Cursor (user interface)

In computer user interfaces, a cursor is an indicator used to show the current position for user interaction on a computer monitor or other display device that will respond to input from a text input or pointing device. The mouse cursor is also called a pointer, owing to its resemblance in usage to a pointing stick.
Origin of the term.
"Cursor" is Latin for 'runner.' A cursor is the name given to the transparent slide engraved with a hairline that is used for marking a point on a slide rule. The term was then transferred to computers through analogy.
Text cursor.
In most command-line interfaces or text editors, the text cursor, also known as a caret, is an underscore, a solid rectangle, or a vertical line, which may be flashing or steady, indicating where text will be placed when entered (the insertion point). In text mode displays, it was not possible to show a vertical bar between characters to show where the new text would be inserted, so an underscore or block cursor was used instead. In situations where a block was used, the block was usually created by inverting the pixels of the character using the boolean math exclusive or function. On text editors and word processors of modern design on bitmapped displays, the vertical bar is typically used instead.
In a typical text editing application, the cursor can be moved by pressing various keys. These include the four arrow keys, the Page Up and Page Down keys, the Home key, the End key, and various key combinations involving a modifier key such as the Control key. The position of the cursor also may be changed by moving the mouse pointer to a different location in the document and clicking.
The blinking of the text cursor is usually temporarily suspended when it is being moved; otherwise, the cursor may change position when it is not visible, making its location difficult to follow.
Some interfaces use an underscore or thin vertical bar to indicate that the user is in insert mode, a mode where text will be inserted in the middle of the existing text, and a larger block to indicate that the user is in overtype mode, where inserted text will overwrite existing text. In this way, a block cursor may be seen as a piece of selected text one character wide, since typing will replace the text "in" the cursor with the new text.
Bi-directional text.
A vertical line text cursor with a small left-pointing or right-pointing appendage are for indicating the direction of text flow on systems that support bi-directional text, and is thus usually known among programmers as a 'bidi cursor'. In some cases, the cursor may split into two parts, each indicating where left-to-right and right-to-left text would be inserted.
Pointer.
In computing, a pointer or mouse cursor (as part of a personal computer WIMP style of interaction) is a symbol or graphical image on the computer monitor or other display device that echoes movements of the pointing device, commonly a mouse, touchpad, or stylus pen. It signals the point where actions of the user take place. It can be used in text-based or graphical user interfaces to select and move other elements. It is distinct from the cursor, which responds to keyboard input. The cursor may also be repositioned using the pointer.
The pointer commonly appears as an angled arrow (angled because historically that improved appearance on low resolution screens), but it can vary within different programs or operating systems. The use of a pointer is employed when the input method, or pointing device, is a device that can move fluidly across a screen and select or highlight objects on the screen. In GUIs where the input method relies on hard keys, such as the five-way key on many mobile phones, there is no pointer employed, and instead the GUI relies on a clear focus state.
The pointer or mouse cursor echoes movements of the pointing device, commonly a mouse, touchpad or trackball.
This kind of cursor is used to manipulate elements of graphical user interfaces such as menus, buttons, scrollbars or any other widget. It may be called a "mouse pointer", because the mouse is the dominant type of pointing device used with desktop computers.
Appearance.
The pointer "hotspot" is the active pixel of the pointer, used to target a click or drag. The hotspot is normally along the pointer edges or in its center, though it may reside at any location in the pointer.
In many GUIs, moving the pointer around the screen may reveal other screen hotspots as the pointer changes shape depending on the circumstances. For example:
I-beam pointer.
The I-beam pointer (also called the I-cursor) is a cursor shaped like a serifed capital letter "I". The purpose of this cursor is to indicate that the text beneath the cursor can be highlighted, and sometimes inserted or changed.
Pointer trails and animation.
 can be used to enhance its visibility during movement. Pointer trails are a feature of GUI operating systems to enhance the visibility of the pointer. Although disabled by default, pointer trails have been an option in every version of Microsoft Windows since Windows 3.1x.
When pointer trails are active and the mouse or stylus is moved, the system waits a moment before removing the pointer image from the old location on the screen. A copy of the pointer persists at every point that the pointer has visited in that moment, resulting in a snake-like trail of pointer icons that follow the actual pointer. When the user stops moving the mouse or removes the stylus from the screen, the trails disappear and the pointer returns to normal.
Pointer trails have been provided as a feature mainly for users with poor vision and for screens where low visibility may become an issue, such as LCD screens in bright sunlight.
In Windows, pointer trails may be enabled in the Control Panel, usually under the Mouse applet.
Introduced with Windows NT, an "animated pointer" was a small looping animation that was played at the location of the pointer. This is used, for example, to provide a visual cue that the computer is busy with a task. After their introduction, many animated pointers became available for download from third party suppliers. Unfortunately, animated pointers are not without their problems. In addition to imposing a small additional load on the CPU, the animated pointer routines did introduce a security vulnerability. A client-side exploit known as the "Windows Animated Cursor Remote Code Execution Vulnerability" used a buffer overflow vulnerability to load malicious code via the animated cursor load routine of Windows.
Editor.
A pointer editor is software for creating and editing static or animated mouse pointers. Pointer editors usually support both static and animated mouse cursors, but there are exceptions. An animated cursor is a sequence of static cursors representing individual frames of an animation. A pointer editor should be able to:
Pointer editors are occasionally combined with icon editors, because computer icons and cursors share similar properties. Both contain small raster images and the file format used to store icons and static cursors in Microsoft Windows is similar.
Despite the similarities, pointer editors differ from icon editors in a number of ways. While icons contain multiple images with different sizes and color depths, static cursors (for Windows) only contain a single image. Pointer editors must provide means to set the hot spot. Animated pointer editors additionally must be able to handle animations.
3D cursor.
The idea of a cursor being used as a marker or insertion point for new data or transformations, such as rotation, can be extended to a 3D modeling environment. Blender, for instance, uses a 3D cursor to determine where future operations are to take place.