Chapter 35: Advantages - Alphanumeric Native |
Summary |
In the landscape of barcode symbologies, the ability to encode letters alongside numbers is not merely a convenience --- it is often a fundamental business requirement. This chapter examines the alphanumeric capability of Code 39, which distinguishes it from numeric-only symbologies such as Interleaved 2 of 5 and UPC. We will explore how this native support for the full uppercase alphabet and selected special characters shapes the adoption of Code 39 across diverse industries, from military logistics to healthcare, automotive manufacturing, and beyond. Through practical examples, we will demonstrate how the technical characteristics of Code 39 --- its self-checking property, variable length, and straightforward encoding structure --- align with the needs of applications where part numbers, asset identifiers, and tracking codes routinely mix letters and digits. The chapter concludes with a comprehensive summary that reinforces the enduring value of this alphanumeric capability in an era of increasingly complex identification requirements. |
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1. Introduction: The Alphanumeric Imperative |
Imagine you are managing a warehouse containing thousands of distinct components. Each component has a part number. Some part numbers look like '12345' --- purely numeric. But many others look like 'AB-789-X2' or 'MOTOR-ASSY-03' or 'PN-9842-REV-B'. These alphanumeric identifiers are the language of modern inventory management, engineering documentation, and supply chain logistics. They carry meaning: the letters indicate product families, origins, revisions, or categories. The numbers provide sequence or specification details. Together, they create an identifier that is both human-readable and information-rich. |
Now imagine you are tasked with implementing a barcode system to track these components. You survey the available barcode symbologies. You find that Interleaved 2 of 5, a popular choice for warehouse applications, can only encode numeric digits . You find that UPC, the ubiquitous retail code, is similarly numeric-only and fixed-length . These symbologies are excellent for their intended purposes --- high-density numeric encoding for point-of-sale and case-level tracking --- but they simply cannot represent your part numbers without forcing you to abandon the letters or devise a clumsy mapping scheme. |
This is precisely the problem that Code 39 was designed to solve. Introduced in 1974 by Intermec Corporation, Code 39 was the first barcode symbology capable of encoding the full alphanumeric character set --- uppercase A through Z, digits 0 through 9, and a selection of special characters . This chapter explores how this alphanumeric native capability has made Code 39 an enduring standard in applications where data content matters as much as scanning speed. |
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2. Technical Foundations: How Code 39 Encodes Letters |
Before we explore the applications, it is helpful to understand the technical mechanism that enables Code 39 to handle alphanumeric data so naturally. The symbology's very name --- 'Code 3 of 9' --- reveals its encoding principle. |
The '3 of 9' Structure |
Each character in Code 39 is represented by a pattern of nine elements: five bars and four spaces . Of these nine elements, exactly three are wide and six are narrow . This consistent 'three wide' structure is why the barcode is called 'Code 3 of 9' or 'Code 39' . |
The wide elements are typically 2.5 to 3 times the width of the narrow elements, and this ratio provides the scanner with the information it needs to distinguish between the two states . The pattern of which of the nine positions are wide versus narrow determines which character is being encoded. For example, the letter 'A' has one specific pattern of wide bars and spaces, the letter 'B' another, and so on. |
The Character Set |
The standard Code 39 character set contains 43 distinct characters : |
- Digits: 0 through 9 |
- Uppercase letters: A through Z |
- Special characters: dash (-), period (.), space, dollar sign ($), slash (/), plus sign (+), and percent sign (%) |
The asterisk (*) is reserved as the start and stop character, marking the beginning and end of every Code 39 barcode . This asterisk is not encoded as data --- it is a framing symbol that tells the scanner where the barcode begins and ends. |
The Self-Checking Property |
One of the most important technical features of Code 39 is that it is 'self-checking' . This means that a single printing defect --- such as a bar that is slightly too wide or too narrow --- cannot transform one valid character into another valid character . Each character's wide/narrow pattern is sufficiently distinct from all others that the error would instead create an invalid pattern that the scanner would reject . |
This self-checking property is a direct consequence of the '3 of 9' encoding structure. Because each character must have exactly three wide elements, any error that changes the number of wide elements creates an invalid character. The scanner's decoder can detect this immediately and either reject the scan or, in some implementations, attempt to correct it. |
This feature is particularly valuable in industrial environments where barcodes may be printed on imperfect surfaces, subjected to wear, or scanned in less-than-ideal lighting conditions. It is also why Code 39 does not require a mandatory check digit, unlike many other symbologies . However, it is important to note that many industry specifications do mandate the use of an optional Modulo 43 check digit for additional data integrity assurance . |
