What does OCR section 1.2 cover?

Section 1.2 covers software and software development: the functions and types of operating system, applications generation, software development methodologies (waterfall, agile, extreme programming, spiral, rapid application development), the characteristics of high-level and low-level languages and the assemblers, compilers and interpreters that translate them with the stages of compilation, and programming paradigms including procedural and object-oriented programming with its principles of encapsulation, inheritance and polymorphism.

What is the difference between a compiler and an interpreter?

A compiler translates the whole high-level program into machine code at once, producing a fast standalone executable that can be distributed without the source code, but it reports all errors only after translating and is platform-specific. An interpreter translates and executes one statement at a time, reporting the first error as it reaches it, which is convenient for development, but it runs more slowly because code, including statements inside loops, is retranslated each time it executes.

What are the stages of compilation?

There are four stages. Lexical analysis reads the source and groups characters into tokens, removing whitespace and comments and starting the symbol table. Syntax analysis checks the tokens against the language grammar, building a syntax tree and reporting syntax errors. Code generation translates the tree into object code. Optimisation, an optional final stage, improves the code to run faster or use less memory without changing its behaviour.

What are the core principles of object-oriented programming?

A class is a template defining attributes and methods; an object is an instance of a class. Encapsulation bundles attributes and methods together and keeps attributes private, exposing them only through methods, which protects the data. Inheritance lets a subclass reuse and extend a superclass. Polymorphism lets the same method call behave differently depending on the object's actual class, usually through overriding an inherited method.

How should I revise section 1.2?

Learn the five OS types and five methodologies as labelled pairs of merits and uses, because OCR asks you to match them to scenarios. Rehearse the compiler-versus-interpreter comparison across error reporting, speed and distribution, and the four compilation stages in order. For OOP, be able to define encapsulation, inheritance and polymorphism with a worked example each, and read short class definitions in pseudocode or your studied language.

EnglandComputer Science

OCR A-Level Computer Science Software and software development: OS types, translators and OOP made exam-ready

A deep-dive OCR H446 guide to Component 01 section 1.2, software and software development. Covers types of operating system and software development methodologies, translators and the stages of compilation, programming paradigms and the principles of object-oriented programming, and applications generation with the types and uses of software.

Generated by Claude Opus 4.815 min readH446 1.2Updated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section

What this section actually demands
Operating systems, methodologies and translators
Paradigms and software types
How this section is examined
Check your knowledge

What this section actually demands

Section 1.2 is the software half of the systems paper. It rewards precise definitions and applied judgement: matching an operating-system type or a development methodology to a scenario, comparing translators across several criteria, walking through compilation, and defining the object-oriented principles with examples. The marks sit in extended-response comparisons that reach a conclusion.

This guide walks through the topics in order and sets out the exam patterns OCR repeats. Each topic has a matching dot-point page with practice; this overview ties them together.

Operating systems, methodologies and translators

Operating systems and software development methodologies covers the five OS types (distributed, embedded, multitasking, multiuser, real-time) and the five methodologies (waterfall, agile, extreme programming, spiral, rapid application development). The recurring skill is matching one to a project or device and justifying it: embedded OS for a dedicated device, real-time OS for safety-critical control, agile for changing requirements, waterfall for stable regulated ones.

Translators and the stages of compilation covers assemblers, compilers and interpreters with their trade-offs, the four compilation stages (lexical analysis, syntax analysis, code generation, optimisation), and the roles of linkers, loaders and libraries. The classic question compares a compiler and an interpreter across error reporting, execution speed and distribution.

Paradigms and software types

Programming paradigms and languages covers procedural, low-level and object-oriented programming, the high-level versus low-level trade-off, and the OOP principles of classes, objects, methods, attributes, encapsulation, inheritance and polymorphism, which you must define with examples and recognise in short class definitions.

Applications generation and types of software covers how an application is built (compile, link, load), the role of utilities, the systems-versus-application distinction, and the open-source versus closed-source and off-the-shelf versus custom-written trade-offs, set as discussion questions tied to an organisation.

How this section is examined

A typical OCR profile for section 1.2:

Scenario matching. Pick an OS type or methodology for a device or project and justify it.
Translator comparison. Compiler versus interpreter across error reporting, speed and distribution; the four compilation stages.
OOP definitions. Define encapsulation, inheritance and polymorphism with a worked example each.
Software-choice discussion. Open source versus closed source, off-the-shelf versus bespoke, resolved with a recommendation (levels of response).

Check your knowledge

A mix of recall and applied questions covering the section. Attempt them under timed conditions, then check against the solutions.

State the type of operating system essential for a car's anti-lock braking system. (1 mark)
Name the methodology that builds working software in short iterations welcoming changing requirements. (1 mark)
State what is produced by the syntax analysis stage of compilation. (1 mark)
Explain why interpreted code is generally slower than compiled code. (2 marks)
Define polymorphism in object-oriented programming. (2 marks)
State one advantage of off-the-shelf software over bespoke software. (1 mark)

Solutions

Q1: A real-time operating system, because it must guarantee a response within a strict deadline.
Q2: Agile (extreme programming is also acceptable as a specific agile methodology).
Q3: A syntax (parse) tree, with syntax errors reported and the symbol table completed; the tokens are checked against the language grammar.
Q4: Each statement is translated every time it is executed (statements inside loops are retranslated on every pass), whereas compiled code is translated once into native machine code that then runs directly.
Q5: Polymorphism is when the same method call behaves differently depending on the object's actual class, typically because a subclass overrides an inherited method.
Q6: Any one of: cheaper, immediately available, thoroughly tested by a large user base, well documented and supported.

Sources & how we know this

OCR AS and A Level Computer Science (H046, H446) specification — OCR (2015)