Barcode DLL allows encoding all 256 characters as well as 4 special symbol characters: FNC1, FNC2, FNC3and FNC4.

Internally Code128 defines 3 character sets (A, B and C) to allow efficient encoding. Each character set contains 103 characters (including special symbol characters). A code128 symbol starts with one character set and latches to a different set with a latch codeword. Since these three character sets overlap, it is possible to get different barcodes with the same data encoded.

To allow space efficiency, during the encoding process, Barcode DLL selects the proper character sets and inserts necessary shift characters to make the symbol generated as short as possible.

Code128 requires a checksum character to ensure the data integrity. The checksum character has no meaning to the end user. Barcode DLL does not transmit the checksum digit back to the human readable text.

Under some circumstances it is necessary to represent some characters with an ASCII-only format. This kind of representation format is called escape sequence. For example, the four special Code128 symbol characters, FNC1~FNC4, do not have corresponding ASCII values. Consequently the only way to enter them into the Message property is through their escaped forms. Some applications and programming environments may only accept printable ASCII characters, and control characters must be escaped.

Tilde code sequence is the only escape method supported in Barcode DLL version 3.2 and above. The special character input method (escaping a character using a back-slash character followed by 3-digit character value) present in previous versions is now deprecated.

The tilde code consequences used in Code128 are listed as below:

UCC/EAN-128^[3] encodes structured data proposed by various industry standard bodies and authorized by GS1 organization. Each data type is identified with a numeric value, called Application Identifier (AI). Multiple AIs and values can be concatenated together into one barcode, such as:

(01)19421123450011(15)991231(10)101234

The data above contains multiple AIs and values:

The AI value determines the meaning and the length of the value part. Many of them encode a predefined length of data. For example, the SCC14 requires exact 14 digits and the Sell By Date requires exact 6 digits in YYMMDD format.

When the data length can be derived from AI, it is not necessary to add field separator (FNC1) in the barcode to separate two adjacent fields. However, if the first field has a variable data length, such a field separator is required. And in many applications it is often desirable to have a field separator between two fixed-length fields. The Code128 symbol character FNC1 serves this purpose.

To understand each data field, Barcode DLL requires you to enter the data in a special format. The AI must be enclosed with parentheses. From the AI Barcode DLL knows whether a field has a fixed length or a variable length. For all variable-length fields, Barcode DLL inserts field separator unless it ends the input.

Barcode DLL also performs data validation on the AI and the data, if the AI is known to the program.

If the AI is not listed in the table above ^[5], Barcode DLL can not know whether its data length is fixed or variable. Thus, Barcode DLL treats the data as if its data length is variable and inserts a field separator FNC1 when this field does not end the symbol.

For example, suppose that you set Message to (01) 19421123450011(8019)123456(15)051210. Barcode DLL understands that 01 AI requires fixed-length 14 digits data and AI 15 requires fixed-length 14 digits data. However, Barcode DLL does not understand AI 8019 and treats this field as if it has a variable length. Barcode DLL inserts a field separator at the end of this field (before AI 15).

Assuming that AI 8019 requires a fixed data length, you can tell Barcode DLL that the field has a fixed data length by appending a tilde character ~ at the end of the field. For example, you can assign the value below:

(01)94211234500122(8019)123456~(15)051210

When Barcode DLL sees the ~, it treats the current field as fixed-length.

On the other side, if a known AI has a fixed data length but you'd like to have a field separator at the end of the field, you can do so by adding an exclamation character at the end of field, such as:

(01)94211234500122!(8019)123456(15)051210

It forces a field separator to appear after the SCC14 number even AI 01 has a fixed data length and the field separator is not required. Sometimes this field separator is desirable because it is easier for the application to parse the input.

See the table below for the comparison among results produced by different inputs. The[ GS] is the scanner output for FNC1 character.

Barcode	Data input/Scanner output
	(01)94211234500122(8019)123456~(15)051210 0194211234500122801912345615051210
	(01)94211234500122!(8019)123456(15)051210 0194211234500122[ GS]8019123456[ GS]15051210
	(01)94211234500122(8019)123456(15)051210 01942112345001228019123456[ GS]15051210

Before version 3.4, Barcode DLL calculates mod10 check digits on SCC-14 and SSCC-18 numbers, but only When the property UccEanOptionalCheckDigit is TRUE. This behavior has been changed since version 3.4. Now the program calculates mod 10 check digit automatically, regardless the value of UccEanOptionalCheckDigit. This renders this property useless.

Barcode DLL performs check digit calculation on those AIs: 00, 01, 02, 410, 411, 412, 413, 414, 415, and 8018.