Full ASCII Extension |
It is worth noting that the standard Code 39 character set is limited to uppercase letters. If lower-case letters or the full 128-character ASCII set are required, an extension known as 'Code 39 Full ASCII' or 'Code 39 Extended' is available. This extension encodes all ASCII characters by combining pairs of standard Code 39 characters . For instance, lower-case 'a' is encoded as '+A' in the extended scheme . While this doubles the barcode length for extended characters, it provides full ASCII support without requiring a change to the underlying symbology structure. |
In practice, most industrial applications that use Code 39 are satisfied with uppercase alphanumeric characters, and the extended version is used less frequently. However, the existence of the extension demonstrates the flexibility built into the Code 39 standard. |
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3. The Alphanumeric Advantage in Practice |
The technical capability to encode letters and numbers together translates into significant practical advantages. Let us examine how this capability supports real-world applications. |
Part Numbers as First-Class Data |
In engineering and manufacturing, part numbers are rarely purely numeric. They are structured identifiers that often include prefixes indicating product families, suffixes indicating revisions, and embedded letters that carry semantic meaning. For example, consider the part number 'MTR-8942-REV-C'. The 'MTR' prefix indicates 'Motor', the '8942' is the base model number, and 'REV-C' indicates revision C. |
If a barcode symbology can only encode numbers, this part number would have to be translated into a purely numeric code, such as '89423' (where 3 might represent revision C). This translation creates several problems: |
1. Loss of human readability: The numeric code no longer carries the meaning that the original part number conveyed. |
2. Mapping complexity: A separate system is needed to translate between the numeric code and the actual part number. |
3. Error risk: Any error in the mapping or translation can result in the wrong part being identified. |
Code 39 solves this problem by allowing the part number to be encoded exactly as it appears in the engineering documentation . The barcode can read 'MTR-8942-REV-C' directly, preserving the full meaning of the identifier. The scanner produces this alphanumeric string, which can be looked up directly in the inventory database without any translation step. |
Legacy System Compatibility |
Many organizations have decades of investment in alphanumeric part numbering systems. These systems predate barcodes and were designed for human readability and logical organization. Migrating to a purely numeric scheme would be expensive, error-prone, and disruptive. |
Code 39 allows these organizations to implement barcode tracking without abandoning their established part numbering conventions. The same part numbers that appear on engineering drawings, purchase orders, and inventory lists can appear on barcode labels. This compatibility reduces training requirements, minimizes errors, and preserves the organizational knowledge embedded in the part numbering system. |
Variable-Length Flexibility |
Another advantage of Code 39 is its variable-length encoding. Unlike UPC, which has a fixed length of 12 or 13 digits, Code 39 can encode data of any length . This is important because alphanumeric part numbers come in a wide variety of lengths. Some may be short, like 'A-1', while others may be long, like 'ASSY-2345-REV-D-SUB'. |
The combination of alphanumeric encoding and variable length makes Code 39 remarkably versatile. A single barcode symbology can handle almost any internal identification scheme an organization might devise, without requiring the data to be padded, truncated, or reformatted. |
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4. Industry Application: United States Military and LOGMARS |
Perhaps the most significant endorsement of Code 39's alphanumeric capability comes from the United States Department of Defense. The military's LOGMARS (Logistics Applications of Automated Marking and Reading Symbols) program adopted Code 39 as the standard symbology for identifying government property . |
The LOGMARS Requirement |
The LOGMARS program, initiated in the 1980s, aimed to improve the efficiency and accuracy of military logistics by using barcodes to track equipment, supplies, and parts throughout their lifecycle. The military's inventory includes an immense variety of items --- from small electronic components to large vehicles --- each with its own alphanumeric National Stock Number (NSN) and other identifiers. |
The choice of Code 39 for LOGMARS was driven by several factors, but the alphanumeric capability was paramount. Military part numbers are inherently alphanumeric, incorporating letters that indicate the type of item, the service branch, and various other attributes. A symbology that could encode only numbers would have required a major overhaul of the military's identification system. |
MIL-STD-130 and the Standard Practice |
The military's requirements are formalized in MIL-STD-130, which specifies the marking of U.S. military property . This standard mandates the use of Code 39 (among other symbologies) for item identification and requires a Modulo 43 check digit for additional data integrity . |
