System Software
System software is the software that manages a computer's hardware and resources and provides a platform for applications to run, made up mainly of the operating system and utility software. It is assessed in Paper 1 of GCSE Computer Science, covering OS functions such as memory and process management plus utilities like defragmentation, compression and encryption.
Before you start
Make sure you're comfortable with these topics first:
Method
- Learn the main functions of an operating system: memory management, process/processor scheduling, peripheral management via device drivers, user management and providing the user interface.
- Explain how the OS uses virtual memory to manage RAM when it becomes full, and the drawback of relying on it too heavily.
- Learn what an interrupt is and why interrupts are given different priority levels.
- Learn the purpose of common utility software: defragmentation, encryption and compression, and the difference between lossy and lossless compression.
- Practise run-length encoding (RLE) style questions: encoding runs of repeated data and calculating compression ratios.
- Practise tracing simple scheduling algorithms such as round robin and first come first served.
Worked example
A row of 10 pixels in a black and white image is: BBBBBWWWWW. (a) Use run-length encoding to encode this row as pairs of (colour, run length). (b) Each pair is stored using 2 bytes. Calculate the compression ratio, given that the uncompressed row (1 byte per pixel) uses 10 bytes.
- Identify the runs of identical colours in order: 5 black pixels, then 5 white pixels.
- Write each run as a (colour, run length) pair: (B,5), (W,5).
- Calculate the compressed size: 2 pairs x 2 bytes each = 4 bytes.
- Compare this to the uncompressed size of 10 bytes.
- Express this as a ratio: 10 : 4, which simplifies to 2.5 : 1.
- Final answer: RLE encoding is (B,5)(W,5); the compression ratio is 2.5 : 1.
Practice questions
Try each question, then tap to reveal the answer.
Exam-style questions
Written in the style of a GCSE Computer Science exam paper, with a full mark scheme.
Using an example, explain how memory management carried out by the operating system lets a computer run more than one program at the same time.
After a user leaves many browser tabs and a large video editing program open at the same time, their computer becomes extremely slow. Using the concept of virtual memory, explain why this has happened.
A UK estate agent wants to back up property photos to an external hard drive every week, and also email some finished images to clients. The agent is considering using compression software and encryption software as part of this process. Discuss how each type of software could be used in this scenario, and evaluate whether the agent needs both, one, or neither.
Free printable worksheet
Want more practice on paper? Download the system software worksheet pack - 16 pages of exam-style questions with a full mark scheme. No sign-up, no email wall - just the PDF, free for personal and classroom use.
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