D

Data refers to the pieces of information that are operated on by programs. Originally, “data” was the plural of “datum”; however, the form “data” is now commonly used as both singular and plural.

A day number is an integer value representing the number of days between two dates.

A debugger is a program that controls the execution of another program so that you can see what the latter program is doing. You can download a debugger from the WWW that is compatible with the development environment on the CD in the back of this book.

Debugging is the art of finding and eradicating errors (bugs) from your program. One of the best ways of debugging a program is to try to explain it to someone else in great detail. If you don't see your error, the other person almost certainly will!

A dedicated register is a register such as the stack pointer whose usage is predefined rather than determined by the programmer, as in the case of general registers such as eax.

A default argument is a method of specifying a value for an argument to a function when the user of the function doesn't supply a value for that argument. The value of the default argument is specified in the declaration of the function.

A default constructor is a member function that is used to create an object when no initial value is specified for that object. For example, string::string() is the default constructor for the string class.

The default keyword is used with the switch statement to specify an action to be performed when none of the case statements match the selection expression of the switch.

The delete operator is used to free memory previously used for variables of the dynamic storage class. This allows the memory to be reused for other variables.

Derived class: see inheritance.

A destructor is a member function that cleans up when an object expires; for an object of the auto storage class, the destructor is called automatically at the end of the block where that object is defined.

A digit is one of the characters used in any positional numbering system to represent all numbers starting at 0 and ending at one less than the base of the numbering system. In the decimal system, there are ten digits, '0' through '9', and in the hexadecimal system, there are sixteen digits, '0' through 9 and 'a' through 'f'.

A double is a type of floating-point variable that can represent a range of positive and negative numbers, including fractional values. With most current C++ compilers, including the one on the CD in the back of the book, these numbers can vary from approximately 4.940656e – 324 to approximately 1.79769e + 308 (and 0), with approximately 16 digits of precision.

Dynamic memory allocation is the practice of assigning memory locations to variables during execution of the program by explicit request of the programmer.

Variables of the dynamic storage class are assigned memory addresses at the programmer's explicit request. This storage class is often used for variables whose size is not known until run time.

Dynamic type checking refers to checking the correct usage of variables of different types during execution of a program rather than during compilation; see type system for further discussion.

Dynamic typing means delaying the determination of the exact type of a variable until run time rather than fixing that type at compile time, as in static typing. Please note that dynamic typing is not the same as dynamic type checking; C++ has the former but not the latter. See type system for further discussion.