Abstraction

Identifying the distinguishing characteristics of a class or object without having to process all the information about the class or object. When you create a class—for example, a set of table navigation buttons—you can use it as a single entity instead of keeping track of the individual components and how they interact.

Encapsulation

An object-oriented programming term for the ability to contain and hide information about an object, such as internal data structures and code. Encapsulation isolates the internal complexity of an object’s operation from the rest of the application. For example, when you set the Caption property on a command button, you don’t need to know how the string is stored.

Object-oriented programming (OOP)

A system of programming that permits an abstract, modular typing hierarchy, and features polymorphism, inheritance, and encapsulation.

Dynamic-link library (DLL)

A Windows term for a set of routines that can be called from procedures and are loaded and linked into your application at run time. DLLs include utility routines or specific functions not intrinsic to Microsoft Windows

Docked

For toolbars, fixed to the top, bottom, or side of a Visual FoxPro window. The Project Manager can be docked to the top of a Visual FoxPro window.

Drag and drop

A feature that enables you to drag one object onto another to perform an action. To drag an object, click the object and, while holding down the mouse button, move it to the new location. When you are satisfied with the location, release the mouse button to drop the object.

Element

In Visual FoxPro, one of the individual members that make up an array.

Embed

A term for inserting a copy of an object from one application into another. Once the copy is embedded, it has no further association with the object from which it was copied. If the original object changes, the embedded copy does not.

Equi-join

A join in which records from two tables are combined and added to the result set only when there are equal values in the joined fields. The inner and outer join types you use in query Design view are equi-joins. In SQL view, however, you can create joins that aren't equi-joins, but select records when the value in one join field is >, <, <>, >=, or <= the value in the other join field.

Escape sequence

A sequence of keystrokes or output characters that begins with the ESC character. Escape sequences are typically used for positioning the cursor and controlling the display of text on the screen, or as codes to control printers.

Event

An action, recognized by an object, for which you can write code to respond. Events can be generated by a user action–such as clicking the mouse or pressing a key–by program code, or by the system, as with timers.

Event code

Code that is executed when an event occurs. The code can also be called programmatically.

Event-driven programming

A programming model that emphasizes event code rather than the sequential code used in procedural programming.

Event loop

The interactive, run-time environment established by the READ EVENTS command and terminated by the CLEAR EVENTS command.

Executable program

Executable programs are created in the Professional Edition of Visual FoxPro with the Project Manager and have an .EXE file extension.

Execution plan

The order in which join and filter clauses are evaluated when a view or query is run.

Expression

Any combination of variables, operators, constants, functions, and names of fields, controls, and properties that evaluates to a single value. You can use expressions as settings for many properties, and to set criteria or define calculated fields in queries.

Field

Any data item contained in a record. One or more fields make up a record in a table, and one or more records make up a table.

Field-level rule

A validation rule associated with a field that is activated when the field value is inserted or changed, and most often used to verify data entry and correctness. Field-level rules are activated before record-level rules and triggers, and work during buffered updates. Contrast trigger.

File skeleton

A series of wildcards, such as? and *, that specify a particular file name structure to be looked for in a file search.

Filter

A set of criteria applied to records in order to show a subset of the records or to sort the records.

Flag

A variable whose value, true (. T.) or false (. F.), indicates whether some condition holds or whether some event has occurred. A flag is used to control the program’s actions at some later time.

Floating

Able to move freely as its own window. For example, the Visual FoxPro toolbars, and the Project Manager and its tabs, can all float.

Foreign key

A column, or combination of columns, whose values are required to match a primary key in another table. Used to join related tables.

Form

A container class. A collection of one or more pages that behaves like a standard window or dialog box. A form contains controls for displaying and editing data. Forms can be contained within a form set.

Form set

A container class. A collection of one or more related forms. Use the Form Designer to arrange forms within the form set.

Forward link

The path and file name information, stored in the database container (.DBC), that links the database to files for tables that reside in the database.

Foxhole

Equivalent to the average height and width of a character based on the current font of the form in which an object is contained. Foxels are useful when developing cross-platform applications for character-based and graphical platforms.

FoxPro link library (FLL)

A Visual FoxPro compatible version of a DLL created in C; extends the functionality of Visual FoxPro.

