Barcodes

• Barcode


  A means of representing data in a machine-readable form
• Traditional barcodes


  • Represent data by using a set of parallel lines of varied width and spacing
  • Each character in a barcode is represented by seven equal-sized bars
  • Bars are coloured in either black or white (sometimes a different secondary colour is used) to represent the characters in the code
• Check digit


  An extra digit or character added to the end of a long code, computed by applying an algorithm to the other digits
• Barcode validation


  1. Check digit is calculated and compared to the check digit at the end of the code

  2. If it doesn't match, there must have been an input error

  3. Validation can be carried out by software embedded within the barcode reader
• The code is usually printed below the barcode in case the barcode cannot be read, allowing the code to be entered manually
• Most barcode readers indicate that the barcode has been read successfully, for example by sounding a beep or showing a green light.
• Barcode readers are very common; the technology is reliable and well understood. Laser scanners, such as those that you might find in a supermarket, are the most common type of barcode reader. Laser scanners can be small wired or wireless handheld devices, or larger fixed units. Consumer devices, such as those found at self-service checkouts, will usually have multiple lasers so that they are easier to use.
• QR codes are typically used to provide a link to a particular page on a website, or to provide a link to an email or app that holds, for example, purchase details for concert tickets or travel information such as train times and seat numbers for a journey. 'QR' stands for 'quick response'.
• A QR code can store up to 7,089 numbers or 4,296 characters. Because of the higher storage capacity, some businesses are using QR codes to replace barcodes in their business systems.
• QR code scanners do not use lasers; the codes are captured and read by taking an image of the QR code, either with a dedicated scanner, or by using a camera and app on a mobile device.
• To read the code, a light from a laser illuminates the barcode. More light is reflected from the white areas than from the black bars. The reflected light is captured by one or more photoelectric cells that generate a set of electrical pulses that correspond to the black and white stripes in the barcode. These pulses are processed and converted to a binary number that represents the code.