The FDE Cycle & CPU

• The CPU is known as the 'brain of the computer'
• The purpose of the CPU is to process data, which includes searching, sorting, calculating, and decision making
• The CPU follows the Fetch - Decode - Execute cycle to process data
• In the Fetch stage, the CPU fetches data and instructions from RAM and stores them in its temporary memory called 'registers'
• The CPU uses the 'address bus' to fetch data from RAM and the 'Data Bus' to transfer data to the CPU
• In the Decode stage, the CPU understands and works out what the fetched instruction means
• The Execute stage is where data processing happens and instructions are carried out on the data
• All Von Neumann CPUs have an instruction set with simple instructions like ADD, SUB, STA, LDA, BRA, and OUT
• Registers used during each Fetch-Decode-Execute cycle include the Accumulator (A), Program Counter (C), Memory Address Register (MAR), Instruction Register (IR), and Memory Data Register (MDR)
• Registers are tiny memory locations used to carry out instructions in a typical F-D-E cycle
• The Von Neumann architecture allows data and instructions to be held together in memory and executed one at a time without rewiring the circuitry of the machine
• Computer scientists invented a simple coding language to make programming software accessible to the masses