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Cursor (computers)
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In computing, a cursor is an indicator used to show the position on a computer monitor or other display device that will respond to input from a text input or pointing device. The text cursor may be referred to as a caret in some cases. This term came about from older unix systems that used the caret symbol as a text insertion indicator .
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Encyclopedia
In computing, a cursor is an indicator used to show the position on a computer monitor or other display device that will respond to input from a text input or pointing device. The text cursor may be referred to as a caret in some cases. This term came about from older unix systems that used the caret symbol as a text insertion indicator . The mouse cursor may be referred to as a mouse pointer , owing to its arrow shape on some systems.
Text cursor
In most command line interfaces or text editors, the cursor 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 the old days of 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. Some older graphical user interfaces such as OPEN LOOK used a caret-shaped insertion marker. Still today, the text cursor is sometimes called caret.
Some interfaces use an underscore or thin vertical bar to indicate that the user is in insert 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.
Bidirectional 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.
Mouse cursor
Interfaces driven by a computer mouse or other pointing device add a second cursor to show the current position of the mouse pointer. Douglas Engelbart's On-Line System originally referred to the cursor as a "bug" or "tracking spot" . In the On-Line System, the cursor appearance alternated "between the characters uparrow and plus" . On modern systems the default mouse cursor is a badly-drawn, crooked arrow pointing up and to the left, and is called the "mouse pointer".
In text user interfaces, including the Linux console and many MS-DOS programs, this cursor is frequently a solid rectangle; depending on the interface, the rectangle may always be a single color, or may be the opposite color of whatever lies "below" it. Graphical user interfaces usually use an arrow-like pointer to show the mouse position, and a solid line as a text insertion point.
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. Many TUIs and GUIs give the user the option to turn off the mouse cursor when text is being typed.
In many GUIs, the mouse cursor changes shape depending on the circumstances. For example:
- In text that the user can select or edit, the cursor changes to a vertical bar with little cross-bars (or curved serif-like extensions) at the top and bottom — sometimes called an "I-beam" since it resembles the cross-section of the construction detail of the same name.
- When displaying a document, the cursor can appear as a hand with all fingers extended allowing scrolling by "pushing" the displayed page around.
- Graphics-editing cursors such as brushes, pencils or paint buckets may display when the user edits an image.
- On an edge or corner of a window the cursor usually changes into a double arrow (horizontal, vertical, or diagonal) indicating that the user can drag the edge/corner in an indicated direction in order to adjust the size and shape of the window.
- While a computer process is performing tasks and cannot accept user input, a wait cursor (an hourglass in Windows before Vista and many other systems, spinning ring in Windows Vista, watch in classic Mac OS, or spinning ball in Mac OS X) is displayed when the mouse cursor is in the corresponding window.
- When the cursor hovers over a hyperlink, it changes into a hand with an outstretched index finger. Often some informative text about the link may pop up in a tooltip, which disappears when the user moves the cursor away. The tooltips revealed in the box depend on the implementation of the web browser; many web browsers will display the "title" of the element, the "alt" attribute, or the non-standard "tooltips" attribute. This cursor shape was first used for hyperlinks in Apple Computer's HyperCard.
The mouse cursor hotspot is the mouse cursor's pixel used to click. A hotspot is normally along the cursor edges or in its center, though it may reside at any location in the cursor icon.
See also
- Susan Kare, designer of several of the common cursor shapes
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