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9618 · 16.1

Purposes of an Operating System (OS) — practice questions

Practice and worked examples for 9618 Purposes of an Operating System (OS). Short previews only — attempt the full question in MarkScheme against the official scheme.

Worked example 1

A user connects a new printer to their computer via a USB cable and prints a document. Explain, step-by-step, the role of the operating system in this process.

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Here is a breakdown of the OS's involvement:

  1. Hardware Detection: The OS's Plug and Play (PnP) service detects that a new device has been connected to a USB port.
  2. Driver Identification: The OS queries the printer to identify it. It then checks its own database for a suitable device driver. If a driver is not pre-installed, it may prompt the user to install one from a disk or download it from the internet.
  3. Driver Loading: The OS loads the correct device driver into memory. This driver acts as a translator between the generic 'print' commands from the OS and the specific machine code the printer understands.
  4. Process Management: When the user clicks 'Print', the application sends the print job to the OS. The OS may use a process called spooling, where the print job is saved to a temporary file on the hard disk. This frees up the application immediately, rather than making it wait for the slow printing process to finish.
  5. I/O Management: The OS scheduler sends the spooled data from the hard disk to the printer in the background, via the device driver, managing the flow of data through the USB port without halting other user activities.

Worked example 2

A user is editing a large video file. The editing software becomes unresponsive. The user opens the Task Manager (or Activity Monitor) to close the application. Describe the role of the OS in this scenario.

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  1. Providing System Utilities: The Task Manager is a utility program provided by the OS. It gives the user a view of all currently running processes and their resource consumption (CPU, memory).
  2. Process Identification: The OS lists the video editing software as a process, likely showing high CPU or memory usage and a 'Not Responding' status. This status is determined by the OS when a process fails to respond to system messages.
  3. Handling User Command: When the user selects the process and clicks 'End Task', they are sending a command to the OS.
  4. Process Termination: The OS sends a termination signal to the unresponsive process. It then forcibly deallocates all resources assigned to that process, including reclaiming its allocated RAM and removing it from the CPU scheduler's queue.
  5. System Stability: By terminating the single misbehaving process, the OS prevents it from crashing the entire system, demonstrating its role in maintaining stability.
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