This military endorsement has had a ripple effect throughout the defense industry. Contractors supplying parts to the military must comply with MIL-STD-130, which means they must implement Code 39 in their own barcoding systems. This has created a large installed base of Code 39-compatible scanners, printers, and software, reinforcing the symbology's position in the market. |
Beyond Logistics: Defense Applications |
Beyond basic logistics, Code 39 is used throughout the defense sector for tracking assets, managing maintenance records, and documenting equipment configurations. In these applications, the alphanumeric capability is essential because equipment identifiers often include both letters and numbers. |
For instance, an aircraft component might have an identifier like 'APU-1234-ALT'. This identifier combines an abbreviation ('APU' for Auxiliary Power Unit), a numeric model number, and a suffix indicating an alternate version. Code 39 encodes this identifier directly, allowing maintenance technicians to scan it and retrieve the complete maintenance history for that specific component. |
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5. Industry Application: Automotive Manufacturing |
The automotive industry, like the military, has extensive alphanumeric identification requirements. The Automotive Industry Action Group (AIAG) has established standards for barcoding that include Code 39 as a recognized symbology . |
The Automotive Supply Chain |
Automotive manufacturing involves complex supply chains with multiple tiers of suppliers. A single vehicle contains thousands of components, each sourced from different suppliers and each with its own part number. These part numbers are typically alphanumeric, incorporating letters that indicate the component type, the vehicle model, the manufacturing plant, and other attributes. |
The AIAG B-1 standard, which defines barcode labeling for automotive parts, accommodates Code 39 for alphanumeric applications . This standard ensures that a part manufactured in one country can be scanned and identified consistently when it arrives at an assembly plant in another country. |
Traceability and Recall Management |
One of the most critical applications of barcodes in the automotive industry is traceability --- the ability to track a component from its origin through its entire lifecycle. In the event of a safety recall, manufacturers need to identify exactly which vehicles contain a specific batch of components. |
The alphanumeric capability of Code 39 supports this traceability by allowing component identifiers to include not just the part number, but also batch codes, date codes, and supplier codes --- all of which may include letters. For example, a component might be labeled 'BRK-8942-BATCH-C-0315', where 'BRK' indicates a brake component, '8942' is the model, 'BATCH-C' identifies the production batch, and '0315' is the date code. |
Plant Floor Applications |
Within automotive assembly plants, Code 39 is used for tracking work-in-progress, managing tool inventory, and routing materials. In these environments, the ability to encode letters directly is a practical necessity. Tool cribs, for instance, often use identifiers like 'WRENCH-T-15' or 'TORQUE-TOOL-3A' --- codes that mix letters and numbers in a way that is immediately understandable to workers. |
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6. Industry Application: Healthcare and Medical Device Tracking |
The healthcare sector has its own complex alphanumeric identification needs. Medical devices, pharmaceuticals, and patient records all require unique identifiers that often combine letters and numbers. |
The Health Industry Bar Code Standard |
The Health Industry Bar Code (HIBC) standard, developed by the Health Industry Business Communications Council (HIBCC), builds on Code 39 as one of its primary symbologies . The HIBC standard is used for labeling medical devices, pharmaceuticals, and other healthcare products throughout their supply chain. |
Medical Device Identification |
Medical devices --- from surgical instruments to implantable devices --- have identifiers that typically include letters indicating the manufacturer, the product family, and the specific model. For example, a surgical implant might have an identifier like 'JNJ-7890-XL', where 'JNJ' indicates Johnson & Johnson, '7890' is the product code, and 'XL' indicates the size. |
The alphanumeric capability of Code 39 allows these identifiers to be encoded directly on the product label. This is essential for ensuring that the correct device is used for the correct patient and that the device can be tracked throughout its lifecycle. |
Patient Safety Applications |
Beyond product labeling, Code 39 is used in healthcare for patient identification, specimen tracking, and medication administration. In these applications, the barcode might encode a patient identifier like 'SMITH-J-7890-3' --- a mix of letters and numbers that uniquely identifies a patient while also being human-readable. |
Regulatory Requirements |
Regulatory requirements in healthcare often mandate specific labeling formats that include alphanumeric data. For instance, the U.S. Food and Drug Administration's Unique Device Identification (UDI) system requires that medical devices carry identifiers that include the device identifier (DI) and production identifier (PI). These identifiers incorporate both letters and numbers, and Code 39 is one of the accepted symbologies for UDI labeling. |
