Test Notes

• How the PC is used during the fetch execute cycle

  The PC holds the address of the next instruction. It is executed during the fetch phase.
• Describe the purpose of the clock

  The clock produces pulses for the synchronisation of operations between hardware/internal components.
• explain what happens during the fetch execute cycle

  The instruction is fetched from memory and the PC is used to locate the instruction. It’s then loaded into the IR and the PC is incremented. The CPU decodes the instruction and checks with the IR to ensure it is an instruction that can be carried out. The CPU then executes the instruction.
• Difference between internal memory and secondary storage

  Internal memory is part of the CPU. It consists of RAM/ROM/Cache memory. Secondary storage is external to the CPU e.g magnetic or optical.
• Ways to improve processing speed of PC

  1. Upgrade the processor type e.g parallel processing.
  2. Upgrade the clock to one with a faster clock rate so that more instructions can be executed.
• Describe the main features of WIMP

  Windows - represent an active area of the computer screen which is opened up to display some form of activity

  Icons - small pictures used to provide a graphical representation of an activity.

  Menu - used to represent an end user with a range of options. Groups related actions together.

  Pointer - will move around the screen based on the movements of the end users manipulation of a peripheral device such as a mouse
• Evaluate Command Line and WIMP from POV of experienced user

  • Command Line - There is a preset list of commands. Each command is entered at a prompt and usually includes switches.
  • WIMP - This is a GUI. Each task has its own window containing icons. A pointer and mouse are used to navigate and select icons/menus
  • Experienced user may prefer CLI, as in WIMP a single command may perform a task which would require a long sequence of mouse clicks.
• How can text be input into a smart phone

  Text can be input using a keyboard. The QWERTY keyboard is the most common format available. It will incorporate letters, digits and special characters. Some devices may have a separate numeric keypad. The selection of a key will generate a digital signal representing the character code. When a symbol is printed, the character code is converted.
• Data compression

  The process associated with reducing the memory or storage required by large files. Often important when it comes to data transmission, storage and backing storage devices. It uses a series of algorithms to reduce the amount of real space taken up by data on a storage medium.
• Why are files compressed

  Files are compressed so that information can be easily stored and free up more room so that more files can be saved.
• Software based compression vs Hardware based compression

  Software based compression is often included as a facility of an operating system and readily available on most computer systems. It slows down the process of reading and writing to disk. Hardware based compression requires specialist hardware which can be expensive. It doesn’t affect the speed of access as much as software based compression.
• Lossless compression

  Uses an algorithm that compresses data into a form that may be decompressed at a later time without any data loss, returning the file to its exact original form.
• Lossy compression

  Compresses the file size by discarding some data. It aims to reduce the amount of data that needs to be stored.
• Evaluate Bitmap, JPEG and GIF

  • Bitmap - Each pixel of an image is stored as a pattern which defines its colour using 8/16/32 bits without compression. Good for continuous tone images and produces larger files which take longer to transfer in no loss of detail.
  • JPEG - identifies patterns which are repeated in an image and stored only once. Results in smaller files which transfer more quickly but can lead to reduction in detail.
• GIF

  Developed to support the compression and storage of images using bitmapped data. 8 bits are used to represent data relating to each pixel so only 256 distinct colours are represented. It supports both animated and static images. Compressed to save transmission. However they aren’t ideal for storing digital photos.