CS101 Glossary of Terms

This is a partial list of terms used in CS101. If you think an important term is missing, please let us know.
a mechanism for hiding detail

abstract data type (ADT)
an interface and its associated expected behavior, usually implemented as an object containing some data (the internal representation) and a set of methods implementing the interface

abstraction barrier (or interface)
a set of operations (or methods of an object) that is used to access and/or operate on the internal representation

a method for extracting information from an object

activation record
holds the information on the call stack that is needed for one procedure call

actual parameter
the values that are passed into a procedure or method

a location in memory; each data item is stored at a particular memory address

the idea of how to carry out a computation, may be implemented as a procedure

base case
the simplest case, usually the termination case for a recursive algorithm

binary search tree
a data structure with in which every node refers to a left subtree and a right subtree such that all values in the left subtree are smaller than the value in the node and all elements in the right subtree are greater than (or equal to) the value in the node. the top node is called the root. the nodes with no children (left and right subtrees empty) are called leaves.

the relation between a symbol and its value

black box
something that can be used without knowing how it works inside

call stack (or execution stack)
the part of memory containing the bindings of formal parameters to actual values for procedure calls

circular list
a linked list in which the rear item refers back to the head item

a definition of a type of object

compound data
a collection of data treated as a single unit; has a constructor, accessors, and an identifier

a method used to create a new object

safety plus liveness

information that is manipulated by a computation

data abstraction

a method for providing a natural, high-level semantics for (a collection of) data while supressing the details of the internal representation

data flow model
a model of computation in which each computational component is represented as a box whose arguments and results may be connected from and to other boxes

a mechanism for hiding and protecting information

a "place" in which expressions are evaluated, usually with an associated set of bindings

execution stack
(see call stack)

expression tree
a diagram showing the operators and operands of an expression

formal parameter
the parameters declared for a method or procedure, into which the actual parameter values will be copied

memory that had been allocated but is no longer reachable by a process

garbage collection
claiming unreachable storage for reuse

an area of memory from which space for dyanamic structures are allocated

infix notation
a notation in which operators appear between the operands, as in 3 + 5

instance variables
the variables holding the internal representation of an object

(see abstraction barrier)

internal representation
the data representation (stored in the instance variables) of an object

a repeated computation, usually performed on a range of values or on the elements of a data structure

linked list
a data structure consisting of a sequence of values linked together in memory by a chain of references

the program will eventually provide a result

a programming language construct that supports iteration (for example, a while loop)

loop invariant
a property of, or relationship among, the values of the loop variables such that the property is true both initially and after each iteration of the loop; together with the termination condition, a loop invariant is useful in demonstrating the correctness of a loop

a place in the computer where values are stored for later retreival

a way of thinking about object-oriented programming in which objects communicate by sending messages to each other (to invoke methods on them)

an operation that one may invoke on an object

the act of changing the values of variables or data structures

an abstraction that encapsulates data and knows how to operate on the data

the way values are passed to a method or procedure

treating objects of many types in a uniform way

an expression that evaluates to either true or false

prefix notation
a notation in which operators appear before the operands, as in add(3,5)

primitive data
data, such as numbers and symbols, that are built into the language

a description of an activity to be carried out (by a computer)

an activity (carried out by a computer)

programming language
a language used to write a procedure or other description of a computation

a data structure with first-in first-out behavior, supporting the operations enqueue (to insert) and dequeue (to remove)

a recasting of one problem as another (somewhat different) problem

a reduction of a problem to another (typically smaller) instance of the same problem

representation invariant
a property that holds true of the internal representation initially and after the completion of each method

the meaning of an expression

a data structure with last-in first-out behavior, supporting the operations push (to insert) and pop (to remove)

stored information (associated with a process)

a class that extends another class, possibly by adding new methods or overriding existing methods

substitution model
a model of computation in which expressions are successively replaced by their values until a final result is reached

a name used to denote a value

the notation used to express an idea

tail recursion
a form of recursion in which the result of the recursive call is the final answer; no combining is done on the result of the recursive call

termination condition
a predicate that becomes true when a computation ends

top-down refinement
a design technique in which a problem is described at a highly abstract level and then broken down into finer and finer details until all the pieces are filled in