In computing, a scanner is a device that analyzes images, printed text, or handwriting, or an object (such as an ornament) and converts it to a digital image. Most scanners today are variations of the desktop (or flatbed) scanner. The flatbed scanner is the most common in offices. Hand-held scanners, where the device is moved by hand, were briefly popular but are now not used due to the difficulty of obtaining a high-quality image. Both these types of scanners use charge-coupled device (CCD) or Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor.