AP Computer Science A Terminology, Exams of Computer Science

Download AP Computer Science A Terminology and more Exams Computer Science in PDF only on Docsity! AP Computer Science A revised test * questions and answers*  Accessor method - Correct answer a method that accesses an object but does not change it  actual parameter - the expression supplied for a formal parameter of a method by the caller  address - Correct answer a location in memory at which a binary number (usually a byte, or value of 8 bits) is stored. The location in memory can itself be identified by a binary number - this number, the absolute or explicit address, gives the absolute location of the address in memory, while a relative address specifies a location memory (some other address only in relation to the current, or base, address. All access to memory is access to to a cell of memory found at a specified address.  algorithm - Correct answer a well-ordered collection of unambiguous and effectively computable operations that, when executed, produces a result and halts in a finite amount of time  [[an unambiguous, executable, and terminating specification of a way to solve a problem  argument - Correct answer an actual parameter in a method call, or one of the values combined by an operator]]  arithmetic/Logic Unit (ALU)  ASCII - Correct answer The American Standard Code for Information Exchange - a character-encoding scheme based on the English alphabet used to represent text in computers. It uses 8 bits to represent each character, so it is able to encode a total of 2^8 = 256 different characters. These are assigned the integer values 0 to 255. Only 32 to 126 have been assigned to printable characters. The ASCII has been largely supplanted by UNICODE and the UCS (universal character set), which are backwards compatible with it (commonly encoded using UTF-8, UTF-16, and UTF-32 representing character sets using 8, 16, and 32 bits respectively. UTF-16 can represent 65,536 characters.)  binary - Correct answer the binary, or the base-2, positional numbering system represents numerical values using only two symbols, 0 and 1  bit - Correct answer a contraction of binary digit; the smallest unit of information, having two possible values: 0 and 1. A data element consisting of n bits has 2ⁿ possible  boolean - Correct answer a data type with two possible value representing true and false.  boolean expression - Correct answer an expression in a programming language that produces a boolean value when evaluated, i.e., true or false  boolean operator - Correct answer an operator that can be applied to Boolean values. Java has 3 boolean, or logical, operators: &&, ||, and !.  byte - Correct answer a number made up of 8 bits. Essentially, all currently manufactured computers use a byte as the smallest unit of storage in memory  cache memory - Correct answer a special, super-high-speed memory unit. Operating on the principle of locality, which says that when the computer uses something it will probably use it again very soon, when the computer references a piece of data for the first time, it stores that data in cache memory, and when it needs to fetch a piece of information, it first looks in cache memory before performing a memory fetch. Since accessing cache memory is so much faster (typically 5 to 10 times faster) than accessing RAM, it is still faster to access cache memory first and then look in RAM if the data is not found (the cache hit rate tells us just how much faster).  cast - Correct answer Explicitly converting a value from one type to a different type  class - Correct answer a programmer defined data type, may be a blueprint or template for creating an object  computer - Correct answer the study of algorithms, including their formal and mathematical properties, their hardware realizations, their linguistic realizations, and their applications  constructor - Correct answer A set of statements for initializing a newly instantiated variable  control unit - Correct answer Unit within the computer that actually carries out the operations of a program. the control unit does three things: fetches from memory the next instruction to be executed, decodes it, and executes it by issuing the appropriate command to the  Memory is divided into fixed-size units called cells, and each cell is associated with a unique identifier called an address. These addresses are the unsigned integers 0, 1, 2, ... , MAX.  All accesses to memory are to a specified address, and we must always fetch or store a complete cell - that is, all the bits in that cell. The cell is the minimum unit of access.  The time it takes to fetch or store the contents of a cell is the same for all the cells in memory.  memory registers - Correct answer the two registers used to implement the fetch and store operations. Fetch and store operations require two operands, the address of the cell being accessed and either the value being stored by the store operation or the value returned by the fetch operation.  Memory Address Register (MAR) - Correct answer holds the address of the cell to be fetched or stored. Because the MAR must be capable of holding any address, it must be at least N bits wide, where 2^N is the address space of the computer.  Memory Data Register (MDR) - Correct answer contains the data value being fetched or stored. Typically a multiple of 8 bits, since it it is used to hold the data to be fetched or stored and all data must be stored in cells that are 8 bits wide.  method - Correct answer a sequence of statements that has a name, may have formal parameters, and may return a value. A method can be invoked any number of times, with different values for its parameters.  method signature - the name of a method and the type of its parameters  mutator method - Correct answer a method that changes the state of its objects, as opposed to an accessor method  object - Correct answer a value of a class type  object reference - Correct answer a value that denotes the location of an object in memory. In Java, a variable whose type is a class contains a reference to an object of this class.  object-oriented programming - Correct answer designing a program by discovering objects, their properties, and their relationships  parameter - Correct answer an item of information that is specified to a method when the method is called. For example, in the call System.out.println("Hello, World!"), the parameters are the implicit parameter System.out and the explicit parameter "Hello, World!".  parameter passing - Correct answer specifying expressions to be actual parameter values for a method when it is called.  primitive data type - Correct answer a data type structured by Java to hold a single data item (Integer, character, floating point, true/false, long)  pseudocode - Correct answer a high-level description of the actions of a program or algorithm, using a mixture of English and informal programming language syntax  Random Access Memory - Correct answer RAM, electronic circuits in a computer that can store code and data of running programs. random access is the ability to access any value directly without having to read the values preceding it.  register - Correct answer a storage cell that holds the operands of an arithmetic operation and that, when the operation is complete, holds its results.  scope - Correct answer the part of a program in which a variable is defined  software - Correct answer (computer science) written programs or procedures or rules and associated documentation pertaining to the operation of a computer system and that are stored in read/write memory  stored program concept - Correct answer central characteristic of Von Neumann Architecture and the design of all modern computers, in which the instructions to be executed by the computer are represented as binary values and stored in memory  syntax - Correct answer rules that define how to form instructions in a particular programming language  terabyte - Correct answer 1 trillion bytes - in binary actually 1099511627776, or 2^40 bytes  transistor - Correct answer the elementary building block of all modern computers. A solid-state device with no moving parts that can be in either an on or off state. Transistors, along with electrical conducting paths to them, are printed photographically on a wafer of silicon to produce an integrated circuit, or chip (currently about 1 billion transistors can be printed in a space of 1 sq cm)  truth table - Correct answer a mathematical table used to compute the functional values of logical expressions on each possible combination of their logical variables. Often the variables used are 0s and 1s but they may be Ts and Fs as well  Von Neumann architecture - Correct answer Theoretical model for nearly all modern computers. Such computers are composed of four major subsystems (memory, input/output, the ALU or arithmetic/logic unit, and the control unit), the stored program concept (in which the instructions to be executed by the computer are represented as binary values and stored in memory), and the sequential execution of instructions (in which one instruction at a time is fetched from memory and passed to the control unit, where it is decoded and executed).  white space - Correct answer any sequence of only space, tab, and newline characters