Singapore GCE O-Level Computing (7155): complete 2026 guide to the seven topics and Papers 1-2

Singapore GCE O-Level Computing (SEAB syllabus 7155) is a Secondary 3 to 4 course that builds the foundations of computing: how data is represented in binary, how to process information in spreadsheets, how to design algorithms and write working programs in Python, and how networks, computer systems and security shape the way we use technology.

This page is the index. Below: the seven topic-area breakdown, the two-paper assessment structure (a written Paper 1 and a lab-based practical Paper 2), study strategy, and links to every dot-point answer we have shipped for O-Level Computing in 2026.

The topics of O-Level Computing

Data Representation

Why computers use binary, place value in binary and hexadecimal, converting between binary, denary and hexadecimal, binary addition and overflow, and how text, sound and images are stored as numbers along with units of storage and basic compression.

Spreadsheets and Data Processing

Cells, rows, columns and formulae, relative and absolute references, common functions such as SUM and AVERAGE, logical and lookup functions such as IF and VLOOKUP, and turning data into charts with sorting and filtering.

Algorithms and Problem Solving

Designing solutions with flowcharts and pseudocode, the building blocks of sequence, selection and iteration, linear and binary search, bubble sort, and checking a design with trace tables and test data.

Programming in Python

Variables and data types, selection with if and elif, iteration with for and while, defining functions and procedures, and working with lists and strings to build and test complete programs.

Networks and the Internet

Types of network such as LAN and WAN, the internet and the World Wide Web, IP addresses and protocols, the threats networks face, and the measures used to protect them.

Computer Systems and Architecture

The difference between hardware and software, the role of the CPU and the fetch-execute cycle, main memory and secondary storage, and input, output and peripheral devices.

Security, Ethics and the Impact of Computing

Cyber threats and malware, protecting data and privacy, the laws and ethics that govern computer use, and the social and environmental impact of computing.

Assessment structure

O-Level Computing 7155 is assessed across two papers that together cover theory and practical skills.

• Paper 1: Written (theory). A written paper sat on paper covering the whole syllabus with short-answer and structured questions. It tests understanding of data representation, algorithms, networks, computer systems and security, including tracing algorithms and converting between number bases by hand.
• Paper 2: Lab-based practical. A hands-on paper sat at a computer. You are given tasks to solve using spreadsheet software and Python, and you are marked on whether your working solution produces correct results and is clearly structured and tested.

Both papers reward clear, logical working. Paper 1 rewards precise definitions, correct trace tables and accurate conversions; Paper 2 rewards solutions that actually run, handle the given data, and are tested against sensible cases. Always confirm the exact paper format and weightings against the current syllabus year.

Study strategy

O-Level Computing rewards understanding combined with regular hands-on practice. The recipe:

1. Practise the practical at a keyboard. Paper 2 cannot be revised by reading alone. Re-build spreadsheet tasks and write small Python programs from scratch every week so the syntax and the software become automatic.
2. Design before you code. Sketch a flowchart or write pseudocode first, then translate it to Python. A clear plan makes the code shorter and the logic easier to test.
3. Trace and test everything. Walk through algorithms with a trace table by hand, and always test programs with normal, boundary and invalid data. Most marks lost in Computing come from logic errors a quick trace would catch.
4. Drill the conversions. Binary, denary and hexadecimal conversions and binary addition appear every year. Practise them until they are quick and reliable so the written paper time goes to thinking, not arithmetic.

Our 2026 O-Level Computing syllabus answers

Every O-Level Computing learning point we have shipped has its own focused answer page with worked exam-style questions and cross-links to related points.

Browse the full set at /sg-o-level/computer-science/syllabus.

For the official syllabus

SEAB publishes the full 7155 syllabus document and examination requirements at seab.gov.sg. Always confirm content and assessment weightings against the current syllabus year, as SEAB reviews syllabuses periodically.