AQA A LEVEL COMPUTER SCIENCE Study guides, Class notes & Summaries

Arithmetic Logic Unit (ALU) - Answer The part of the central processing unit that performs arithmetic computations and logical operations Control Unit - Answer Coordinates activities in the CPU, memory and peripherals Clock - Answer A continuous sequence of clock pulses to step the control unit through its operations Registers - Answer Very fast memory stored on or near the processor Program Counter (PC) - Answer Holds the address of the next instruction to be executed C...

What is a bus? - Answer A set of parallel wires connecting two or more components of a computer What are the three computer buses and what do they do? - Answer - Address Bus carries addresses sent by the processor to access particular memory locations - Data Bus carries data from memory - Control Bus carries control signals What are examples of some control signals? - Answer - Memory write - Memory read - Interrupt request - Clock What is a word of data? - Answer A word is...

What is an integer? - Answer A positive or negative whole number What is a Real or Float number? - Answer A positive or negative number that can have a fractional part. What is a Boolean? - Answer True or False What is a character? - Answer A single letter, number or symbol What is a string? - Answer A group of characters What is Date/Time? - Answer A way of storing Date/Time What is a pointer? - Answer A way of storing a memory address. What is a record? - Ans...

Abstract data type (ADT) - Answer A data type whose properties are specified independently of any particular programming language. Abstraction - Answer Representation that is arrived at by removing unnecessary details. Algorithm - Answer A sequence of unambiguous instructions for solving a problem. Asynchronous serial data transmission - Answer Transmission system in which the sender and receiver have separate clocks which are not kept synchronised. Instead, the clocks are synch...

recursive subroutine [1] - Answer a subroutine that calls itself base case [1] - Answer the circumstances when a recursive subroutine does not call itself components of a stack frame [4] - Answer local variables; return address; parameters; register values; static data structure [3] - Answer fixed storage size determined at compile time; can waste storage space if the number of data items stored is small relative to the size of the structure; store data in consecutive memor...

Data - Answer A general term for facts and figures. Before items of data are input into a computer system, they have not been processed or organised. Information - Answer Data that has been processed or organised by the computer. It is the output from a computer system. Data processing - Answer The process of transforming data into information. Happens inside the computer. Constant - Answer The same as variables except their initial assigned value cannot be changed during the pr...

Define algorithm - Answer An algorithm is a sequence of steps that can be followed to complete a task. Define decomposition - Answer Decomposition means breaking a problem into a number of sub-problems, so that each subproblem accomplishes an identifiable task, which might itself be further subdivided. Define abstraction - Answer Abstraction is the process of removing unnecessary detail from a problem. How does a linear search of an array work? - Answer The search begins wi...

Hardware - Answer A generic term for the physical parts of the computer, both internal and external. AND gate - Answer Output will only be ON if BOTH inputs are ON NOT gate - Answer Inverts the input e.g. Output OFF if the input is ON System Software - Answer A range of programs that are concerned with the more technical aspects of setting up and running the computer e.g. Utility programs, translators, OS Operating System - Answer A suite of programs designed to control the...

Control Unit - Answer A register in the cpu that controls and coordinates the activities of the cpu directing the flow of data Bus - Answer a series of connectors that transfer signals between internal components Memory Read - Answer causes data from the addressed location in RAM to be placed on the data bus Memory Write - Answer Causes data on the data bus to be written into the addressed location. Bus Request - Answer Indicates that a device is requesting the use of the d...