Cursor
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A cursor is a movable marker that indicates a position. The term has been used with this meaning since the 16th century, for a wide variety of movable position markers.
Slide_rule_cursor.jpg
On slide rules, a cursor is a sliding glass or plastic plate that has a fine line etched or painted onto it to line up the different scales. Slide rule operation consists of finding a number on one scale and lining it up with a number on another scale. If the scales are separated by any distance, the cursor is used to accurately line them up or read values.
On a typewriter, the cursor indicates the position at which the next key to be struck will type.
The term is now most commonly used as a feature of a computer user interface. On CRT character-based interfaces, the cursor was originally (and is still sometimes) a solid rectangle indicating the position of the next character to be typed or the next to be deleted when backspacing or overtyping. On modern computers with a graphical user interface, there are two cursors:
- the mouse pointer, usually an arrow, that moves on the screen as you move the computer mouse or other pointing device.
- an insertion point, displayed when editing text to show the location of any future modifications. This is usually represented by a blinking vertical line.
In many computer programs, the shape of the mouse pointer cursor changes when the user's task changes or when it is over a different window. For instance:
- In text that can be selected, the cursor can change to a vertical bar with little cross bars at the top and bottom.
- In move mode (for moving an image or icon), the cursor is a hand with all fingers stretched.
- A graphics-editing cursor is displayed while the user is editing an image.
- On an edge of a window the cursor changes into a double arrow (horizontal, vertical, or diagonal) indicating that the edge can adjusted in the indicated direction.
- When a computer process is performing tasks and is unable to accept user input, a wait cursor (an hourglass or watch) is sometimes displayed in the corresponding window.
- When the cursor hovers over a hyperlink, it changes into a hand with a stretched index finger. Also often some informative text about the link pops up, not in a regular window, but in a special hovering box, which disappears when the cursor is moved away. The "Tool Tips" revealed in the box are dependent on the implementation of the web browser; many web browsers will display the "title" of the element, the "alt" attribute, or the non-W3C- standard "tooltips" attribute.
In database packages, cursor refers to a control structure for the traversal of records returned by a query.