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7. Industry Application: Electronics and High-Tech Manufacturing |
The electronics industry, with its rapid product cycles and dense supply chains, has found Code 39 useful for a variety of tracking applications. |
Component Tracking |
Electronic components --- resistors, capacitors, integrated circuits, and the like --- often have alphanumeric part numbers that follow industry-standard naming conventions. These numbers typically include letters indicating the component type, the manufacturer, and various specifications. |
For example, a resistor might have the identifier 'RC-0805-10K-5%', where 'RC' indicates a resistor, '0805' is the package size, '10K' is the resistance value, and '5%' is the tolerance. Code 39 encodes this identifier directly on the component's packaging, allowing automated inventory systems to track quantities and manage reordering. |
Printed Circuit Board Assembly |
In printed circuit board (PCB) assembly, panels of boards are often tracked using barcodes that include the board's revision level, the date of manufacture, and the assembly line identifier. These identifiers are typically alphanumeric. For instance, 'PCB-7890-REV-D-24-01-15' might indicate a specific board revision produced on a specific date. |
The ability to encode this alphanumeric data directly is valuable because it allows the production history of each board to be recorded and retrieved. If a defect is discovered in a specific revision, the manufacturer can use the barcode data to identify all boards from that revision that are still in the field. |
Warehousing and Inventory |
In electronics warehouses, Code 39 is used alongside Code 128 and other symbologies for inventory management . The alphanumeric capability is valuable here because electronics part numbers are almost invariably alphanumeric. By encoding these part numbers directly on the warehouse bin labels and product packaging, Code 39 enables efficient put-away, picking, and cycle counting. |
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8. Industry Application: Government and Public Sector |
Beyond the military, Code 39 is used by various government agencies and public sector organizations for asset tracking, document management, and identification. |
Government Property Management |
Federal, state, and local governments maintain extensive inventories of equipment --- vehicles, computers, office furniture, and specialized equipment. Each item typically has a property tag with an alphanumeric identifier that might include the agency name, the equipment type, and a sequence number. |
Code 39 encodes these identifiers on the property tags, allowing government staff to conduct physical inventories, track equipment movements, and report on asset utilization. The alphanumeric capability ensures that the identifier on the tag matches the identifier in the property management system, reducing the risk of data entry errors. |
Library Systems |
Many libraries use Code 39 for barcoding books and other materials . Library barcodes typically encode the item's accession number --- an alphanumeric identifier assigned when the item is cataloged. This identifier might include letters indicating the library branch, the collection, and the item type. |
The variable-length feature of Code 39 is particularly useful in libraries, where accession numbers can vary in length depending on the size of the collection. A small library might use short accession numbers like 'A-123', while a large library might need longer ones like 'MAIN-REF-7890'. |
Document and File Tracking |
Government agencies and corporations alike use Code 39 for tracking documents and files. The barcode is applied to file folders, and the encoded identifier is linked to a database that stores the document's title, location, and access history. |
Document identifiers are frequently alphanumeric, incorporating letters that indicate the department, the file series, and other attributes. For instance, 'HR-POLICY-2024-001' might be the identifier for the first human resources policy document of 2024. Code 39 encodes this identifier directly, making it easy to scan the folder and retrieve the associated document information. |
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9. Industry Application: Transportation and Logistics |
The transportation and logistics industry uses barcodes extensively for tracking shipments, managing fleets, and routing packages. |
Shipment Tracking |
Shipment tracking numbers, such as those used by freight carriers, often combine letters and numbers. For example, a tracking number might be 'FEDEX-7890123456' or 'UPS-1Z-999-999-99'. Code 39 encodes these tracking numbers directly on shipping labels, allowing carriers to scan them at multiple points in the delivery process. |
The self-checking property of Code 39 is particularly valuable in this environment, where barcode labels may be subjected to rough handling, weather exposure, and other conditions that can cause printing defects . |
Fleet Management |
Transportation companies use barcodes to track vehicles, trailers, and containers. These assets typically have alphanumeric identifiers assigned by the company or by regulatory agencies. For instance, a trailer might be identified as 'TRAILER-12345-ABC', which combines a descriptive prefix, a numeric sequence, and a suffix that may indicate the trailer's owner or registration status. |
Intermodal Logistics |
