Computer Science Paper 1 Practice Questions and Answers

Control Unit A register in the cpu that controls and coordinates the activities of the cpu directing the flow of data Bus a series of connectors that transfer signals between internal components Memory Read causes data from the addressed location in RAM to be placed on the data bus Memory Write Causes data on the data bus to be written into the addressed location. Bus Request Indicates that a device is requesting the use of the data bus Bus Grant Indicates that the CPU has granted access to the data bus. System bus collective term for address, data and control bus Data bus A bi-directional path for moving data and instructions between system components Clock used to synchronize operations Control bus A bi-directional bus to transmit command, timing and specific status information between system components Address bus A one directional bus that transmits memory addresses that are used as operands in programming instructions, so that data can be retrieved from main memory ALU Arithmetic-Logic unit, preforms logical and arithmetic operations on data e.g. ADD, SUBTRACT, shift operations or Boolean logic Registers High speed memory cells, all arithmetic and logic happens in these, typically there are 16 general purpose registers in a CPU, they are very fast Accumulator A special purpose register which stores the result of calculations made by the ALU