Chapter 60: Final Verdict - The Honorable Pioneer | Summary in Brief | Code 39, often called Code 3 of 9, occupies a singular place in the history of automatic identification. It is the barcode that proved the technology could work outside the laboratory, on factory floors, in warehouses, and at retail counters around the world. Its design is not the most powerful, nor the most compact, nor the most feature-rich. But it is the most historically significant symbology in the non-retail world, and its influence reaches into almost every corner of modern logistics, manufacturing, healthcare, and government. This chapter serves as the final verdict on Code 39, examining its legacy through the lens of real-world applications across many industries. We will see that its technical characteristics, which are often described as limitations in comparison to newer codes, were precisely the features that made it so adaptable and trustworthy for decades. It is the Model T of barcodes: revolutionary, simple, and durable. And like the Model T, it was eventually superseded by faster, denser, and smarter designs that could carry more data in less space. That is the natural evolution of efficiency. But being superseded does not mean being forgotten, nor does it mean being obsolete. Code 39 remains in active use today, and its story is a masterclass in engineering trade-offs, practical problem-solving, and the enduring value of getting the basics right. | 
| The Origin of a Workhorse | To understand why Code 39 became so widespread, we must first understand the environment into which it was born. In the early 1970s, barcodes were a novelty. The Universal Product Code had been adopted for grocery checkout in 1973, but that system was designed for a very specific purpose: high-speed scanning of small, fixed-length numeric data on items that passed over a scanner in a controlled orientation. The UPC was brilliant for supermarkets, but it was nearly useless for manufacturing, inventory, and shipping. Those environments needed a barcode that could encode letters and numbers, could be printed on rough surfaces with low-quality equipment, could be read by human operators with handheld wands, and could be easily created without expensive phototypesetting machinery. Enter David Allais and Ray Stevens of Intermec, who developed Code 39 in 1974. Their goal was not to out-compete UPC but to serve a completely different market. They designed a barcode that was self-checking, meaning that every character was independently verifiable without needing a separate check digit. They designed it to use both wide and narrow bars and spaces, which made it tolerant of printing variations. They designed it with a start and stop character that was identical, so the code could be read in either direction. And they designed it to encode the full alphanumeric set: A through Z, 0 through 9, and seven special characters, plus the space character. That was enough for part numbers, serial numbers, job orders, and lot codes. The asterisk was chosen as the start/stop character, and it was never used as data, which gave Code 39 its distinctive look: every valid Code 39 symbol begins and ends with an asterisk. This simple design choice made it instantly recognizable to anyone who worked with barcodes. | 
| The technical heart of Code 39 is the pattern of five bars and four spaces that represent each character, with three of those nine elements being wide and the remaining six being narrow. That is why it is called Code 3 of 9. The wide elements are typically two to three times the width of the narrow elements, and this ratio is the key to its robustness. Because the scanner only needs to distinguish between wide and narrow, not measure exact widths, Code 39 can be printed on dot matrix printers, thermal printers, impact printers, and even hand-stamped metal plates. It can be read with laser scanners, CCD imagers, and even the oldest wand-style readers that require the operator to swipe the tip across the code. This tolerance is not a bug; it is a feature that no other symbology of that era could match. The self-checking nature comes from the fact that every character has exactly three wide elements, so if the scanner miscounts wide elements, it immediately knows an error has occurred. No check digit is strictly required, although many applications add one voluntarily. This simplicity meant that users could implement Code 39 without complex mathematics or special licensing fees. Intermec made the specification freely available, which was a radical decision at the time. They bet that widespread adoption would benefit their hardware sales more than licensing fees ever could. They were right. | 
