| Analog-to-Digital Converter | Device in a scanner that converts analog shades and intensity of colors into numerical values for use in a computer. Also known as ADC or A/D Converter. |
| A: | Driver letter designation most commonly given with the main floppy disk drive in a computer. |
| A3 | Paper size for documents measuring up 11.7" x 17". |
| A4 | Paper size for documents measuring up to 8.27" x 11.69". |
| A5 | Paper size for documents measuring up to 5.83" x 8.28". |
| Acquire | Command used to open the TWAIN interface in most image editing programs. Usually found in the File menu. |
| Additive Primaries | Red, green and blue light combined to make white light. All other colors can be made from various combined amounts of red, green and blue light. In computers, red, green and blue are used to create the colors available in the 24-bit true color palette. |
| Acrobat Reader | Application by Adobe Systems, Inc., used for viewing PDF (portable document format) files. PDF files are electronic versions of manuals and other documents that include fonts and illustrations. They can be read on-screen or printed out. |
| Aliasing | Jagged edges in images caused by sharp contrast between the adjacent pixels. |
| America Online | Popular on-line service offering chat rooms, e-mail and internet connections. |
| Anti-aliasing | Technique in imaging programs used to blend hard-edged objects together with the background to prevent aliasing. |
| Apple Menu | On a Macintosh, the menu in the upper-left corner of the designated by an icon resembling Apple’s rainbow-striped apple logo. The Apple Menu is where common tasks are located. |
| Apple System Profiler | System tool on Macintosh computers using System Software 7.6 or up. The Apple System Profiler shows system components and device status. |
| Application Software | Computer programs designed to aid in a task, such as image editing, optical character recognition or word processing. |
| Artifact | An unwanted visual anomaly or defect that degrades image quality. |
| ASCII | Acronym for American Standard Code for Information Interchange. A standard computer language that assigns a numerical code value to characters, symbols and numbers. Can be used between computer programs and platforms. |
| ATM | Acronym for Adobe Type Manager. Adobe Systems, Inc. program for improving the display of fonts at any size on a monitor. |
| Attachment | A file sent along with an e-mail message. |
| AVI | Acronym for Audio Video Interleaved. Multimedia file format for sound and moving pictures. Files saved in this format have ".avi" as a file extension. |
