OCR · J277
OCR GCSE Computer Science
41 topics and 607 questions in OCR's style.
The two papers
- J277/01 Computer systems. 80 marks, 90 minutes.
- J277/02 Computational thinking, algorithms and programming. 80 marks, 90 minutes.
Questions show code in OCR Exam Reference Language. Your own answers can be in it or a high-level language.
Algorithms OCR Paper 2
- 2.1.1, 2.1.2LessonPractice
Abstraction, decomposition and algorithms
- Explain what an algorithm is and that a program implements one
- Use abstraction and decomposition on a problem, with a structure diagram
- Name the inputs, processes and outputs of a problem or algorithm
- 2.1.2LessonPractice
Flowcharts, pseudocode and trace tables
- Read and draw flowcharts with the standard symbols
- Complete a trace table for a short algorithm
- Work out what a simple algorithm is for
- 2.1.3LessonPractice
Linear and binary search
- Run a linear search and a binary search by hand
- State that binary search needs sorted data
- Compare the two searches, including how many comparisons each makes
- 2.1.3LessonPractice
Bubble sort and merge sort
- Show the list after each pass of a bubble sort
- Show how a merge sort splits and merges a list
- Compare bubble sort and merge sort for time and memory
- 2.1.3LessonPractice
Insertion sort
- Show the list as each item is inserted into the sorted part
- Compare insertion sort with bubble and merge sort
Programming OCR Paper 2
- 2.1.2, 2.2.1, Section 3cLessonPractice
Reading OCR Exam Reference Language
- Read = for assignment and == for comparison, const and global
- Read for ... next, while, do ... until, if ... elseif and switch
- Use .substring(start, count), .left, .right, .length, .upper and .lower
- 2.2.2LessonPractice
Data types and casting
- Choose integer, real, Boolean, character or string for a piece of data
- Convert between strings and numbers, and say when a program must
- 2.2.1, 2.2.3LessonPractice
Variables, constants, operators and input
- Use variables and constants, and explain why a named constant helps
- Evaluate expressions with +, -, *, /, DIV, MOD and comparisons
- Take input, give output and generate random numbers
- 2.2.1LessonPractice
Selection and Boolean conditions
- Trace IF, ELSE IF and nested selection
- Combine conditions with AND, OR and NOT
- Choose test values that reach every branch
- 2.2.1LessonPractice
Count-controlled and condition-controlled loops
- Trace count-controlled loops, including STEP
- Trace loops with the condition at the start or the end
- Trace nested loops and count how often a line runs
- 2.2.3LessonPractice
String handling
- Find a string's length, a character's position and a substring
- Join strings and convert between characters and character codes
- 2.2.3LessonPractice
Arrays and records
- Read and update one-dimensional and two-dimensional arrays
- Total, search and count through an array with a loop
- Use a record to keep related fields together
- 2.2.3LessonPractice
Procedures, functions and parameters
- Tell a procedure from a function and trace a call
- Pass data in with parameters and out with a return value
- Explain local and global variables and why structured code helps
- 2.2.3LessonPractice
Reading and writing files
- Open, read, write and close a text file
- Read a file line by line until its end
- 2.3.1LessonPractice
Validation, authentication and maintainable code
- Write a range, length or presence check
- Write a simple username and password check
- Explain how naming, indentation, comments and subroutines help maintenance
- 2.3.2LessonPractice
Testing and errors
- Choose normal, boundary and erroneous (invalid) test data
- Tell a syntax error from a logic error and fix it
- Complete a test plan; tell iterative from final testing
- 2.5.2LessonPractice
The IDE
- Name the IDE tools: editor, error diagnostics, run-time environment and translator
- Explain how each tool helps a programmer
Data representation OCR Paper 1
- 1.2.3LessonPractice
Bits, bytes and storage units
- Use bit, nibble, byte and the prefixes kilo to peta
- Convert between units and compare quantities of data
- Work out how much storage a set of files needs
- 1.2.4LessonPractice
Binary, denary and hexadecimal
- Convert between binary, denary and hexadecimal from 0 to 255
- Explain why hexadecimal is used
- 1.2.4LessonPractice
Binary addition and shifts
- Add binary numbers of up to 8 bits and spot overflow
- Apply logical left and right shifts and say what they do to the value
