of an ADC in sound processing?

  An ADC converts analogue sound into a digital format.
• What are the two main factors that affect sound quality?

  Sampling rate and sample resolution.
• How does increasing the sampling rate affect file size?

  Increasing the sampling rate will increase the file size.
• What is the formula for calculating sound file size?

  Sound file size = sampling rate (Hz) x sample resolution (bits) x time (s).
• What is the formula for calculating image file size?

  Image file size = colour depth (bits) x width (pixels) x height (pixels).
• What are the differences between lossy and lossless compression?

  • Lossy compression reduces file size significantly but lowers quality irreversibly (e.g., JPEG, MP3).
  • Lossless compression reduces file size minimally but retains original quality (e.g., PNG, GIF).
• What is Huffman Encoding used for?

  Huffman Encoding is used for lossless data compression by encoding characters based on their frequency.
• What is the purpose of secondary storage?

  Secondary storage is needed to save data and programs that are needed after the computer is turned off. It is a form of non-volatile memory.
• How does secondary storage differ from main memory (RAM)?

  Secondary storage can hold much greater capacity of memory than main memory, but is slower to access as it is not directly accessible by the CPU.
• What are the main factors to consider when choosing a secondary storage device?

  Capacity, speed, portability, durability, reliability, and cost.
• How does data storage work in a hard disk drive (HDD)?

  Data is stored using magnetic dots which have a positive or negative polarity, on areas of the disk called sectors which are found within circular tracks. The disk spins at a fast rate to ensure all the data is read.
• What are the main advantages of magnetic storage like HDDs?

  Largest storage capacity compared to other secondary storage devices.
• What is the purpose of the operating system (OS)?

  The operating system allows the hardware and software to communicate with each other and run other software (programs).
• What are the main functions of an operating system?

  The OS is responsible for management of memory/multitasking, input/output devices, security, processors, and applications.
• What are the two main types of computer systems?

  Non-embedded systems (e.g. laptops, smartphones) and embedded systems (e.g. washing machine, SAT NAV).
• How do embedded systems differ from non-embedded systems?

  Embedded systems are dedicated systems produced to be efficient at carrying out specific tasks, contain more ROM than RAM, and do not use secondary storage.
• What are the 5 main components of a CPU?

  Control Unit (CU), Arithmetic & Logic Unit (ALU), Clock, Registers, and Buses (data, address, control).
• What is the purpose of the CPU FDE (Fetch, Decode, Execute) cycle?

  The CPU continuously reads instructions stored in main memory and executes them as required: Fetch the next instruction, Decode the instruction, and Execute the instruction.

  
• What are the main factors that affect CPU performance?

  Clock speed, number of cores, and cache size.
• How would you compare the performance of two CPUs with different clock speeds and core counts?

  To compare CPU performance, you need to consider both the clock speed and the number of cores. For example, a dual core CPU with 3.2GHz could be considered better than a quad core CPU with 2.1GHz if you only compare the speeds, but the quad core would be better overall as it can process more instructions per second in total.
• What is the difference between RAM and ROM?

  RAM (Random Access Memory) is used to store running applications while the computer is on, while ROM (Read Only Memory) is used to store the BIOS instructions needed to turn the computer on.
• What are the key differences between magnetic, optical, and solid-state secondary storage devices?

  • Magnetic (HDDs): Largest storage capacity, slower access speeds, more susceptible to physical damage
  • Optical (CDs, DVDs, Blu-rays): Moderate capacity, moderate access speeds, less susceptible to physical damage
  • Solid-state (SSDs, USB drives): Smaller capacity, faster access speeds, more resistant to physical damage
• How do the characteristics of secondary storage devices impact their suitability for different use cases?

  The choice of secondary storage device depends on the required capacity, speed, portability, durability, reliability, and cost. For example, HDDs provide large capacity but slower speeds, making them suitable for general file storage, while SSDs have faster speeds but lower capacity, making them more suitable for operating system and application storage.
• What is the purpose of the BIOS (Basic Input/Output System)?

  The BIOS is stored in ROM and contains the instructions needed to turn the computer on and start the boot process.
• How do the components of the CPU (CU, ALU, Registers, Buses) work together to execute instructions?

  • Control Unit (CU): Directs the flow of instructions and coordinates the other components
  • Arithmetic Logic Unit (ALU): Performs arithmetic and logical operations on data
  • Registers: Provide high-speed temporary storage for data and addresses used in the FDE cycle
  • Buses: Allow the transfer of data, addresses, and control signals between the CPU components

  The FDE (Fetch, Decode, Execute) cycle continuously reads instructions from memory, decodes them, and executes the required operations.

  
• If you wanted to maximize the performance of a CPU, which factors would you focus on improving?

  To maximize CPU performance, you would focus on increasing the clock speed, adding more cores, and increasing the cache size.
• What is the purpose of the CPU clock?

  The clock controls the number of instructions carried out per second and is responsible for synchronizing the CPU operations.
• What are the key differences between non-embedded and embedded computer systems?

  Non-embedded systems:

  • General-purpose computers (laptops, smartphones)
  • Use an operating system to manage hardware and software
  • Have larger main memory (RAM) and secondary storage

  
  

  Embedded systems:

  • Dedicated systems built into other devices (washing machines, SAT NAVs)
  • Do not use an operating system, only have the necessary software
  • Have more ROM than RAM, and do not use secondary storage
• What is the purpose of the Arithmetic Logic Unit (ALU) in a CPU?

  The ALU is responsible for performing arithmetic and logical calculations within the processor.
• How do the functions of the control unit (CU) and arithmetic logic unit (ALU) differ within the CPU?

  The control unit directs the flow of instructions and coordinates the other CPU components, while the arithmetic logic unit is responsible for performing the actual arithmetic and logical calculations.
• What are the key differences between RAM and ROM in terms of their purpose and characteristics?

  RAM (Random Access Memory):

  • Volatile memory used to store running applications and data
  • Can be read from and written to by the CPU
  • Contents are lost when power is turned off

  
  

  ROM (Read-Only Memory):

  • Non-volatile memory used to store the BIOS instructions
  • Can only be read from, not written to by the CPU
  • Contents remain even when power is turned off
• What is the purpose of the buses in a CPU?

  The buses are a collection of wires used to send data, addresses, and control signals between the different components of the CPU.
• If you wanted to increase the performance of a CPU, which component would you focus on upgrading?

  To increase CPU performance, you would focus on upgrading the clock speed, adding more cores, and increasing the cache size.
• How do the functions of the operating system (OS) contribute to the overall performance and usability of a computer system?

  The OS contributes to computer performance and usability by:

  • Managing memory and multitasking to allow efficient use of resources
  • Controlling input/output devices and providing device drivers for connectivity
  • Implementing security features to protect the system and user data
  • Scheduling processor usage and allocating tasks to cores
  • Providing a user interface for interacting with the computer
• What is the purpose of the Fetch-Decode-Execute (FDE) cycle in a CPU?

  The FDE cycle is the process by which the CPU continuously reads instructions stored in main memory, decodes them, and executes the required operations.

  
• How do the characteristics of embedded systems differ from non-embedded systems?

  Embedded systems are dedicated devices built to efficiently perform specific tasks, contain more ROM than RAM, and do not use secondary storage, unlike general-purpose non-embedded systems like laptops and smartphones.
• What are the key factors that affect the performance of a CPU?

  • Clock speed: Higher clock speed allows more instructions to be executed per second
  • Number of cores: More cores enable parallel processing of instructions
  • Cache size: Larger cache allows faster access to frequently used data and instructions