Chapter 7: The 9-Element Pattern |
A Brief Summary |
Code 39, often called 'Code 3 of 9,' derives its name from a simple yet elegant encoding scheme: each character in the barcode is represented by nine elements---five bars and four spaces---of which exactly three are wide and six are narrow. With nine total positions and exactly three wide elements, the theoretical number of possible combinations is 84. Yet of these 84 possible patterns, only 43 are used to represent data characters, with an additional pattern reserved for the start and stop character (the asterisk). This chapter explores the technical foundations of this encoding pattern and, more importantly, examines how the unique characteristics of Code 39---its self-checking nature, alphanumeric capability, variable length, and relatively low data density---have shaped its adoption across diverse industries. From military logistics to healthcare, automotive manufacturing to library management, the 9-element pattern has proven remarkably resilient, remaining in active use decades after its introduction in 1974. What follows is a detailed exploration of these real-world applications and the technical properties that make Code 39 particularly suited---or sometimes ill-suited---for each. |
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1. The Technical Foundation of the 9-Element Pattern |
Before diving into applications, it is worth understanding precisely what the '9-element pattern' means and why it matters. Code 39 was developed in 1974 by David Allais and Raymond Stevens, then working at Interface Mechanisms Inc., which later became Intermec Corporation . It was the first barcode symbology capable of encoding alphabetic characters alongside numeric digits---a significant breakthrough at the time . |
Each character in Code 39 is composed of five bars and four spaces, totaling nine elements. Among these nine elements, exactly three are wide and six are narrow . This is why the symbology is sometimes called 'Code 3 of 9.' The wide-to-narrow ratio is typically between 2.0:1 and 3.0:1, though the specification allows a range of approximately 1.8 to 3.4 . |
The theoretical number of combinations for choosing 3 positions out of 9 is 84. However, only 43 of these combinations are assigned to characters: the digits 0 through 9, the uppercase letters A through Z, and seven special characters (space, minus, period, dollar sign, slash, plus, and percent) . The asterisk (*) serves as the start and stop character, signaling the beginning and end of the barcode to the scanner . |
This encoding scheme has several important consequences. First, because the wide/narrow pattern for each character is unique and sufficiently distinct, Code 39 is considered 'self-checking' . A single printing defect that causes a narrow bar to appear wide or vice versa will typically produce an invalid character pattern rather than a different valid character, providing inherent error detection without requiring a separate check digit. Second, the use of a variable number of characters per barcode means Code 39 can encode messages of any length, within practical limits. Third, the requirement for exactly three wide elements per character means each character occupies roughly the same physical space, simplifying decoding. |
However, this encoding approach also has drawbacks. The most significant is low data density: because each character requires nine elements plus an inter-character gap, Code 39 barcodes are roughly 30 to 40 percent wider than equivalent Code 128 barcodes . For applications that require encoding large amounts of data, this can result in impractically long barcodes that may not fit on small labels . |
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2. The Military and LOGMARS: Where It All Began |
Perhaps the most significant factor in Code 39's widespread adoption was its selection for the United States Department of Defense's LOGMARS (Logistics Applications of Automated Marking and Reading Symbols) program . This program mandated the use of Code 39 for marking all military property, creating an enormous installed base of equipment, procedures, and expertise. |
Technical Factors Behind Military Adoption |
The military chose Code 39 for several compelling reasons that align with its technical characteristics. First, the need to track equipment by alphanumeric serial numbers and part numbers required a symbology that could encode letters as well as digits---a capability earlier barcodes lacked . Second, the self-checking property was highly valued in military logistics environments where labels might be subjected to harsh conditions, including abrasion, exposure to chemicals, and extreme temperatures. The ability to detect encoding errors without relying on a check digit calculation (though a Modulo 43 check digit was often added per MIL-STD-130) provided robustness . |
Practical Application in Military Logistics |
In practice, LOGMARS involved marking everything from individual components and spare parts to shipping containers and vehicles with Code 39 labels. A typical military logistics operation might involve receiving shipments of parts, each bearing a Code 39 label encoding the National Stock Number (NSN), quantity, and condition code. Personnel would scan these labels with handheld readers, automatically updating inventory systems and reducing the errors inherent in manual data entry. |
