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An element is one of the variables that make up a vector or an array.

The keyword else causes its controlled block to be executed if the condition in its matching if statement turns out to be false at run time.

An empty stack is a stack that currently contains no values.

Encapsulation means hiding the details of a class inside the implementation of that class rather than exposing them in the interface. This is one of the primary organizing principles of object-oriented programming.

An end user is the person who actually uses an application program to perform some useful or interesting task. Also see application programmer, library designer.

The ENTER key is the key that generates a newline character, which tells an input routine that the user has finished entering data.

Envelope class; see manager/worker idiom.

An enum is a way to define a number of unchangeable values, which are quite similar to consts. The value of each successive name in an enum is automatically incremented from the value of the previous name (if you don't specify another value explicitly). The term enum is short for “enumeration”, which is a list of named items.

An exception is an interruption in the normal flow of control in a program. When a function encounters an error condition, it can “throw an exception” to notify any calling function that wishes to handle this problem that it has occurred. If none of the calling functions handles the exception via a catch statement, the program will terminate.

Executable; see executable program.

An executable program is a program in a form suitable for running on a computer; it is composed of machine instructions along with data needed by those instructions.

The explicit keyword tells the compiler not to call a specified constructor unless that constructor has been called explicitly. This prevents such a constructor from being called to perform an implicit conversion.