| Yet this same simplicity carries inherent limitations. The most obvious is density. Because every character requires nine elements plus an intercharacter gap, Code 39 is quite long for its data content. Numeric-only strings are especially inefficient, since each digit takes up the same space as a letter. Compare that to Code 128, which can encode two digits in a single character, or the newer Data Matrix, which packs hundreds of characters into a tiny square. The second limitation is the lack of a mandatory check digit, which means that misreads, though rare, are not automatically detected unless the user adds a modulo 43 check digit or a custom checksum. The third limitation is the restricted character set: no lowercase letters, no punctuation beyond the seven specials, and no direct support for Unicode or binary data. In the 1970s and 1980s, these were not serious drawbacks. Part numbers were uppercase, serial numbers were numeric, and inventory codes used hyphens and periods. But as global supply chains expanded and data requirements grew more complex, these limitations began to chafe. Still, the installed base of Code 39 was so massive that it continued to thrive long after newer codes appeared. It is the classic example of 'good enough' being better than 'perfect.' | 
| Manufacturing: The Assembly Line Backbone | Now let us walk through the industries that built their identities around Code 39, starting with manufacturing. The factory floor is a harsh environment. Temperatures fluctuate, dust and oil coat surfaces, lighting is poor, and vibration is constant. Barcodes must survive on metal tags that are welded onto engine blocks, on paper labels that stick to shipping crates, and on plastic cards that hang from overhead conveyors. Code 39 excelled here because its wide-to-narrow ratio could be adjusted to suit the printing method. For example, a dot matrix printer with a worn ribbon could still produce a readable Code 39 if the wide bars were set to three times the narrow width. A thermal transfer printer with a dirty print head could still create a symbol with a 2.5-to-1 ratio. This adaptability meant that a single factory could use Code 39 on every work-in-process tag, from raw material receiving to final assembly. | Consider an automotive engine plant. Each engine block arrives as a rough casting with a metal plate attached. That plate is stamped with a Code 39 symbol encoding the casting lot number, the date of pour, and the alloy composition code. The stamping is done with a mechanical impact marker, which leaves a slight indentation. The bars are wide and narrow in relief, and the spaces are the unmarked metal. A handheld scanner, which is essentially a laser with a photodiode, reads this stamped code even after the engine has been painted, because the paint fills the indentations but the contrast between the raised wide bars and the recessed spaces remains detectable. As the engine moves through machining, each station scans the code to retrieve the process routing. A cylinder block might need different bore sizes depending on the alloy, and the scanner sends the code to a central database that returns the correct tool settings. No other barcode of that period could tolerate the combination of metal stamping, high heat, and oily residue. Code 39 did it without fail. | 
| In aerospace manufacturing, where traceability is not optional but legally mandated, Code 39 was the standard for decades. Every turbine blade, every landing gear component, every fastener has a unique serial number. These are often marked with dot peen or laser etching directly onto the titanium or aluminum surface. The marks are shallow, and the contrast is low, but Code 39's binary decision between wide and narrow gives it an advantage over codes that require precise edge detection. A laser-etched Code 39 might have bars that are only a few thousandths of an inch deep, yet a properly tuned scanner can still read it because the algorithm is looking for ratios, not absolute reflectivity. This is the same reason that Code 39 was used on printed circuit boards, where the barcode is often placed on the solder mask next to components. The mask is green or blue, the copper underneath is gold or silver, and the contrast is mediocre at best. But Code 39 does not care. It just needs to see wide bars that are roughly two to three times the width of narrow bars. That tolerance is what made it the default for the electronics industry until the mid-1990s. | The manufacturing industry also loved Code 39 for its human readability. The asterisk start and stop characters are printed in the human-readable interpretation below the barcode, so operators can visually confirm the data without scanning. This might seem trivial, but on a busy assembly line, a supervisor can glance at a tag and read the part number directly if the scanner fails or the label is smudged. Newer 2D codes do not offer this convenience; they look like random patterns of black and white squares, and humans cannot decode them without a camera. Code 39, in contrast, is a bridge between machine and human readability. That dual nature was essential for training new employees and for manual fallback procedures. Even today, many manufacturing execution systems retain Code 39 as a backup symbology, even if their primary labels now use Code 128 or Data Matrix. | 