The variable-length nature of Code 39 proved advantageous here: a simple part number might require only a few characters, while a more complex item with multiple identifiers could accommodate longer codes without requiring changes to the basic symbology. The start and stop asterisks provided reliable framing for the scanner, allowing it to distinguish a Code 39 symbol from other barcode types that might appear nearby . |
Long-Term Impact |
The LOGMARS mandate created a self-reinforcing cycle: as more military suppliers adopted Code 39 to comply with labeling requirements, more barcode readers and printing systems were configured to support it. This installed base made Code 39 a default choice for many other government and commercial applications. Even after the original MIL-STD-1189 was superseded by ANSI/AIM BC1/1995, the legacy of military adoption ensured that Code 39 remained widely supported . |
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3. Automotive Industry: Tracking Parts Across the Supply Chain |
The automotive industry adopted Code 39 early and extensively, particularly through the Automotive Industry Action Group (AIAG), which established standards for part labeling . The AIAG B-1 standard, among others, specified Code 39 for various labeling applications, including parts identification, shipping labels, and component tracking. |
Why Code 39 Suits Automotive Applications |
Automotive manufacturing involves complex supply chains with thousands of suppliers providing parts that must be tracked from production through assembly to final vehicle delivery. Code 39's ability to encode alphanumeric part numbers, combined with its tolerance for the less-than-perfect printing conditions found on factory floors, made it a practical choice. |
The manufacturing environment presents challenges: labels may be exposed to oil, grease, and temperature variations. Code 39's self-checking property provides a level of robustness against label damage that some other symbologies lack. Additionally, the ability to use a barcode font on standard printers meant that suppliers could generate Code 39 labels without specialized equipment---a significant advantage in an industry where thousands of suppliers needed to comply with labeling standards. |
Vehicle Identification Number (VIN) Encoding |
A particularly important application in automotive is the encoding of Vehicle Identification Numbers, which are alphanumeric strings of 17 characters. Code 39's support for both letters and digits makes it a natural fit for VIN encoding. A typical VIN label on a vehicle component might include the full VIN, the part number, and date codes, all in a single barcode. |
However, the low data density of Code 39 poses challenges here. A 17-character VIN encoded in Code 39 requires a label significantly wider than one encoded in Code 128. For this reason, many newer automotive applications have transitioned to Code 128 or two-dimensional symbologies like Data Matrix . Yet the installed base of Code 39 readers and legacy systems means that Code 39 remains common, particularly in supplier labeling and aftermarket parts identification. |
Assembly Line Tracking |
On the assembly line itself, Code 39 labels are used to track work-in-progress. As vehicles move along the assembly line, each major component---engine, transmission, body panels---may bear a Code 39 label that encodes its serial number and specifications. Workers scan these labels to verify correct assembly, and the data feeds into production tracking systems. The simplicity of Code 39 encoding and decoding means that scanners can reliably read these labels even when they are partially obscured or dirty, a common occurrence in automotive assembly plants. |
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4. Healthcare: Patient Safety and Inventory Management |
The healthcare industry has been a significant adopter of Code 39, particularly through the Health Industry Bar Code (HIBC) standard, which builds on Code 39 for labeling medical products . The HIBC standard specifies the use of Code 39 for marking pharmaceuticals, medical devices, and patient identification wristbands. |
Patient Identification Wristbands |
One of the most critical applications in healthcare is patient identification. Hospitals worldwide use barcode wristbands to ensure that the right patient receives the right medication, procedure, or blood transfusion. Code 39's use in this application is driven by several factors. |
First, patient identification typically requires encoding a patient ID number, which may include letters and digits, along with a name or date of birth. Code 39's alphanumeric capability accommodates this easily. Second, wristbands are often printed on thermal printers at the point of care, where simplicity is paramount. Code 39 can be generated using simple barcode fonts, allowing integration with existing hospital information systems without complex printing infrastructure. |
Third, and perhaps most importantly, the healthcare environment demands extreme reliability. A misread patient ID could lead to a medical error with potentially fatal consequences. Code 39's self-checking property provides a measure of protection against misreads caused by wrinkled, smudged, or partially obscured wristbands. While not as robust as modern two-dimensional symbologies with error correction, Code 39's inherent error detection has contributed to patient safety in countless hospital settings. |
