While printers made getting data out of your computer easy, computer scanners did the reverse. Before scanners, the only way to get a page of data into a computer was to retype it. Even the earliest scanners couldn't do much more than treat data as images. That was great for photographs, but not so helpful when it came to actually using the data. For that, they had to teach scanners to read. Once that was done, computer printers, scanners, and supplies became a vital part of every office.Images or OCR
The first scanners were essentially digital cameras. They took pictures of pages or photographs and that was it. It made life easier because you could easily reprint the page, but you couldn't do much to manipulate the information on the page. Image-based scans treat the whole page as a single unit, while optical character recognition, or OCR, makes it possible to read the data on the page and manipulate that electronically.Flatbed Scanners
The first scanners to see large-scale popularity were flatbed computer scanners. Looking much like a photocopier without the print element, these systems use a large sheet of glass as an imaging surface. Just put your paper face down on the glass, close the lid, and push the button. With the capacity for up to A4 or larger pages, as well as smaller images like photographs, they are among the most useful scanners.Photography
While most scanners work well enough with photographic prints, dedicated photo, slide, and film scanners are a must for photographic archivists. The advantage of these scanners is that they can handle transparency, which is difficult for standard scanners to deal with.Comparing Scanners
The most important factors to consider when comparing scanners of the same kind are resolution and connection. The higher the resolution, the sharper the image; the faster the connection, the faster the image can get from the scanner to your computer. USB 2.0 will work but USB 3.0 is a better choice provided your computer supports it.