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The homepage for all content aimed at Key Stage 3 students studying Computer Science / IT including computer hardware, Python, App Inventor 2 and Cyber Security. Key Stage 3 Topics This section will be updated over the summer for a new look and more topics in September 2025. = Updated Hardware Python Basics 1. The Motherboard 2. The CPU 3. Memory 4. Expansion Cards 1. The Basics 2. Variables 3. Inputs 4. Calculations 5. Selection 6. Turtle 7. Link to GCSE Python Cyber Security 1. Malware 2. Phishing & Staying Safe Desktop Publishing (DTP) Desktop Publishing

Learn about key registers used in the fetch - execute cycle such as the program counter and current instruction register. Based on the J277 OCR GCSE Computer Science specification (first taught from 2020 onwards). 1.1b: Registers & The F-E Cycle Exam Board: OCR Specification: J277 Watch on YouTube : Registers in the FE Cycle Reading instructions The fetch - execute (F-E) cycle is performed by the CPU millions of times every second. This cycle is how the CPU processes data and instructions for each program or service requiring attention . Important Registers A register is a small storage space for temporary data in the CPU . Each register has a specific role . There are four essential registers used in the F-E cycle : Program Counter (PC) A register that tracks the RAM address of the next instruction to be fetched . Memory Address Register (MAR) Stores the RAM address of the current instruction (or data ) the CPU needs to access . Memory Data Register (MDR) The MDR stores the instruction that has been transferred from RAM to the CPU . Accumulator (ACC) The ACC stores the result of mathematical or logical calculations . The PC , MAR and MDR are used in the fetch stage , whereas the ACC is used in the execute stage . The PC and MAR store an address (a memory location in RAM ) whereas the MDR and ACC store data (a value ). Fetch - Execute Cycle The essential idea of the F-E cycle is that instructions are fetched from RAM , to be decoded (understood) and executed (processed) by the CPU . 1. The Program Counter (PC ) register displays the address in RAM of the next instruction to be processed . This value is copied into the Memory Address Register (MAR ). 0054 2. The PC register is increased by 1 . This prepares the CPU for the next instruction to be fetched. 0055 3. The CPU checks the address in RAM which matches the address held in the MAR . 0054 4. The instruction in RAM is transferred to the Memory Data Register (MDR ). MDR 5. The instruction is decoded by the contol unit which splits the instruction into an opcode (an action ) and an operand ( data or address ). 6. The instruction i s executed (run). Any result of an execution is stored in the Accumulator (ACC ) register, such as calculations made by the ALU . ACC 7. The cycle repeats by returning to the first step and checking the program counter for the address of the next instruction . Q uesto's Q uestions 1.1b - Registers & The F-E Cycle: 1 . What is the purpose of the registers ? [1 ] 2 . Describe the purpose of each register : a. The Program Counter (PC) [ 2 ] b. The Memory Address Register (MAR) [ 2 ] c. The Memory Data Register (MDR) [ 2 ] d. The Current Instruction Register (CIR) [ 2 ] e. The Accumulator (ACC) [ 2 ] 3. Draw a diagram with icons and words to show the steps of the Fetch - Execute cycle . [7 ] 1.1a - The CPU Theory Topics 1.2 - CPU Performance

Based on the 2015 OCR Computer Science A-Level specification. Exam Board: OCR 1.3a: Input & Output Devices Specification: A-Level 2015 An instruction set is a list of all the instructions that a CPU can process as part of the FDE cycle . CPUs can have different sets of instructions that they can perform based on their function. The two most common instruction sets are the simpler RISC (Reduced Instruction Set Computer ) and more complicated CISC (Complex Instruction Set Computer ). Instruction Sets This page is still being updated. Graphical Processing Unit What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Multicore & Parallel Systems What is cache memory? Cache memory is temporary storage for frequently accessed data . Cache memory is very quick to access because it is closer to the CPU than other types of memory like RAM . Q uesto's Q uestions 1.3a - Input & Output Devices: 1. What is cache memory ? [ 2 ] 1.2 Processors Theory Topics 1.3b - Memory & Storage