Pharmaceutical Labeling |
The pharmaceutical industry has used Code 39 extensively for labeling medication packaging. In Germany, for example, the IFA coding system uses Code 39 to encode the PZN (Pharmazentralnummer), a national product number for pharmaceuticals . This allows pharmacies to verify medication identity and track inventory electronically. |
However, pharmaceutical labeling presents challenges. Medication packages are often small, leaving limited space for barcodes. Code 39's relatively low data density means that longer codes may not fit on small packaging. For this reason, the pharmaceutical industry has been moving toward smaller, higher-density symbologies, particularly Data Matrix codes, which are used extensively in serialization and anti-counterfeiting efforts . |
The Full ASCII extension of Code 39 is sometimes used in healthcare applications where lowercase letters or control characters must be encoded, though this further reduces density since each extended character requires two Code 39 symbols . For example, the lowercase letter 'a' is encoded as '+A' in Full ASCII Code 39, doubling the space required . |
Medical Device Labeling |
Medical devices, ranging from surgical instruments to implantable devices, are often labeled with Code 39 barcodes for tracking through manufacturing and distribution. The HIBC standard provides a structured format for encoding manufacturer identification, product catalog numbers, and lot numbers in Code 39 symbols. |
One advantage of Code 39 in this context is its tolerance for labels that are applied to curved or uneven surfaces. Many medical devices have cylindrical or irregular shapes that can distort barcodes when printed on curved surfaces. Code 39's relatively simple encoding makes it more forgiving of such distortion than some other symbologies. However, the trend toward smaller device labeling, particularly for implantable devices with minimal surface area, has driven adoption of higher-density symbologies in recent years. |
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5. Logistics and Transportation: Tracking the Movement of Goods |
Logistics and transportation are among the most extensive users of Code 39, particularly for tracking shipments and packages . The symbology's versatility, combined with its widespread support in scanners and software, has made it a staple of shipping and receiving operations worldwide. |
Package Tracking |
Shipping companies and logistics providers use Code 39 labels to track packages as they move through the distribution network. A typical shipping label might include the tracking number, destination ZIP code, and service type, all encoded in Code 39. Workers scan these labels at each sorting facility, automatically updating the package's location in the tracking system. |
The variable-length nature of Code 39 is valuable here, as tracking numbers can vary in length between shipments. The encoding of alphanumeric characters accommodates modern tracking numbers, which often include both letters and digits. Furthermore, the start and stop characters provide reliable scanning even when the label is partially obscured or oriented at an angle---common conditions in high-volume sorting facilities where packages move rapidly on conveyor belts. |
Warehouse Management |
Within distribution centers and warehouses, Code 39 is used extensively for inventory management. Pallet labels, bin labels, and item labels often use Code 39 to encode product identifiers, locations, and quantities. Workers with handheld scanners verify inventory, process incoming shipments, and prepare outgoing orders by scanning these labels. |
The self-checking property is particularly valuable in warehousing, where labels may be exposed to dust, moisture, and rough handling. A misread in a warehouse can result in picking the wrong item for shipment, leading to customer dissatisfaction and additional shipping costs. Code 39's ability to detect and reject misreads helps prevent such errors. |
Transportation of Hazardous Materials |
A specialized application in logistics is the labeling of hazardous materials. Code 39 is used on shipping papers and package labels for hazardous waste and dangerous goods, encoding the UN identification number, hazard class, and other regulatory information. The reliability of Code 39 scanning in variable lighting conditions and the ability to encode the alphanumeric UN numbers make it suitable for this critical safety application. |
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6. Manufacturing and Industrial Asset Tracking |
Beyond the automotive sector, manufacturing companies across many industries use Code 39 for tracking equipment, tools, and raw materials. The symbology's ruggedness and simplicity are valued in industrial settings where reliability and ease of implementation often outweigh the benefits of higher-density alternatives. |
Fixed Asset Management |