To create the barcode correctly you must enclose the AI with parentheses ( ). Barcode DLL only accepts numeric AI values. It reports an error when encountering a non-numeric character in the AI part. If AI does not appear in the known list (see the table above), and you do not want the data treated as variable length, you should tell so by appending a tilde character at the end of the field.

Sometimes, it is desirable to have the data separated by spaces in the human readable text. For example, you may like to see the human readable text (8101) 0 54321 1200(21)123456 instead of (8101)0543211200(21)123456. You can create the desirable human readable text by entering the message exactly like the one you'd like the human readable to be. Barcode DLL ignores the spaces during the encoding, but preserves them in the human readable text, as the one below illustrates:

Barcode DLL performs the following validations during the encoding process:

If your application does not pass the validation, you can not use UCC/EAN-128 to encode the data. Nevertheless, since UCC/EAN-128 encoding is based on Code128 symbology, you can encode the data directly with Code128. Here are several hints you may consider when converting the EAN-128 data into a Code128 input:

For example, Code128 with message ~18101054321120021123456 produces the exact barcode as the one using UCC/EAN-128 with message (8101)0 54321 1200(21)123456.

Some non-standard applications do not encode the FNC1 at the starting message. When this is the case, remove ~1 at the beginning of the input.

GTIN is the acronym for Global Trade Item Number, a 14-digit number that identifies trade items developed by GS1 organization. This number have many names, such as SCC-14 (Serial Container Code), UCC-14.

GTIN can be derived from UPC-A or EAN-13 numbers. The first digit is package indicator. Digit '0' and '9' have special meanings here - '0' often means that there is one item in the box, and '9' indicates a variable measure item. The package indicator is followed by GS1 company prefix (assigned by GS1) and item number (assigned by the company). They should be in total of 12 digits. This portion is the same as the first 12 digits in an EAN-13 number, or '0' plus the first 11 digits in a UPC-A number. The last digit is checksum, which is calculated based on Mod10 algorithm on previous 13 digits.

Because UPC-A and EAN-13 numbers can be thought as special cases of GTINs (the package indicator is '0'), a 14-digit GTIN unqiuely identifies any trade item (a single item or a container).

GTIN is often depicted using Interleaved 2 of 5 or GS1-128 symbologies. This is expected to change as GS1 is endorsing DataBar. The benefits of using DataBar is that it produces more compact barcodes, espcially when comparing with UPC-A and EAN-13 symbols. Furthermore, DataBar Expanded allows additional information to be encoded, such as serial number, weight or price.

DataBar Truncated and DataBar Stacked symbols have their height fixed to its X-dimension. That is, you can not change the height by modifying BarHeight property. They are always 13X.

In DataBar Stacked Omnidirectional and DataBar Expanded Stacked symbols, the overall size of the barcode (excluding human readable text and other elements) is not the same as BarHeight, because multiple rows exist.

To achieve omnidirectional scannability and standard conformance, the following minimum height should be observed for DataBar-14, DataBar Stacked Omnidirectional, and DataBar Expanded (X=NarrowBarWidth):

The widths of stacked symbols (DataBar Stacked etc.) can be very small to hold the human readable text in one line. When this happens, the human readable text will wrap into multiple lines. If this is not desired, turn the human readable text off and set it to the comment. You can set comment margin properties CommentMarginLeft and CommentMarginRight to adjust the with of comment block.

Normal (comment off, human readable on)	human readable off, comment on, CommentMarginLeft=200 mils

DataBar Expanded and DataBar Expanded Stacked usually encode a GTIN number plus additional information, such as price, weight, expiration date and so on. Moreover, any GS1-128 data can be encoded in DataBar Expanded and DataBar Expanded Stacked.

Although they are referred separately, DataBar Expanded Stacked is a superset of DataBar Expanded. Any DataBar Expanded symbols are also DataBar Expanded Stacked symbols. Therefore, in our implementation we use DataBar Expanded for both cases, you create DataBar Expanded Stacked symbols by setting symbols per row value to a non-zero value.

Because the support for DataBar Expanded is added in version 3.4, and we did not want to add additonal properties to break backward compatiblity, we choose an existing property, PDFMaxCols for this purpose. By default, PDFMaxCols is set to zero, which creates a non-stacked DataBar Expanded barcode. To create a DataBar Expanded Stacked barcode, set this property to an even number between 2 and 22. ^[7]

In PDF417 the security level is selectable. You can specify a value between 0 and 9 for PDF417SecurityLevel. Value 9 means automatic and the program selects the security level based on the data encoded and the recommendation from the PDF417 specification.

