Ocr As Level Computer Science H046/01: Paper 1 June 2023 Final Mark Scheme Computing Principles

Accumulator (ACC). Hold the data currently being processed by the CPU. Data is placed in the ACC before and after being processed by the ALU. {Ans: Explain what the ACC does.}Cheaper than most forms of storage. Non-volatile. Moderate capacity. Disks are light and portable. Slow data transfer rate - hence generally better suited to domestic uses rather than large-scale commercial ones. Disks can easily scratch. E.g. CD-ROM - data is written during the manufacturing process. E.g. CD-R/DVD-R - data can be written by the user but only once. E.g. CD-RW/DVD-RW - data can be written and rewritten by the user. {Ans: Describe the properties of Optical storage devices. Include an example.}High data transfer rate. Non-volatile. Large capacities. Not portable - contains moving parts that may break if moved. Can be noisy. E.g. Hard Disc Drives (HDDs): Used as permanent storage for the computer's main files. {Ans: Describe the properties of Magnetic storage devices. Include an example.}Current Instruction Register (CIR). Contains the instruction to be decoded (before it is executed), copied from the MDR. The CIR splits the instruction into two parts: - The opcode is the instruction/operation to be carried out (e.g. ADD) - The opcode is