- Reading time: 3 minutes
- Price: Free download
- Published: 17th September 2026
- Word count: 858 words
- File format: Text
Why do you want to study this course or subject?
The moment that made me want to study computer systems was fairly unglamorous: a second-hand desktop I bought for twenty pounds refused to boot, and I spent a weekend working out whether the fault was the power supply, the RAM or the drive. It turned out to be a failing hard disk, but what stayed with me was how little I understood about the layers between pressing the power button and seeing a desktop. I had written Python in class for two years without ever asking what a variable actually was in memory. Since then I have been steadily filling that gap. I read Charles Petzold's Code, which builds from relays and logic gates up to a working computer, and it changed how I thought about programming: an if statement stopped being a piece of syntax and became branching in a fetch-decode-execute cycle. I later worked through parts of Nand2Tetris, building logic gates and an ALU in the hardware simulator, and I found the low-level material more satisfying than the higher-level projects I had done before. I want a degree that treats the machine itself as the subject, covering architecture, operating systems, networking and concurrency, rather than one focused mainly on application development. I am also drawn to the fact that systems work has clear constraints: memory is finite, latency is real, and a design either holds up under load or it does not. That combination of theory and measurable consequences is what I would like to spend the next few years on, and eventually I would like to work in infrastructure or embedded systems.
How have your qualifications and studies helped you to prepare?
My A levels in Computer Science, Maths and Physics have each contributed something different. In Computer Science I have covered processor architecture, memory hierarchies, TCP/IP and operating system scheduling, and my coursework project is a command-line tool that indexes text files and answers keyword queries. Building it taught me more about file handling, data structures and testing than any exercise sheet did, particularly when I had to rewrite my index because linear searching through a list became unusable once I had a few thousand entries. Maths has been the most demanding and the most useful. Discrete topics such as logic, modular arithmetic and graphs appear constantly in systems material, and proof by induction gave me a way of reasoning about recursive structures that I now use instinctively. Physics has trained me to build simple models, estimate orders of magnitude and take measurement seriously; electricity and circuits modules gave me the vocabulary to read component datasheets when I was choosing parts for a rebuild. Outside the syllabus I follow up ideas that interest me. After a lesson on caching I read about cache lines and tried timing array traversals in row order and column order in C to see the difference for myself, which was a useful lesson in how much performance depends on layout rather than algorithm alone. I am teaching myself C properly this year, working through exercises on pointers and manual memory management, because I expect to need it for any serious systems work and I would rather arrive with some fluency.
What else have you done to prepare outside of education, and why are these experiences useful?
Most of my practical experience comes from tinkering at home. Over the last two years I have rebuilt three donated PCs, swapping drives, replacing thermal paste and diagnosing faults, and passed two of them on to relatives. I run an old laptop as a home server on Debian, hosting a file share and a backup script that copies my family's photos to an external disk on a schedule. Setting it up meant learning about permissions, cron, static addressing and port forwarding, and I have had to fix it several times, including once when a full disk quietly stopped the backups. Checking logs rather than guessing is a habit I picked up from that. I also set up a simplified Linux desktop for my grandfather, with large fonts, a handful of icons and remote access so I can help him from my room. Explaining an update to him in plain language is harder than writing the configuration, and it has made me more careful about how systems present themselves to the people using them. I work most Saturdays in a bakery, serving customers and handling the till through a busy morning rush, which has taught me to stay accurate when the queue is long and to work with people I did not choose. I also help run a junior badminton session at my local club, warming up a group of eight to eleven year olds and umpiring their matches, which takes patience and quick decisions. Both commitments mean planning my week around fixed hours, and I have learned to protect blocks of time for coursework and for the reading I actually want to do.
This example has 4,638 characters across the three answers. Use it for ideas and structure. Your own UCAS answers must fit within 4,000 characters in total, including spaces.
Why this example works — strengths and ways to improve
This is a specific, credible statement whose evidence is mostly ordinary: a twenty-pound desktop, coursework, a home server. Each piece is tied to real systems understanding. Motivation and academic preparation are especially convincing. The main problem is length. At 4,638 characters it exceeds the 4,000-character UCAS limit, so cuts are essential. The later part of the third answer is where trimming will cost least.
Subject motivation
how little I understood about the layers between pressing the power button
Your opening works because it turns a small fault into a genuine intellectual question about abstraction layers. The Code and Nand2Tetris sentences then show that curiosity being followed up. Your preference for architecture over application development is clear and argued rather than asserted.
Academic preparation
linear searching through a list became unusable once I had a few thousand entries
This is strong evidence because it shows a design decision forced by real behaviour, not just a list of covered topics. Maths and Physics are each linked to systems thinking. The datasheet clause is weaker and repeats your home rebuilding, so it could go.
Evidence and reflection
how much performance depends on layout rather than algorithm alone
Your cache experiment is a good example of reflection: you tested an idea yourself and drew a precise conclusion. Similarly, "Checking logs rather than guessing" names a concrete habit. Most claims are earned by examples rather than generic skill statements.
Relevant experience
a full disk quietly stopped the backups
The home server and your grandfather's desktop are excellent, accessible evidence. Each comes with a lesson about reliability or usability. The bakery and badminton material is honest but more generic, and it reflects on time management at some length. It is the natural place to compress.
Credibility and voice
I would rather arrive with some fluency
Your tone suits a school applicant. You describe learning C, using simulators and fixing your own mistakes without claiming expertise. Phrases like "fairly unglamorous" give a personal voice without ornament. "I now use instinctively" slightly overstates things and could be softened or removed.
Structure and format
This example has 4,638 characters across the three answers.
Each answer comfortably exceeds 350 characters and is well organised. However, the combined total is roughly 640 characters over the 4,000 limit. You will need to cut it, keeping above the library's 3,500 minimum. The career sentence closing the first answer is also somewhat bolted on.
What you’ve done well
- Your hardware failure, Petzold reading and Nand2Tetris work form a coherent, believable path into low-level systems.
- The index rewrite and the array-traversal timing show you learning from measured behaviour, which suits the subject well.
- Your home server and your grandfather's setup show practical responsibility and a thoughtful view of users.
How this draft could improve
- Cut about 640 characters. Start by condensing the bakery and badminton sentences into one line about balancing fixed commitments, rather than describing both in detail.
- Remove the Physics datasheet clause, because rebuilding PCs is already covered in your third answer.
- Trim minor phrases that add little, such as the closing career ambition or "I now use instinctively," to save space and keep claims modest.