There are several properties determining the size and the shape of the symbol. PDFMaxRows sets the maximum number of rows allowable and PDFMaxCols sets the maximum number of columns. A PDF417 symbol can have 30 columns and 60 rows. It should be pointed out that the row and column here really mean code words, instead of modules. The width of the representation of a code word is much longer than its height. Value 0 allows Barcode DLL to select the value based on the amount of the data and the aspect ratio.

The data capacity is directly linked to the number of columns and rows. Setting PDFMaxRows and PDFMaxcols to small values results smaller data capacity. When the program is unable to encode the data within the limits, an error is reported.

Other related properties include PDFModuleHeigth, PDFModuleWidth and PDFAspectRatio. The smallest unit in a PDF417 symbol is called a module. The PDDFModuleWidth and PDFModuleHeight reflect the height and width of the module respectively.

PDFAspectRatio impacts the shape of the final symbol. The PDFAspectRatio is defined as the ratio of the height to the overall width of the symbol. Barcode DLL locates the solution that close matches the specified value. Note: in many cases to match the aspect ratio Barcode DLL has to increase the overall symbol size. Smaller PDFAspectRatio value usually produces more compact symbols.

PDFAspectRatio=0.5 (default)	PDFAspectRatio=0.2	PDFAspectRatio=1.0

PDF417 is capable of encoding all characters with ASCII values between 0 and 255. Depending on programming environment you may need tilde codes to escape some characters.

When creating PDF417 barcodes you can use the following tilde codes:

In a relatively clean environment where label damage is not likely, the right column indicators can be omitted and the stop pattern can be reduced to one module bar. This truncation reduces the data overhead and saves some space at the cost of performance and robustness.

Figure 10.2. Truncated PDF417 Barcode

To produce truncated PDF417 symbols, set the property PDF417TruncatedSymbol to TRUE.

GLI was introduced to allow output data stream to have interpretations different from the default character set (ISO8859-1). Since version 3.2, Barcode DLL has been capable of encoding GLI values. A GLI can be any number between 0 and 999999. The tilde code sequence ~7nnnnnn is used to enter the ECI value. The tilde code sequence can appear at any places of the input, provided that exact 6 digits follows ~7. For example to start an interpretation 10, enter ~7000010.

Using Macro PDF417, large amount data are splitted into several file segments and encoded into individual symbols. To create Macro PDF417 symbols, you need to enter the control block information using ~2 tilde code sequence. A sample input looks like this:

12345678901234567890~2[3][LA-CONFIDENTIAL][6][fn:part2|ts:199044|ad:Justin Power|fs:110990]

Syntax

The tilde code sequence for Macro PDF417 control block information is as follows:

~2[SI][FID][TS][fn:string|...]

The ~2 must appear at the end of the message. The data after the control block is ignored. The first three fields are required. The last field is optional and can contain several additional sub-fields.

Segment Index (SI)

In Macro PDF417, each symbol represents a segment of the whole file. To rebuild the whole file, the segment must be constructed in proper order. The value of segment index is 0 based. For example, for a file divided into k segments, the segment index can be any number between 0 and k-1.

The value allowed for SI is between 0 and 99.

File ID (FID)

All symbols belong to the same group have the same file ID. The File ID can be any string, such as archive2. Although the standard does not set a limit on the length of the File ID, keep in mind that the control block reduces the overall symbol capacity.

Total Segments (TS)

The “total segments” field is required for every symbol in the group. It should remain constant among all symbols.

Optional Fields

Macro PDF417 defines several optional fields to encode additional file information such as file name, timestamp, file size and checksum. All these fields must be at the end of the control block. If more than two optional fields are present, they should be separated with vertical bars |. Within a field, a colon : divides the name part and value part.

The acceptable field names are listed below:

For example, [fn:archive1.zip|ts:20051231|sd:user@example.com|cs:9901234] encodes 4 optional fields: file name (archive1.zip), time stamp (20051231), sender (user@example.com) and checksum (9901234).

In version 3.2, several optional features are added to Barcode DLL:

Data Matrix defines 30 different sizes. Most sizes are square, and a couple of them are rectangle. Regardless the final shape, the “real estate” unit, called module, is always square.

The size id, number of row and columns as well as the data capacity are listed in the table below.

In Barcode DLL you use DataMatrixTargetSizeID property to set the size you desire. If the property is set to 0, Barcode DLL picks up the size that fits the data encoded.

Previous to version 3.2, when DataMatrixTargetSizeID is too small to encode the whole data, Barcode DLL automatically increases the overall size. This behavior has changed in version 3.2. Now the progrom reports an error instead.

