Question

what are the types of input scanning devices

Answer 1

Flatbed Scanner: The Flatbed scanner is most common desktop scanner. It resembles the copy machine. In a Flatbed scanner, The item being scanned rests on a glass plate whicle the scanning head moves underneath it. It works like a copy machine except that it creates a file of the document rather than a paper copy.
Sheetfed Scanner: Personal sheetfed scanners have gained popylarity during the last few years. These devices are more like fax machines, because they move the page being scanned past the scanning head. The main difference between this type and a flatbed scanner is that the image sensor does not move but the document itself is pulled past the mounted image sensor.
Handheld Scanner: The handheld scanner is a scanning device where the scanning element is built inro a small handheld unit. The handheld unit is then waved or rolled over the item being scanned.

Answer 2

Flatbed Scanner : You place the image on top of the scanner. The scanner moves the light and sensor itself and scans the whole image automatically. Most flatbed scanners are A4 size.
Handheld Scanner : You must manually push the light/sensor along the image. Handheld scanners are usually 5 inches wide.