In intermodal logistics --- where shipments move across multiple modes of transportation (truck, rail, ship) --- consistent identification is essential. Code 39's alphanumeric capability allows the same identifier to be used throughout the journey, regardless of the mode of transport or the systems used by different carriers. |
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10. Industry Application: Education and Institutional Use |
Educational institutions, from K-12 schools to universities, use Code 39 for various tracking applications. |
Asset Management |
Schools and universities typically own thousands of assets --- computers, projectors, furniture, musical instruments, scientific equipment, and athletic gear. Each asset needs to be tracked for inventory purposes, and the identifiers are often alphanumeric. |
For example, a projector might be tagged as 'PROJ-2024-123', where 'PROJ' indicates a projector, '2024' is the year of acquisition, and '123' is a sequence number. Code 39 encodes this identifier on an asset tag, allowing the institution to conduct annual inventories and track equipment movements. |
Identification Cards |
Many educational institutions use Code 39 on student and staff identification cards . The barcode might encode the individual's ID number --- which is often alphanumeric --- along with other information such as the issue date or expiration date. |
The use of Code 39 on ID cards is possible because the symbology's variable-length, alphanumeric character set can accommodate the diverse formats used by different institutions. A university might use IDs like 'STU-2024-12345', while a high school might use 'HS-2024-ABCD'. |
Library Systems |
As mentioned earlier, libraries are major users of Code 39 for barcoding books and other materials. This application extends to school libraries, public libraries, and university libraries --- essentially any institution that manages a large collection of physical items. |
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11. Code 39 in the Context of Other Symbologies |
To fully appreciate the alphanumeric advantage of Code 39, it is helpful to compare it with other common barcode symbologies. |
Numeric-Only Symbologies |
Interleaved 2 of 5 (ITF): This symbology is popular in warehouse applications for case-level tracking . It encodes only digits 0 through 9, and it is variable-length. While it offers good density for numeric data, it simply cannot handle letters. A warehouse using ITF for pallet tracking would have to map alphanumeric part numbers to numeric equivalents, with all the associated complexity and risk. |
UPC (Universal Product Code): This is the standard retail barcode found on virtually every consumer product in the United States . It is numeric-only and fixed-length (12 digits). UPC is excellent for its intended purpose --- identifying consumer products at point-of-sale --- but it is completely unsuitable for alphanumeric part numbers. |
EAN (European Article Number): This is the European equivalent of UPC, also numeric-only and fixed-length . Like UPC, it cannot handle letters. |
Other Alphanumeric Symbologies |
Code 128: This symbology is a more compact alternative to Code 39, offering higher data density and the ability to encode the full ASCII character set without the paired encoding scheme required by Code 39 Extended . Code 128 is widely used in logistics, shipping, and manufacturing applications where label space is constrained. |
However, Code 128 is not as widely supported by legacy scanning equipment as Code 39 . Many older barcode readers were designed to decode Code 39 but may not support Code 128. Additionally, Code 128 is not self-checking in the same way as Code 39 --- it relies on a mandatory check digit for error detection. |
Code 93: This is a more compact evolution of Code 39 that can encode the same character set in less space . However, Code 39 remains more widely supported and easier to implement . |
Codabar: This symbology, also known as Codeabar, is used in some library and medical applications. It encodes digits 0-9, the letters A-D, and several special characters. However, its character set is more limited than Code 39's, and it is less widely used. |
The Choice of Symbology |
The choice between these symbologies depends on the specific requirements of the application. If the data is purely numeric and high density is important, Interleaved 2 of 5 or Code 128 may be good choices. If alphanumeric data is required and density is less critical than compatibility and self-checking reliability, Code 39 is often the preferred choice. |
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12. Technical Limitations and Their Impact on Applications |
While Code 39's alphanumeric capability is a major advantage, it is important to understand the technical limitations that affect its use in different applications. |
Data Density |
Code 39 is a relatively low-density symbology. Each character requires nine elements (five bars and four spaces), plus an inter-character gap . This means that a Code 39 barcode is significantly longer than a Code 128 barcode encoding the same data --- approximately 40% longer for a 10-character barcode . |
This low density has practical implications. In applications where label space is constrained --- such as small electronic components or medical devices --- Code 39 may not be the best choice. The barcode would need to be printed very small to fit on the label, which can make it difficult to scan reliably. In these cases, a higher-density symbology like Code 128 or a 2D symbology like Data Matrix might be preferable . |
