AQA A Level Computer Science Revision Questions and Answers

List two components with which the CPU works to execute program instructions. Memory Input and Output Devices Describe the role of the Control Unit in the fetch-decode-execute cycle. The control unit coordinates the actions of the computer. It sends out control signals to other parts of the CPU and to other components of the computer. State the function of the Program Counter. This holds the address of the next instruction to be fetched. State the function of the Memory Data Register (MDR). The MDR is temporary store(buffer) for anything copied from memory. State the function of the Accumulator. The accumulator is a temporary store for the results of calculations carried out by the ALU. State two components of Von Neumann's design in addition to the CPU. Memory to store program data and instructions. Input and output devices. Define the term "stored program concept" A computer in which the program instructions and the data are stored in memory. State the role of RAM in the fetch-decode-execute cycle. RAM is where the program instructions and data are stored until they are needed. Describe what is meant by a register. A register is a memory location within the CPU used to store program instructions and/or data. Explain why cache memory is used in the CPU. The cache consists of very fast memory and it is used to store frequently used commands and data. These can be accessed more quickly from the cache than from the slower RAM when they are needed. The performance of a CPU can be improved by increasing its clock speed. Explain why performance cannot be increased indefinitely by increasing the clock speed. Performance cannot be improved indefinitely because the rate at which the transistors process the instructions is limited.