The Operating System*

• What is batch processing?

  Processing a large number of instructions, traditionally during hours where processing usage is at its lowest and without user interaction.
• How does batch processing work?

  Data is temporarily stored in a transaction file over a short period of time until stored in a master file which is executed.
• What is a single-user OS?

  An operating system designed to be used by only one user at a time. Each user has its own home directory.
• What is a multi-user OS?

  An operating system that is run on multiple computers or servers to allow multiple people to use simultaneously.
• What is multi-tasking?

  Process of swapping applications in and out of the CPU.
• What is multi-programming computer system?

  Stores multiple instructions "jobs" in main memory at the same time to fasten processing.
• What is a scheduler programme?

  It schedules the jobs slots of time to access the CPU.
• What is a real-time OS?

  The OS responds immediately to inputted data. However, this specialises over specific application software.
• What are interrupts?

  The scheduler sets an instruction or job to be next to be executed, setting all other jobs a new time slot.
• What is a buffer?

  A buffer is a temporary storage area that holds data while it is waiting to be executed.
• What is double buffering?

  Using multiple buffers to store multiple jobs.
• What is and the role of the kernel?

  The kernel is the core component of an operating system. It manages system resources, provides an interface for applications, and facilitates communication between hardware and software.
• What is memory addressing?

  Assigning a location for data in memory.
• How many locations are in memory?

  Number of BYTES
• What is memory partitioning?

  Dividing the computer's memory into separate sections for different purposes.
• What is single-partition allocation?

  Assigning the entire memory to a single process. Relocation-register scheme is used to protect user processes from each other and from changing operating-system code.
• What is multiple-partition allocation?

  Main memory is divided into a number of fixed-sized partitions where each partition should contain only one process. When a partition is free, a process is selected from the inputted queue and loaded into the free partition.
• What are the three process states?

  • Running - when the process has control of the CPU.
  • Ready to run - the process is in the queue waiting for the CPU.
  • Blocked - process is waiting on an input or output operation.
• What are the three running processes?

  • Complete the task and close - scheduling stops and the process stops.
  • Be interrupted by the scheduler - the process is swapped out of the CPU and placed in the ready to run queue.
  • Become blocked - it is moved to the blocked queue, typically to prevent wasting CPU time.
• What is the process control block?

  Data structure used to store the contents of the registers:

  • Program Counter Register, stores the point the process reached.
  • General purpose registers, temporary values used by the process. These values need to be saved as it could be overwritten.
  • Accumulator, stores the result of the last calculation.
  • Variables and state of the process, any variables linked to the process.
  • Priority and process ID, used by the scheduler for administration.
• What does it mean by recording interrupts?

  An interrupt register stores data of bits which represent interrupts. When a bit is set to 1, it is needed to be processed. If multiple interrupts are set to 1, then interrupts could have multiple 1s assigned to rank priority of execution.
• How do interrupts work?

  At the end of the F-D-E cycle, the CPU will look through the interrupt register for flags set and depending on priority of execution, the highest priority instruction will be executed. When an interrupt occurs, all registers are copied onto a stack data structure so the jump protocol can operate on the interrupt.
• What is time slicing?

  Where each user is given a set amount of time, for processing.
• What is polling?

  It is asking a device for its status such as the process of waiting for inputted or outputted data.
• What is threading?

  A mini-process of a broken up process.
• What are disadvantages of threading?

  • Have no control over order of threads to be executed.
  • Programming this can be challenging.
  • Certain threads may need other threads to be executed.