Character Set Limitations |
Standard Code 39 supports only uppercase letters, digits, and a limited set of special characters . If the data includes lowercase letters, symbols like @ or , or non-ASCII characters, the Full ASCII extension is required, which effectively doubles the barcode length for those characters . |
This limitation affects applications where the identifier includes lowercase letters or a wide range of special characters. For instance, if a part number includes a pound sign () or an ampersand (&), the standard Code 39 character set cannot encode it directly. The Full ASCII extension would be needed, increasing the barcode length. |
Practical Length Limits |
Although Code 39 has no theoretical length limit, practical considerations limit most implementations to 20 to 50 characters . Beyond this length, the barcode becomes physically long, which can make it difficult to scan and can exceed the space available on the label. |
This length limitation affects applications where the identifier is very long. For example, if the data to be encoded is a descriptive string like 'LEFT-HAND-ASSEMBLY-FOR-MODEL-7890-REV-D', it may be too long for a Code 39 barcode to be practical. |
Scanning Reliability |
While Code 39's self-checking property improves error detection, the symbology's low density means that scanners must have sufficient resolution to distinguish between the wide and narrow elements. If the barcode is printed too small or the scanner is not optimized for Code 39, scanning reliability can suffer . |
This affects applications where barcodes must be scanned by consumer-grade devices, such as smartphones. While many mobile scanning apps support Code 39, camera-based scanning may be less reliable than dedicated laser scanners, especially with small or low-quality barcodes . |
Check Digit Requirements |
Although Code 39 is self-checking and does not require a mandatory check digit, many industry specifications mandate the use of a Modulo 43 check digit for added safety . This adds one more character to the barcode length, further reducing density, but it can significantly improve data integrity in critical applications. |
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13. Mitigating the Limitations: Practical Implementation Strategies |
Despite these limitations, Code 39 remains a practical choice for many applications. Organizations that implement Code 39 can use several strategies to mitigate the limitations while preserving the alphanumeric advantage. |
Sizing and Print Quality |
One of the most important factors in successful Code 39 implementation is ensuring adequate sizing and print quality. The minimum X dimension (the width of the narrowest element) should be at least 0.19 millimeters (7.5 mils) for general use . The quiet zones --- the blank spaces on either side of the barcode --- should be at least 10 times the X dimension . |
Proper printing is also essential. Laser printers and thermal transfer printers produce the best results for Code 39. Direct thermal labels can be used but are more susceptible to fading and damage. |
Using Check Digits Appropriately |
The optional Modulo 43 check digit is recommended for critical applications where data integrity is paramount . The check digit is computed from the data characters and appended to the barcode. When the barcode is scanned, the decoder computes the check digit from the data and compares it to the check digit encoded in the barcode. If they match, the data is accepted. If they do not match, an error is indicated. |
The check digit adds one character to the barcode length, reducing density slightly, but it provides an additional layer of error detection. For military, aerospace, and healthcare applications, where errors can have serious consequences, the check digit is highly recommended. |
Using Extended Code 39 When Needed |
If the data includes lowercase letters or special characters that are not in the standard Code 39 character set, the Full ASCII extension can be used . This extension uses pairs of standard Code 39 characters to encode each extended character, which doubles the barcode length for those characters. |
While this length increase is not desirable, it allows Code 39 to handle virtually any data that might need to be encoded in a barcode. The extension ensures that the same infrastructure --- scanners, printers, software --- can be used regardless of the character set. |
Considering Alternative Symbologies |
In some cases, Code 39 may not be the best choice, and a higher-density symbology like Code 128 or a 2D symbology like Data Matrix may be more appropriate. These alternatives offer greater density and more extensive character set support. |
However, switching to a different symbology requires careful consideration of the existing infrastructure. If the organization has a large installed base of Code 39 scanners, or if the application requires compatibility with external partners that use Code 39, the switch may be difficult or costly. |
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14. The Enduring Relevance of Code 39 |
In an era of rapidly evolving technology, one might wonder why a barcode symbology introduced in 1974 remains relevant . The answer lies in the combination of technical robustness, simplicity, and the alphanumeric capability that we have explored in this chapter. |
Legacy Infrastructure |
