Code 128 is a continuous, multi-level, full ASCII code. Each of the Code 128 characters consists of three bars and three spaces. The bars and spaces may be one, two, three, or four modules wide. The total length of each code 128 character is eleven modules, with the total length of the bar modules odd, and the total length of the space modules even.
Barcode 128 has three different encoding methods: A, B and C. The encoding is determined by the start code. The default encoding method is B and it is used for upper and lower case alpha. A is used for upper case alpha and control characters, and C is used for digits, encoding 2 digits per barcode character. You can specify a different encoding method (either at the start and/or in the middle of the data) by using a special data character. eFORMz uses the exclamation mark to specify special data characters. The sequences for special data characters are:
“!A” – to specify or switch to CODE A
“!B” – to specify or switch to CODE B
“!C” – to specify or switch to CODE C
“!S” – To switch the next data character of CODE B if currently using CODE A, or to switch the next data character to CODE A if currently using CODE B.
There are also 4 different function codes that various organizations use to delimit fields within barcodes They are FNC 1, FNC 2, FNC 3, and FNC 4. The sequences for these are “!1”, !2”, “!3”, and “4”, respectively.
“[Start_C]FNC19611804173422370101951” should be
“[Start_C]FNC142013326” should be
For a list of Code 128 characters, visit: http://www.adams1.com/128table.html
The final size of the barcode depends on the dimension of the smallest bar, the type of barcode, and the number of characters encoded. This website has a handy calculator to figure the total width: http://www.adams1.com/128code.html