How does a camera know that its taking a portrait or landscape computer?

Because, say if you are taking a picture in, no mater how you rotate it, how does the camera know you are taking a portrait picture?

The camera puts a tag on each image file that tells it when the camera is in the vertical or horizontal position.

Some cameras have this as an option ... you usually have to turn it on.

In most newer digital cameras there is a small single axis sensor to detect which way the camera is rotated, vertical or horizontal. This information is stored in the EXIF data for the picture, and when you open it on your computer, it automatically rotates the picture.