---
title: "CGDisplayUnitNumber(_:)"
framework: coregraphics
role: symbol
role_heading: Function
path: "coregraphics/cgdisplayunitnumber(_:)"
---

# CGDisplayUnitNumber(_:)

Returns the logical unit number of a display.

## Declaration

```swift
func CGDisplayUnitNumber(_ display: CGDirectDisplayID) -> UInt32
```

## Parameters

- `display`: The identifier of the display to be accessed.

## Return Value

Return Value A logical unit number for the specified display.

## Discussion

Discussion The logical unit number represents a particular node in the I/O Kit device tree associated with the display’s framebuffer. For a particular hardware configuration, this value will not change when the attached monitor is changed. The number will change, though, if the I/O Kit device tree changes, for example, when hardware is reconfigured, drivers are replaced, or significant changes occur to I/O Kit. Therefore keep in mind that this number may vary across login sessions. For more information about I/O Kit, see IOKit Fundamentals.

## See Also

### Functions

- [CGAcquireDisplayFadeReservation(_:_:)](coregraphics/cgacquiredisplayfadereservation(_:_:).md)
- [CGAssociateMouseAndMouseCursorPosition(_:)](coregraphics/cgassociatemouseandmousecursorposition(_:).md)
- [CGBeginDisplayConfiguration(_:)](coregraphics/cgbegindisplayconfiguration(_:).md)
- [CGCancelDisplayConfiguration(_:)](coregraphics/cgcanceldisplayconfiguration(_:).md)
- [CGCaptureAllDisplays()](coregraphics/cgcapturealldisplays().md)
- [CGCaptureAllDisplaysWithOptions(_:)](coregraphics/cgcapturealldisplayswithoptions(_:).md)
- [CGCompleteDisplayConfiguration(_:_:)](coregraphics/cgcompletedisplayconfiguration(_:_:).md)
- [CGConfigureDisplayFadeEffect(_:_:_:_:_:_:)](coregraphics/cgconfiguredisplayfadeeffect(_:_:_:_:_:_:).md)
- [CGConfigureDisplayMirrorOfDisplay(_:_:_:)](coregraphics/cgconfiguredisplaymirrorofdisplay(_:_:_:).md)
- [CGConfigureDisplayMode(_:_:_:)](coregraphics/cgconfiguredisplaymode(_:_:_:).md)
- [CGConfigureDisplayOrigin(_:_:_:_:)](coregraphics/cgconfiguredisplayorigin(_:_:_:_:).md)
- [CGConfigureDisplayStereoOperation(_:_:_:_:)](coregraphics/cgconfiguredisplaystereooperation(_:_:_:_:).md)
- [CGConfigureDisplayWithDisplayMode(_:_:_:_:)](coregraphics/cgconfiguredisplaywithdisplaymode(_:_:_:_:).md)
- [CGCursorIsDrawnInFramebuffer()](coregraphics/cgcursorisdrawninframebuffer().md)
- [CGCursorIsVisible()](coregraphics/cgcursorisvisible().md)