| Warehousing and Logistics: The Sorting Yard Standard | Moving from the factory to the warehouse, Code 39 found its second great domain. Warehousing is about moving boxes, pallets, and totes from receiving docks to storage racks to shipping bays. The barcode is printed on corrugated cardboard, often with large-format inkjet printers that have coarse resolution. The labels are exposed to forklift exhaust, rain, and abrasion from other boxes. The lighting in a warehouse is typically high bay fluorescent, which has flicker and uneven coverage. And the scanners are often handheld pistol-grip units that operators use hundreds of times per shift. In this setting, Code 39's length, which we earlier called a limitation, actually becomes an advantage for another reason: it is very easy to scan at a distance. The wide bars provide large reflective surfaces that return a strong signal to the laser scanner. A Code 39 label that is six inches long can be read from three feet away, whereas a denser code of the same data length might be only two inches long and require the operator to move closer. In a busy receiving area, that extra reach saves seconds per scan, and seconds accumulate into hours over a shift. | Consider a third-party logistics provider that handles apparel for a major retailer. Each carton of shirts arrives from a different overseas factory. The carton label carries a Code 39 symbol that encodes the purchase order number, the style code, the color code, and the size. This is typically 12 to 15 characters. The receiving clerk scans the label with a wireless laser scanner, and the warehouse management system immediately routes the carton to a specific aisle and bay. The label also carries a separate Code 39 for the carton serial number, which is used for tracking through the putaway process. The operator does not need to orient the label perfectly; Code 39 is omnidirectional in the sense that it can be read from left to right or right to left because the start and stop asterisks are identical. This bidirectional reading capability is a direct result of the design choice to use the same character for both ends. If the operator scans the label upside down, the data comes out reversed, but the scanner's firmware detects the start/stop pattern and reverses the string automatically. That seamless handling reduces training time and error rates. | 
| In cross-dock operations, where products are unloaded from incoming trailers and immediately loaded onto outgoing trailers with minimal storage, speed is everything. Code 39 labels are pre-printed on shipping documents and pasted onto the top or side of each pallet. The pallets are moved on conveyor belts past fixed-mount scanners that read the labels at high speed. The fixed scanners are often laser arrays that sweep a beam across the pallet as it moves. Code 39's wide bars produce a strong pulse that triggers the decoding logic easily, even when the label is slightly curved around a corner of the carton or obscured by stretch wrap. Stretch wrap is a notorious problem for barcodes because the plastic film reflects light in unpredictable ways, creating glare and diffused reflections. Code 39, with its large element widths, is more tolerant of this than dense codes like Code 128, which require precise measurement of narrow bars. Many warehouse operators still choose Code 39 for master carton labels specifically for this reason, even though they might use Code 128 for inner pack labels. The trade-off is accepted because the reliability in poor conditions is more valuable than the space savings. | Another logistics application that made Code 39 famous is the tracking of returnable assets. Pallets, drums, gas cylinders, and shipping containers are expensive items that circulate between suppliers and customers. They are often marked with Code 39 on metal tags or plastic plaques that are riveted to the asset. These tags must survive outdoor weather, chemical washes, and repeated impacts. Code 39 stamped into a metal tag is almost indestructible. The wide bars are deep impressions, and the narrow bars are shallower. A handheld scanner with a long-wavelength red laser can read the differential depth even when the tag is covered in mud or rust. This is not theoretical; it has been proven in the oil and gas industry, where drill pipes are tracked with Code 39 tags throughout their service life, which can span decades and multiple continents. The same tag that was stamped in Texas can be read in the North Sea or the Persian Gulf, using the same basic decoding algorithm. That consistency is the bedrock of asset management. | 
| Healthcare: Patient Safety and Specimen Tracking | Healthcare is an industry where errors have life-or-death consequences, and Code 39 played a pivotal role in the early adoption of barcode-based patient identification. In the 1980s and 1990s, hospitals began using wristbands with Code 39 labels that encoded the patient's medical record number, date of birth, and sometimes a unique encounter number. The wristband was printed on a thermal printer at the admissions desk and placed on the patient's wrist. Nurses would scan the wristband before administering medication, drawing blood, or performing a procedure. The scanner would then verify that the patient matched the order in the electronic medical record. This simple check reduced medication errors dramatically, because it forced a positive patient identification before any action. | The technical reasons for choosing Code 39 in healthcare are instructive. First, the wristband is curved around a small wrist, and the label must conform to the curvature without cracking. Code 39 labels are typically printed on flexible polyester or vinyl, and the relatively large bar widths mean that the label