Perhaps the most significant factor in Code 39's enduring relevance is the installed base of compatible equipment. Millions of barcode scanners, printers, and software systems are designed to handle Code 39. For many organizations, replacing this infrastructure is not economically justifiable. |
This legacy factor is self-reinforcing. As long as Code 39 remains in widespread use, new scanners and printers will continue to support it, ensuring that new implementations can coexist with legacy ones. |
Simplicity and Reliability |
Code 39 is fundamentally simple. Its '3 of 9' encoding structure is easy to understand and implement . This simplicity translates into reliability. There are fewer things that can go wrong in the encoding and decoding process, and the self-checking property provides an extra layer of assurance. |
Alphanumeric Capability |
The alphanumeric capability that we have focused on in this chapter is a primary driver of Code 39's continued use. As long as organizations use alphanumeric identifiers --- and they will, because alphanumeric identifiers are human-readable and semantically meaningful --- there will be a need for a barcode symbology that can encode them directly. Code 39 meets this need effectively. |
Versatility |
We have explored Code 39's use across military, automotive, healthcare, electronics, government, transportation, and education sectors. This diversity is a testament to the symbology's versatility. Whether the application is tracking a military part, a medical device, or a library book, Code 39 provides a consistent solution. |
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15. Case Study: SEW-Eurodrive's DriveTag Program |
A concrete example of Code 39's continuing relevance can be found in the DriveTag program from SEW-Eurodrive, a leading manufacturer of drive technology products . |
The DriveTag program is a customized barcode labeling service that allows customers to define the data encoded on product labels . Customers can choose to include data such as material number, purchase order, project number, and serial number --- data that is typically alphanumeric. |
DriveTags are available in multiple barcode formats, including DataMatrix, Code 39, Code 128, and PDF417 . This flexibility ensures compatibility with existing scanners and data-capture systems, allowing customers to integrate the DriveTag with their existing enterprise resource planning (ERP) and inventory management systems . |
SEW-Eurodrive's decision to include Code 39 as one of the available formats reflects the symbology's continued relevance in industrial applications. Many of SEW-Eurodrive's customers have existing Code 39 infrastructure, and the company's DriveTag program accommodates those customers without requiring them to upgrade their scanning equipment. |
This case study illustrates several key points about Code 39 in practice: |
Alphanumeric data is the norm: The data that customers want to include in DriveTags --- material numbers, project numbers, serial numbers --- is typically alphanumeric. |
Legacy compatibility matters: By supporting Code 39, SEW-Eurodrive ensures that DriveTags are compatible with the existing infrastructure of their customers. |
Multiple symbologies coexist: The availability of multiple formats (DataMatrix, Code 39, Code 128, PDF417) reflects the reality that different applications and different customers have different requirements. Code 39 remains one of the valid options. |
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16. Conclusion: The Alphanumeric Native Advantage |
We have explored, in considerable detail, the alphanumeric native advantage of Code 39 and how this technical characteristic shapes the symbology's use across a wide range of industries. |
Summary of Technical Characteristics |
Let us begin by summarizing the key technical characteristics of Code 39 that support its alphanumeric capability: |
1. Alphanumeric character set: Standard Code 39 encodes uppercase letters A-Z, digits 0-9, and seven special characters (space, -, ., $, /, +, %) --- a total of 43 characters . This is the core advantage that differentiates Code 39 from numeric-only symbologies. |
2. Variable length: Code 39 can encode data of any length, accommodating both short and long identifiers . This flexibility is essential because alphanumeric part numbers come in varying lengths. |
3. Self-checking: Each Code 39 character's encoding pattern is sufficiently distinct that a single print defect cannot transform one valid character into another . This property reduces the need for a mandatory check digit, though industry specifications often recommend one. |
4. Optional check digit: A Modulo 43 check digit is available for applications requiring enhanced data integrity . |
5. Full ASCII extension: Extended Code 39 can encode all 128 ASCII characters by combining pairs of standard characters, providing flexibility for applications with more demanding character set requirements . |
6. Wide/narrow encoding: The '3 of 9' structure, where exactly three of nine elements are wide, provides a robust mechanism for encoding data that is tolerant of printing variations . |
7. Low density: Code 39's encoding structure results in longer barcodes than more compact symbologies like Code 128 . This is the primary limitation that must be considered in implementation. |
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Summary of Applications and Use Cases |
We have examined how these technical characteristics apply across multiple industries: |
