IBM 4400 manual Code 39 Structure

Code 39

Code 39

The Code 39 structure is shown in Figure 14 and described below.

			OPTIONAL
			CHECK DIGIT
SR, SC
POSITION
		UPPER GUARD BAND
QUIET	START	DATA FIELD	STOP	QUIET
ZONE	CODE		CODE	ZONE

HEIGHT

LOWER GUARD BAND

OPTIONAL READABLE DATA FIELD

Figure 8. Code 39 Structure

Quiet Zone

Both ends of the bar code structure require blank quiet zones. The quiet zones must be at least 0.25 inches wide and completely blank to ensure accurate reading of the start/stop codes and to prevent adjacent bar codes from overlapping. Be sure to provide sufficient space on the form for the quiet zones.

Start/Stop Codes

The start/stop code is a unique character identifying the leading and trailing end of the bar code. The start/stop code is automatically produced with each bar code. The start/stop code structure permits bidirectional bar code scanning.

Data Field

The bar code symbol uses a series of varying width bars and spaces to represent standard alphanumeric characters. Each wide or narrow bar or space is one element; each character in the data field has nine elements. The structure is three wide elements (bars or spaces) out of the nine total elements which compose one character.

Readable Data

The optional readable data field provides a readable interpretation of the bar code data. It can be printed above or below the bar code symbol.

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