Manufacturing plants have thousands of pieces of equipment---from large assembly line machinery to hand tools---that must be tracked for maintenance, calibration, and inventory purposes. Code 39 labels are applied to these assets, encoding unique equipment numbers that link to maintenance records, calibration schedules, and location information. |
The ability to generate Code 39 labels using simple barcode fonts on ordinary printers is a significant advantage here. Plant maintenance departments can print replacement labels on demand when existing labels become worn or damaged, without needing specialized printing equipment. This self-sufficiency reduces dependence on external suppliers and minimizes downtime. |
Work-in-Process Tracking |
On the factory floor, Code 39 is used to track work-in-process (WIP). As products move through manufacturing operations, each work-in-process unit bears a Code 39 label encoding its production order number, sequence number, and status. Workers scan the label at each operation, providing visibility into production status and enabling real-time tracking of throughput and yield. |
The tolerance of Code 39 to print quality variations is advantageous in this environment. Labels may be printed on demand at the work center using industrial printers that may not maintain perfect alignment or print quality. Code 39's wide/narrow ratio has a broad acceptable range, making it more forgiving of print quality variations than some other symbologies. |
Part Identification |
In electronics manufacturing, Code 39 is sometimes used for labeling printed circuit boards and components. However, the small size of electronic components poses a challenge for Code 39's low data density. A typical circuit board may require encoding an alphanumeric part number of 10 to 20 characters, which may not fit on the available label space. For this reason, electronics manufacturing has largely transitioned to higher-density symbologies, particularly Code 128 and Data Matrix codes, which can encode the same information in a smaller area. |
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7. Libraries and Document Management |
One of the most visible applications of Code 39 to the general public is in libraries, where it is used on books, DVDs, and library cards. The library community adopted Code 39 early, and the symbology remains widely used in library automation systems. |
Book Identification |
Library books typically bear a Code 39 label encoding the library's unique identifier for that item. When a patron checks out a book, the librarian scans the barcode to record the loan. When the book is returned, the barcode is scanned again to check it in. This simple but effective application streamlines library operations and reduces manual data entry errors. |
The alphanumeric capability of Code 39 is valuable here, as library item identifiers often include letters as well as digits. For example, a library might use an identifier like 'FIC12345' for a fiction book, where the prefix indicates the collection. Code 39 supports this without requiring special encoding. |
Self-Checkout Systems |
Self-checkout systems in libraries rely on Code 39 barcodes on books and patron library cards. Patrons scan their card and the books they wish to borrow, with the system automatically updating the circulation records. The reliability of Code 39 scanning is important here, as self-service systems must work reliably without staff intervention. |
The self-checking property provides a level of protection against scanning errors in self-checkout. If a barcode is partially damaged or poorly printed, the scanner is likely to reject it rather than read it incorrectly. This reduces the risk of a patron accidentally checking out the wrong book. |
Document Tracking |
In offices and government agencies, Code 39 is sometimes used for document tracking. Important documents---legal files, medical records, engineering drawings---may bear Code 39 labels that encode document numbers, version information, and location. The alphanumeric capability accommodates document numbering schemes that mix letters and digits. |
However, the low data density of Code 39 limits its use in document management for long document identifiers. A 20-character document number might require a Code 39 barcode several inches wide, which may not fit on a standard document. Many document management applications have adopted Code 128 or PDF417 for this reason. |
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8. Government and Regulatory Applications |
Beyond military use, various government agencies and regulatory bodies have adopted Code 39 for specific applications. The symbology's standardization and wide support make it an attractive choice for government labeling requirements. |
Federal Supply Chain Labeling |
The US General Services Administration and other federal agencies have specified Code 39 for various supply chain labeling applications. Government property must be marked according to standards that often require Code 39, perpetuating the symbology's use in federal logistics. |
The ISO/IEC 16388 standard defines Code 39 as an international standard, giving it regulatory legitimacy that some other symbologies lack . For applications requiring compliance with international standards, Code 39 is a proven choice. |
Patient Safety Regulations |
