Direct :: Computer Science

Direct Direct input methods. In this report I am going to explain the different direct input methods starting off with bar codes. A single barcode number is actually seven units. A unit is either black or white. A unit that is black would display as a "bar". A unit that is white would display as a "space". Another way of writing a barcode unit is "1" for a single unit "black bar" and "0" for a single unit "white space". For instance, the number "1" is composed of the seven units, "0011001" or "space-space-bar-bar-space-space-bar". Remember, a single barcode number requires seven units. Also, on a UPC barcode the same numbers on the left-hand side (the Manufacturer Code) is coded different than the numbers on the right-hand side (Product Code). The left side numbers are actually the "inverted" or "mirrored" codes of the right side numbers, for instance what is a "bar" on the right-side, is a "space" on the left-side. The right-side codes are called "even parity" codes because there is an even number of "black bar" units. For instance the right-side "6" is "101000" - 2 even-numbered "black bar" units. The left-side is called "odd-parity" because there is an odd number of "black bar" units. For instance, the left-side "6" is "0101111" - 5 odd-numbered "black bar" units. Having different coded numbers for each side allows the barcode to be scanned in either direction. Direct input methods. In the second part of my report on direct input methods I am going to be talking about magnetic stripe readers. A magnetic stripe reader, also called a magstripe reader, is a hardware device that reads the information encoded in the magnetic stripe located on the back of a plastic badge. Magnetic stripe readers can be read by a computer program through a serial port, USB connection, or keyboard wedge, and are generally categorized by the way they read a badge. For instance, insertion readers require that the badge be inserted into the reader and then pulled out. Swipe readers require that the badge pass completely through the reader. The magnetic stripe on the back of a badge is composed of iron-based magnetic particles encased in plastic-like tape. Each magnetic particle in the stripe is a tiny bar magnet about 20-millionths of an inch long. When all the bar magnets are polarized in the same direction, the magnetic stripe is blank. Information is written on the stripe by magnetizing the tiny bars in either a north or south pole direction with a special electromagnetic writer, called an encoder. The writing process, called flux reversal, causes a change in the magnetic field that can be detected by the magnetic stripe reader.