|
Introduction
Code 39 (also known as USS Code 39, Code three of nine) is the first alpha-numeric symbology developed to be used in non-retail environment. It is widely used to code alphanumeric information, such as the model number etc.
Code39 is designed to encode 26 upper case letters, 10 digits and 7 special characters:
A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
-, ., *, $, /, +, %, SPACE.
It Is called code 39 or three of nine because each character encoded is made up of 5 bars and 4 spaces for a total of 9 elements and 3 out of 9 element are always wide.
A complete code 39 barcode must include a start character * and a stop character *. In this way code 39 is self-checking.
The height of the bars must be at least 0.15 times of the symbol’s length or 0.25 inches, whichever is larger.
Code 39 is a discrete symbology. Two adjacent characters are separated by an inter-character gap. To have the good barcode quality, the width of the inter-character gap usually equals to the width of the narrowest element, called X.
Code39 requires a starting quiet zone with the minimum 10 times of X dimension or 0.10 inch whichever is greater. The same width requirement applies to the trailing quiet zone.
Variants
Code 39 Mod 43 – In applications that require very high level of accuracy a modulo 43 check sum digit is appended to the last character. Also known as HIBC and LOGMARS.
Code 39 Extended – this encoding variant allows the full ASCII table, 128 characters to be encoded.