In healthcare, regulatory bodies in some countries have specified Code 39 for certain labeling applications, particularly in the context of the Unique Device Identification (UDI) system for medical devices. While the UDI standard allows multiple symbologies, some implementers have chosen Code 39 for its familiarity and reliability . |
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9. The Full ASCII Extension: Expanding the 9-Element Pattern |
Standard Code 39 encodes only 43 characters: uppercase letters, digits, and seven special characters. However, the Full ASCII extension (also called Code 39 Extended) allows encoding of all 128 ASCII characters by using pairs of standard Code 39 characters . |
How Full ASCII Works |
In Full ASCII mode, certain two-character combinations are interpreted as representing ASCII characters beyond the basic 43. For example, the lowercase letter 'a' is encoded as '+A', and the exclamation point is encoded as '/A' . A scanner configured for Full ASCII mode translates these combinations into the corresponding ASCII character. |
This extension effectively doubles the character set without changing the underlying 9-element pattern. However, it also doubles the length of the barcode for non-standard characters. A lowercase word like 'example' would encode as '+E+X+A+M+P+L+E', taking roughly twice the space of 'EXAMPLE' . |
Applications Requiring Full ASCII |
Full ASCII Code 39 is used in some legacy applications where lowercase letters, control characters, or punctuation beyond the basic 43 must be encoded. For example, some document management systems that encode filenames with lowercase letters may use Full ASCII Code 39. However, the density penalty is significant, and most modern applications use Code 128 or other symbologies that support full ASCII without the two-character encoding penalty. |
The Full ASCII mode also requires that scanners be configured accordingly. A scanner that is not in Full ASCII mode will transmit the individual characters rather than the intended ASCII character, potentially causing data corruption . For this reason, Full ASCII Code 39 is used primarily in closed-loop systems where scanner configuration can be controlled. |
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10. Strengths and Limitations in Practice |
Across these diverse industries, Code 39's strengths and limitations shape its application in predictable ways. Understanding these trade-offs is essential for selecting the appropriate symbology for any given application. |
Strengths in Practice |
The self-checking property is arguably Code 39's greatest practical strength. In environments where labels are subjected to abuse, the inherent error detection provides a level of reliability that some other symbologies require a check digit to achieve. This has made Code 39 the symbology of choice for applications where a misread could have serious consequences, such as patient identification and military logistics. |
The ability to encode both letters and digits was revolutionary in 1974 and remains valuable today. Many tracking applications require alphanumeric codes, and Code 39's straightforward encoding of all letters and digits makes it easy to implement without complex character mapping. |
The widespread availability of Code 39 support in scanners, printers, and software is perhaps its most important practical advantage. Because Code 39 has been in use for decades, nearly every barcode scanner sold today can read it, and nearly every barcode printing system can generate it. This ubiquity reduces implementation risk and ensures interoperability across different systems and organizations. |
The ability to generate Code 39 using simple barcode fonts is a significant operational advantage. Organizations can print Code 39 labels on ordinary laser or thermal printers without specialized software or hardware. This self-sufficiency is particularly valuable in distributed operations where labels must be printed at multiple locations. |
Limitations in Practice |
The low data density of Code 39 is its most significant practical limitation. A Code 39 barcode is roughly 30 to 40 percent wider than an equivalent Code 128 barcode . For long codes, this can produce barcodes that are impractically wide for the available label space. Small products, such as electronic components and pharmaceutical vials, simply cannot accommodate large Code 39 labels. |
The restriction to 43 characters in standard Code 39 is another limitation. Applications that require lowercase letters, extended punctuation, or control characters must use Full ASCII Code 39, which doubles the symbol width for these characters. This density penalty is often unacceptable in applications with limited label space. |
The absence of a mandatory check digit means that, while the self-checking property provides some error detection, it does not provide the mathematical certainty of a Modulo 43 or other check digit calculation. Although many specifications mandate a Modulo 43 check digit for Code 39, the check digit is optional in the base standard, and some implementations omit it, potentially increasing error risk. |
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11. The Evolution Toward Higher-Density Symbologies |
In many applications, Code 39 has been supplanted by higher-density symbologies, particularly Code 128 and two-dimensional symbologies like Data Matrix and QR Code. Understanding this evolution provides context for where Code 39 remains relevant today. |