United States Military (LOGMARS/MIL-STD-130): The military uses Code 39 to label government property, driven by the symbology's alphanumeric capability and the need for compatibility with established military identification systems . MIL-STD-130 mandates the use of a Modulo 43 check digit for added safety . |
Automotive Manufacturing: The AIAG B-1 standard accommodates Code 39 for alphanumeric part labels, supporting traceability across the automotive supply chain . The symbology's self-checking property is valuable in environments where labels may be exposed to oils, temperature extremes, and physical wear. |
Healthcare: The HIBC standard builds on Code 39 for medical device tracking and pharmaceutical labeling . The alphanumeric capability is essential for encoding device identifiers that include manufacturer codes, product families, and size or variant information. |
Electronics and High-Tech Manufacturing: Code 39 is used for component tracking in electronics manufacturing, where part numbers are typically alphanumeric . The variable-length feature accommodates the variety of part number formats used in the industry. |
Government and Public Sector: Code 39 is used for asset tracking, library systems, and document management in government agencies and public institutions . The symbology's simplicity and compatibility with legacy systems make it a practical choice. |
Transportation and Logistics: Code 39 encodes shipment tracking numbers, asset identifiers, and fleet management codes . The self-checking property is valuable in environments where labels may be exposed to rough handling. |
Education: Educational institutions use Code 39 for asset management, library systems, and ID cards . The alphanumeric character set accommodates the diverse identifiers used in school and university settings. |
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The Alphanumeric Native Advantage in Practice |
Across all of these applications, a common theme emerges: the alphanumeric native capability of Code 39 is not just a technical detail --- it is a practical necessity. Organizations use identifiers that include letters because those letters carry meaning. They convey information about product families, revisions, categories, origins, and more. These alphanumeric identifiers are integrated into engineering documentation, procurement systems, and inventory databases. To encode them in a purely numeric format would introduce complexity, risk, and cost. |
Code 39 solves this problem by encoding alphanumeric identifiers directly. It preserves the human-readable meaning of the identifier while enabling automated scanning and tracking. This direct encoding reduces the risk of translation errors, simplifies system integration, and supports the established identification conventions that organizations have developed over decades. |
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The Right Tool for the Right Job |
It is important to note that Code 39 is not the answer to every barcoding need. Its low density makes it less suitable for applications with very limited label space or very long identifiers. For such applications, Code 128 or 2D symbologies like DataMatrix may be more appropriate. |
However, where alphanumeric data is required, where label space is adequate, and where compatibility with existing infrastructure is important, Code 39 remains a robust and reliable choice. Its self-checking property provides an additional layer of error detection, and its optional check digit allows for enhanced data integrity in critical applications. |
The symbology's long history and widespread adoption have created an ecosystem of compatible scanners, printers, and software that make it easy to implement and maintain. For organizations with significant investment in Code 39 infrastructure, changing to a different symbology would be costly and disruptive. |
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Looking to the Future |
As technology continues to evolve, barcode applications will become more sophisticated. The rise of 2D symbologies like QR codes and DataMatrix codes, and the increasing use of Radio Frequency Identification (RFID), will create new possibilities for tracking and identification. |
However, these newer technologies do not obsolete Code 39. They augment it. For many industrial, military, and institutional applications, the simple, reliable, alphanumeric barcode remains the most practical solution. The combination of Code 39's alphanumeric capability, self-checking property, and wide support ensures that it will continue to be a useful tool for years to come. |
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References |
The information in this chapter draws on the following sources: |
1. BarcodeFYI, 'Code 39 Explained: The Self-Checking Alphanumeric Barcode' |
2. Aspose, 'What is Code 39 BarcodeUses, Structure & Generation Guide' |
3. Aspose Documentation, 'Code 39 Info Card' |
4. Cognex, 'Supported Symbologies' |
5. BarcodeFYI, 'Code 39 --- Barcode Symbology Guide' |
6. Pit & Quarry, 'SEW-Eurodrive's DriveTag connects labels to enterprise systems' |
7. Stemmer Imaging, 'Barcode > Theory of Operation > Information on Barcode types' |
8. Cognex, 'Code 39 Barcodes: How They Work' |
9. Material Handling 24/7, 'Understanding Barcode Types: A Complete Guide to Barcode Symbologies and Their Uses' |
10. BarcodeFYI, 'Character Encoding in Barcodes: Digits, Letters, and Binary' |
*End of Chapter 35* |
cs@easiersoft.com