Free table

A table that is not contained in a database. A .DBF file created in a previous version of FoxPro is a free table until it is added to a database. Contrast database table.

FTP

File Transfer Protocol. A protocol that makes it possible for a user to transfer files from one location to another over the Internet.

URLs of files on FTP servers begin with ftp://.

Many Internet sites have established publicly accessible repositories of materials that can be obtained using FTP with the account name "anonymous." Thus, these sites are called "anonymous ftp servers." See also HTTP, URL, World Wide Web (WWW).

Function

A preprogrammed calculation that can be carried out on request from any point in a Visual FoxPro program. Because a function takes in one or more arguments and returns a single value, it can be embedded in an expression. Functions contain a pair of parentheses that distinguish them from commands. For example, ROW () is a function. Functions can be from Visual FoxPro or user-defined. See also argument, expression, user-defined function.

Gateway

A computer that provides a transfer point and protocol conversion between networked computers.

Generated code

Programs created by GENMENU, the Visual FoxPro menu generator. Generated menu programs have an .MPR extension.

Generated name

A unique name generated by SYS(2015). These names are inserted in generated programs with corresponding clauses and code.

Globally unique identifier (GUID)

An identifier used to precisely identify objects and interfaces. All Windows applications and OLE objects have a GUID that is stored in the Windows registry.

Grid

A control that creates a grid allowing you to present data in a tabular format. Grid controls contain column headers, columns, and column controls.

Group band

Fields that appears together in a report based on criteria that you specify by choosing Data Grouping from the Report menu.

Group footer

A report band in which objects can be defined to print each time a group expression changes. Group footers usually contain calculated values for data in the group.

Group header

A report band in which objects can be defined to print each time a group expression changes. Group headers usually contain information to preface the data that follows.

Handle

A number assigned to a window that is used by the operating system to keep track of the attributes of the window. In a C or C++ library, a handle is a pointer.

Hot spot

In a Help system, an area in a bitmap that is "hot," meaning that it reacts when you move the mouse cursor on this area. The mouse cursor changes to a hand symbol and, when you click the mouse button, the topic defined in the hotspot editor appears. In online Help, hot spots are usually buttons and words that are green.

HTML

Hypertext Markup Language, or HTML, is a system of marking up or tagging a document so that it can be published on the World Wide Web. Documents prepared in HTML include reference graphics and formatting tags. You use a Web browser (such as Microsoft Internet Explorer) to view these documents.

HTTP

Hypertext Transfer Protocol. The Internet protocol used by World Wide Web browsers and servers to exchange information. The protocol makes it possible for a user to use a client program to enter a URL (or click a hyperlink) and retrieve text, graphics, sound, and other digital information from a Web server. URLs of files on Web servers begin with http://. See also FTP, URL, World Wide Web (WWW).

In-process

A DLL component that runs in the same process address space as the client that calls it.

Independent .IDX

Index files containing one index entry. An independent index file cannot have the same name as the associated table and will not automatically open with the table.

Inheritance

An object-oriented programming term. The ability of a subclass to take on the characteristics of the class it’s based on. If the characteristics of the parent class change, the subclass on which it is based inherits those characteristics. For example, if you add a new property, IsBold, to an editing control, any subclasses based on your control will also have an IsBold property.

Inner join

A join in which records from two tables are combined and added to a query's results only if the values of the joined fields meet a specified condition. For example, the default join between tables in query Design view is an inner join that selects records from both tables only when the values of the joined fields are equal.

Input mask

A property of fields and controls that restricts or dictates the format of user input. For example, an input mask such as (###) ###-#### restricts input to North American phone number format.

Instance

An object-oriented programming term. An object created from a class definition. Unlike a class, which is just a definition, an instance actually exists as an object that can be used to perform tasks. For example, a text box on a running form is an instance of the TextBox class.

International characters

Characters, such as é, that include diacritical marks and therefore allow data manipulation in languages other than English.

IP address

Four numbers, separated by periods, that represent the internet name and location of a network device.

ISAPI

Internet Server Application Programming Interface. A set of functions for Internet servers, such as a Windows NT Server running Microsoft Internet Information Server (MIIS).

Join