Code 39 vs. Code 128 |
Code 128, introduced several years after Code 39, offers significantly higher density, encoding the same data in roughly 30 percent less space . It also supports all 128 ASCII characters natively, without the two-character encoding penalty of Full ASCII Code 39. For new applications, Code 128 is generally preferred over Code 39 for these reasons. |
However, Code 128 is more complex to implement and requires more sophisticated decoding algorithms. The installed base of Code 39 systems has created significant switching costs that have slowed the transition. In many organizations, legacy scanners, printers, and software are configured for Code 39, and changing to Code 128 would require expensive upgrades and retraining. |
Two-Dimensional Symbologies |
Two-dimensional symbologies like Data Matrix and QR Code offer densities orders of magnitude higher than any linear barcode, encoding hundreds of characters in a small area . These symbologies also provide error correction, allowing data to be recovered even when a significant portion of the symbol is damaged. |
In healthcare, pharmaceutical serialization and anti-counterfeiting initiatives have driven adoption of Data Matrix codes, which can encode lot numbers, expiration dates, and serial numbers in a small space that fits on individual medicine packages . In manufacturing, Data Matrix codes are used extensively for small-part marking, particularly in electronics and aerospace. These applications are effectively closed to Code 39 due to density and space constraints. |
Where Code 39 Persists |
Despite the advantages of higher-density symbologies, Code 39 persists in several categories of application. Where the installed base of Code 39 equipment is large and the cost of upgrading is prohibitive, organizations continue to use Code 39. This is particularly true in government and military logistics, where legacy systems and procurement cycles can span decades. |
Where the data to be encoded is short and label space is not a constraint, Code 39 remains a practical choice. Library book labels and simple inventory tags often require encoding only a few characters, and Code 39's simplicity and reliability are valued. In many warehouse operations, pallet labels with short product codes are still printed in Code 39 because existing scanning infrastructure supports it. |
Where decentralized printing using barcode fonts is important, Code 39 retains advantages. Because Code 39 can be generated with simple barcode fonts on ordinary printers, it is easier to implement in distributed printing environments than symbologies that require specialized software or encoding algorithms. This has kept Code 39 alive in applications where labels are printed at many different locations by personnel with varying levels of technical expertise. |
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12. Implementation Considerations for Code 39 |
For organizations implementing Code 39 today, several technical considerations affect the success of the application. |
Quiet Zone Requirements |
Every Code 39 barcode requires a quiet zone---a blank area at least 10 times the width of the narrow bar on each side of the symbol . This quiet zone allows scanners to detect the start and end of the symbol. Insufficient quiet zones can cause scanning failures, particularly with handheld scanners that may not be precisely aligned with the barcode. In practice, the quiet zone is often the most common implementation error. |
Wide-to-Narrow Ratio |
The wide-to-narrow ratio (typically 2.0:1 to 3.0:1) affects scan reliability . A higher ratio provides more distinct wide and narrow elements, improving scan reliability in challenging environments. However, a higher ratio also increases the overall symbol length, reducing density. Implementation specifications such as MIL-STD-130 often specify a minimum ratio to ensure reliability. |
Print Quality |
Like all barcodes, Code 39 requires adequate print quality for reliable scanning. Ink spread, which causes bars to widen and spaces to narrow, can cause decoding failures, particularly when the wide-to-narrow ratio is low. Thermal transfer printing generally produces the best quality Code 39 labels, while inkjet printing can be more variable. Implementation specifications often include print quality requirements to ensure reliable scanning. |
Human-Readable Text |
The practice of printing human-readable text beneath the barcode is nearly universal in Code 39 implementations. The text typically shows the encoded data, often with the asterisks omitted since the start and stop characters are not part of the data . This human-readable text provides a backup mechanism if scanning fails and helps personnel verify the encoded data visually. |
Check Digit Usage |
While the Code 39 standard does not require a check digit, many implementation specifications mandate the Modulo 43 check digit . The check digit is computed from the barcode data and encoded as an additional character. When the barcode is scanned, the reader recalculates the check digit and compares it to the encoded value, detecting most single-character errors. For applications where data integrity is critical, the check digit is strongly recommended. |