- 1.2.4LessonPractice
Characters, ASCII and Unicode
- Use a character set table and the order of its codes
- Explain the number of characters a number of bits allows
- Compare ASCII and Unicode
- 1.2.4LessonPractice
Bitmap images
- Explain pixels, resolution and colour depth
- Calculate an image's file size
- Turn a bit pattern into a bitmap and back
- 1.2.4LessonPractice
Sound
- Explain sampling, sample rate and bit depth (sample resolution)
- Calculate a sound file's size and the effect of each setting
- 1.2.5LessonPractice
Why and how data is compressed
- Explain why files are compressed
- Compare lossy and lossless compression for a given use
Computer systems OCR Papers 1 and 2
- 1.1.1LessonPractice
The CPU and the fetch-execute cycle
- Describe the ALU, control unit, clock, registers, cache and buses
- Describe the fetch, decode and execute stages
- 1.1.1LessonPractice
Von Neumann architecture and registers
- Describe the program counter, MAR, MDR and accumulator
- Tell a register that holds an address from one that holds data
- 1.1.2, 1.1.3LessonPractice
CPU performance and embedded systems
- Explain how clock speed, cores and cache size affect performance
- Describe embedded systems and give examples
- 1.2.1LessonPractice
RAM, ROM, cache and virtual memory
- Compare RAM and ROM, and explain volatile and non-volatile
- Explain what cache and registers are for
- Explain why and how virtual memory is used (OCR)
- 1.2.2LessonPractice
Secondary storage and the cloud
- Explain why secondary storage is needed
- Compare magnetic, solid state and optical storage on capacity, speed, portability, durability, reliability and cost
- Compare cloud and local storage
- 2.4.1LessonPractice
Logic gates and truth tables
- Give the truth tables for AND, OR and NOT
- Complete truth tables for circuits of up to three inputs
- Draw a circuit from a Boolean statement and the reverse
- 1.5.1, 1.5.2LessonPractice
Operating systems and utility software
- Tell hardware from software, and system from application software
- Describe what an operating system manages
- Explain what encryption, defragmentation and compression utilities do
- 2.5.1LessonPractice
Programming languages and translators
- Compare high-level and low-level languages, machine code and assembly
- Compare compilers and interpreters
- Explain what an assembler does (AQA)
Networks and cyber security OCR Paper 1
- 1.3.1LessonPractice
Types of network
- Describe LANs and WANs, and PANs (AQA)
- Give the advantages and disadvantages of networking computers
- Explain what affects a network's performance (OCR)
- 1.3.1LessonPractice
Network hardware, the internet and topologies
- Describe routers, switches, wireless access points, NICs and transmission media
- Explain DNS, hosting, the cloud, and web servers and clients
- Compare client-server with peer-to-peer, and star with mesh topologies
- 1.3.2LessonPractice
Wired and wireless connections
- Compare wired and wireless networks and choose one for a scenario
- Describe Ethernet, Wi-Fi and Bluetooth
- Describe IP and MAC addresses (OCR)
- 1.3.2LessonPractice
Protocols and layers
- Explain what a protocol and a standard are
- Give the purpose of TCP, IP, HTTP, HTTPS, FTP, POP, IMAP and SMTP
- Explain why protocols are layered; name the four TCP/IP layers (AQA)
- 1.4.1LessonPractice
Cyber security threats
- Describe malware: viruses, trojans and spyware
- Describe social engineering: phishing, blagging and shouldering
- Describe brute-force, denial of service, interception, SQL injection and pharming
- 1.4.2LessonPractice
Preventing attacks
- Explain penetration testing, firewalls, anti-malware, access levels and passwords
- Explain encryption, physical security, biometrics, CAPTCHA, email confirmation and automatic updates
- Match a prevention method to a threat
Databases, ethics and law OCR Papers 1 and 2
- 2.2.3LessonPractice
SQL: finding data
- Write SELECT ... FROM ... WHERE queries
- Sort results with ORDER BY and join two tables (AQA)
- 1.6.1LessonPractice
Ethical, legal, cultural and environmental impacts
- Discuss the impacts of digital technology on people and the environment
- Weigh privacy against security in a scenario
- Write a balanced extended answer
- 1.6.1LessonPractice
Computer law and software licences
- Explain the Data Protection Act 2018, Computer Misuse Act 1990 and Copyright, Designs and Patents Act 1988
- Compare open source and proprietary licences