If DataMatrixTargetSizeID is more than holding the data, extra padding characters are added to the barcode. It is sometimes desirable if you want to have all the symbols created have the same size at the same time the data encoded vary from symbol to symbol.

The property DataMatrixModuleSize determines both the width and height of the smallest unit - a module. By default it is 20 mils. Same as all other length properties, the real value depends on Measurement.

Data Matrix is capable of encoding all characters in a single-byte character set, plus some symbol-specific characters. Depending on the programming environment you may need tilde codes to escape some characters. When creating data matrix barcodes, you can use the following tilde codes:

Data Matrix provides a way of abbreviating two industry specific header and trailer in one symbol character. This feature exists to reduce the overall symbol size. They must appear at the beginning of the input. You can use ~5 and ~6 to escape them respectively.

ECI was introduced to allow output data stream to have different interpretations different from the default character set (ISO8859-1). Since version 3.2, Barcode DLL has been capable of encoding ECI values.

An ECI can be any number between 0 and 999999. The tilde code ~7nnnnnn is used to enter the ECI value. The tilde code sequence can appear at any places of the input, but there must be exact 6 digits following ~7. For example to start an interpretation of 10, enter ~7000010.

The structural append feature allows up to 16 symbols in a structure. A capable reader can either buffer the contents of each symbol until all symbols are read.

To encode structural append, you must supply there items for each symbol:

The tilde code sequence is expressed in the following format:

~2[SI][FID][TS]

For example, tilde code sequence ~1[1][126][6] indicates that the current symbol belongs to a group with file identification number as 126, and there are 6 symbols in total in this group.

The ~2 tilde code sequence must appear at the end of the input. All three fields are required and must be enclosed with square brackets ([ and ]) and must follow the tilde code ~2.

File ID (FID)

The File ID is a number remaining the constant among all symbols in a group. It uniquely identifies the symbol group. The value for this field should be between 1 and 64516.

Sequence Indicator (SI)

Sequence Indicator is the 1-based index number of the current symbol. In a group with total 10 symbols, the first symbol has the SI of 1 and the last has the SI of 10.

Total Number of Symbols

The Total Number of symbols indicates how many symbols in the group.

Barcode DLL implements the MaxiCode based on ISO/IEC 16023. This ISO standard defines three standard fields in the primary message portion. the standard does not define the data structure for the secondary message. UPS adds many fields in the secondary message portion; and because the limit of data capacity, UPS uses a compression algorithm to put the whole fields into the secondary message. Barcode DLL encodes the secondary message as is. To produce a UPS compliant symbol, you need to consult UPS documentation for those additional fields and the compression algorithm.

When the symbol is encoded under mode 2 and 3, MaxiCode properties such as MaxicodeClass, MaxicodeCountryCode, MaxicodeZipcode are used unless the message starts with a UPS carrier prefix (see below). When the symbol is encoded under other modes, these properties are not placed into the symbol.

The MaxiCode requires the printing equipment having at least 200 dpi in resolution. Rasterizing images with a lower resolution will not produce a quality barcode.

If the message start with the standard carrier prefix ([)>[RS][GS]01[GS]YY), the related properties (MaxiCodeClass, MaxicodeCountryCode and MaxicodeZipCode) will be ignored during the encoding process. The primary and secondary messages are retrieved as follows: The first nine data characters [)>[RS][GS]01[GS]YY are extracted to be encoded in the secondary message. The next three data elements, representing the postal code, country code and service class code respectively are extracted from the source data. The remaining string of data is then encoded in the secondary message after the header [)>[RS][GS]01[GS]YY (excluding three RS characters which separate the three data elements). For example, the message above will be broken into the Primary Message and Secondary Message like this:

When creating Maxicode symbols, you can use the following tilde codes:

ECI was introduced to allow output data stream to have different interpretations different from the default character set (ISO8859-1). Started from version 3.2, Barcode DLL is capable of encoding ECI values.

An ECI can be any number between 0 and 999999. The tilde code ~7nnnnnn is used to enter the ECI value. The tilde code sequence can appear at any places of the input, but there must be exact 6 digits following ~7. For example to start an interpretation 10, enter ~7000010.

The structural append feature allows up to 8 symbols in a structure. A capable reader can either buffer the contents of each symbol until all symbols are read.

To encode structural append, you must supply there items for each symbol:

The tilde code sequence is expressed in the following format:

~2[SI][TS]

For example, tilde code sequence ~1[1][6] indicates that the current symbol is the first symbol in a group with 6 symbols in total.

The ~2 tilde code sequence must appear at the end of the input. All three fields are required. They must be enclosed within a pair of square brackets [ ] and must follow the tilde code sequence ~2.