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13. Code 39 in the Future |
Looking ahead, Code 39's role in the barcode ecosystem is likely to continue diminishing, but its complete disappearance is unlikely in the foreseeable future. |
Legacy Systems |
The longevity of Code 39 in government and military logistics is perhaps its strongest guarantee of continued relevance. Government procurement cycles can span decades, and the cost of changing symbology across thousands of suppliers and tens of thousands of items is enormous. As long as the Department of Defense and other government agencies continue to specify Code 39, suppliers will continue to generate Code 39 labels. |
Similarly, in industries like automotive where Code 39 has been deeply embedded in supply chain standards, the transition to other symbologies is slow and incremental. New applications may use Code 128 or Data Matrix, but existing applications continue to use Code 39, and suppliers must maintain capabilities to generate and read both. |
Niche Applications |
There are niche applications where Code 39 will likely remain the symbology of choice indefinitely. Libraries, for example, have no compelling reason to change from Code 39 to a higher-density symbology. The book identifiers are short, label space is ample, and the installed base of scanners and software works reliably. The cost of change exceeds any benefit. |
Educational Value |
Beyond practical applications, Code 39 has significant educational value. Its simple encoding scheme makes it ideal for teaching barcode principles to students and practitioners. Many barcode software development kits use Code 39 as the default or example symbology because its encoding is straightforward to understand and implement. |
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Detailed Summary |
The 9-element pattern that defines Code 39---five bars and four spaces, three wide and six narrow---produces a symbology with a distinctive set of characteristics that have shaped its adoption across diverse industries. From the theoretical 84 possible combinations of three wide elements among nine, only 43 data characters plus the start/stop asterisk are used, yet this limited character set has proven remarkably useful in countless applications over five decades. |
The self-checking property, arising from the distinctiveness of each character's wide/narrow pattern, has been a key factor in Code 39's adoption in safety-critical applications such as military logistics, patient identification, and hazardous materials tracking. The ability to encode alphanumeric data, revolutionary in 1974, made Code 39 the first broadly useful barcode for non-retail applications and established its role in inventory management, asset tracking, and supply chain logistics across the automotive, manufacturing, healthcare, and defense industries. |
The LOW DATA DENSITY of Code 39, while a limitation that has driven many applications to adopt Code 128 or two-dimensional symbologies, has not prevented its continued use where data payloads are short and label space is adequate. The variable-length nature of the symbology provides flexibility, while the simple encoding allows generation with basic barcode fonts on ordinary printers---a practical advantage that has maintained Code 39's relevance in decentralized printing environments. |
The Full ASCII extension, while rarely used due to its density penalty, demonstrates the adaptability of the 9-element pattern to encode all 128 ASCII characters through two-character combinations. This extension has enabled Code 39 to serve applications requiring lowercase letters or extended punctuation, albeit at the cost of increased symbol length. |
The ubiquity of Code 39 support in scanners, printers, and software is perhaps its most enduring legacy. The installed base of Code 39 equipment and expertise is enormous, creating significant switching costs that have slowed the transition to newer symbologies. Even as Code 128 and two-dimensional codes have become the symbologies of choice for new applications, Code 39 persists in legacy systems, government logistics, library circulation, and industrial asset tracking. |
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Looking to the future, Code 39 will continue its gradual decline in new applications while maintaining its presence in legacy systems and niche applications where the cost of change exceeds any benefit. The symbology's 50-year history, from its invention by David Allais and Raymond Stevens in 1974 through its standardization in ANSI MH10.8M-1983 and ISO/IEC 16388, to its continued use in the modern era, is a testament to the durability of its simple yet effective 9-element design. |
The 9-element pattern, with exactly three wide elements out of nine, represents an elegant compromise between encoding capacity and decoding reliability. It has proven robust enough for military logistics, flexible enough for healthcare, simple enough for libraries, and ubiquitous enough to remain a practical choice for countless organizations worldwide. While technological progress continues to bring more efficient symbologies, the legacy of Code 39---and the 9-element pattern that defines it---remains deeply embedded in the infrastructure of global commerce and logistics. |
cs@easiersoft.com