SQA National 5 Computing Science: a complete overview of Computer systems
A deep-dive SQA National 5 Computing Science guide to Computer systems. Covers data representation and units of storage, computer architecture (processor, memory and buses), the environmental impact of computer systems, and security risks, precautions and the Computer Misuse Act.
Reviewed by: AI editorial process; not yet individually human-reviewed
Jump to a section
Computer systems is examined in Section 1 of the National 5 Computing Science question paper, alongside Software design and development. It covers how a computer stores data, how its hardware is organised, and the environmental and security issues that come with using computers. This guide maps each key area; each has its own answer page with worked examples.
Data representation and units of storage
Computers store everything in binary. A positive integer uses binary place values (128, 64, 32, ...); a real number uses floating point (a mantissa for the digits and an exponent for the point position); a character is stored as a code number from a set such as ASCII. Storage is measured in bits (a single 0 or 1) and bytes (8 bits), scaling up through kilobyte, megabyte, gigabyte and terabyte, each about 1000 times the one below.
Computer architecture
The processor carries out instructions using its arithmetic logic unit (calculations and comparisons), its control unit (directing the system) and registers (fast small stores). Main memory holds the instructions and data in use. Buses connect them: the address bus carries the location of data and the data bus carries the data itself.
Environmental impact
Computer systems have an impact across their life: manufacture uses energy and materials, use consumes electricity, and disposal creates e-waste. The impact can be reduced by recycling and reusing equipment, using low-power settings, and keeping devices longer.
Security risks, precautions and the law
Systems face risks such as malware, hacking and data theft. Precautions include strong passwords, biometrics (fingerprint or face), anti-virus software and encryption (scrambling data with a key so only an authorised person can read it). The Computer Misuse Act makes unauthorised access to a computer system a criminal offence.
How Computer systems is examined
Expect recall and short-explanation questions: how data is stored, the order of storage units, the roles of processor, memory and buses, the environmental impact and how to reduce it, and security risks matched to precautions. Learn the vocabulary precisely (mantissa and exponent, address bus and data bus, encryption needs a key) and match each precaution to the risk it addresses.
For the official course specification
The SQA publishes the full National 5 Computing Science course specification, specimen question papers and coursework tasks at sqa.org.uk. Always revise from the current specification and SQA past papers.