does not need to be folded into tiny spaces. Second, the wristband might be exposed to water, alcohol, blood, and bodily fluids. Code 39 printed with a thermal ribbon on a synthetic stock holds up well because the black coating is part of the material, not just on the surface. Third, hospital scanners are often handheld with a trigger, and nurses are constantly moving between rooms. They need a code that can be read quickly without precise aiming. Code 39's forgiving depth of field and wide bars make it easy to scan from a few inches away even if the scanner is tilted. Fourth, the human-readable text on the wristband is crucial because clinicians often double-check the name and date of birth visually before scanning. The asterisk-bounded text provides a clear visual cue that the barcode is a Code 39 symbol, which reduces confusion with other barcodes that might appear on the patient's chart or medication vial. | 
| Blood banks adopted Code 39 for labeling blood bags, which are flexible plastic pouches that are stored in refrigerated conditions. Each bag carries a unique donor number and blood type encoded in Code 39. The label must withstand freezing, thawing, and exposure to moisture. Code 39 printed with a specialized ink that adheres to plastic works reliably. The scanners used in blood banks are often stationary units that the technologist passes the bag over. The bag is curved and the label is on a floppy surface, but Code 39's large element size ensures that even with slight defocusing, the wide and narrow bars remain distinguishable. When the blood is transfused to a patient, the nurse scans both the patient's wristband and the blood bag label to confirm compatibility. This dual-scan process, known as bedside verification, became the standard of care in many countries, and Code 39 was the enabler of that protocol. Although many hospitals have since transitioned to Code 128 or GS1 DataBar for their improved data capacity and error detection, Code 39 is still found in legacy systems and backup procedures. It is not uncommon to see a modern hospital using a hybrid approach: new labels are printed with Code 128, but old wristbands from long-term patients remain with Code 39, and the scanners are configured to read both. | In pathology and laboratory testing, Code 39 labels are affixed to specimen tubes, slides, and culture plates. These labels are often small, because the tubes are narrow, but Code 39 can be printed in a compressed format by reducing the narrow bar width to as little as 0.010 inches. At that size, a 10-character code becomes about 1.5 inches long, which fits on a standard 13-millimeter tube. The laboratory information system assigns a unique accession number to each specimen, and that number is encoded in Code 39. The lab technician scans the tube before loading it onto an analyzer, which retrieves the test orders. This ensures that the correct tests are performed on the correct specimen, eliminating mix-ups that could lead to misdiagnosis. The tolerance of Code 39 to poor printing is especially valuable here, because the tube labels are often printed on-demand by a small thermal printer that sits next to the phlebotomist. The printer might not be perfectly calibrated, and the label might be slightly skewed on the tube, but Code 39 decodes anyway. Newer 2D codes like Data Matrix would require higher resolution and better contrast, which is why many laboratories still default to Code 39 for routine specimen labeling, reserving 2D codes for high-density applications like microtiter plates. | 
| Government and Defense: The Tracking of Assets and Personnel | Government agencies and military organizations are notoriously conservative in technology adoption, which made Code 39 a perfect fit. In the United States, the Department of Defense adopted Code 39 as the standard for item identification in the early 1980s under the LOGMARS program (Logistics Applications of Automated Marking and Reading Symbols). This program mandated that all supplies shipped to the military carry a Code 39 label with the National Stock Number, the quantity, the unit of issue, and the contract number. The requirement applied to everything from a single bolt to a tank engine. This single decision created a tidal wave of Code 39 adoption among defense contractors, who had to retrofit their labeling systems to comply. The LOGMARS standard specified a specific wide-to-narrow ratio of 2.5 to 3.0, a minimum height of 0.25 inches, and a quiet zone of at least 10 times the narrow bar width. These specifications were designed to ensure readability across the entire supply chain, from the contractor's factory to the forward operating base. | The technical reasoning behind the LOGMARS choice is worth examining. The military needed a code that could be printed by a wide variety of means: offset lithography for large cartons, direct thermal for field-deployable printers, and impact printing for metal tags. No other symbology at that time offered such flexibility. The military also required that the code be readable with handheld wand scanners that soldiers could use in the field, where electricity and lighting were unreliable. Code 39's robust wide/narrow discrimination meant that a simple wand scanner with a single LED and phototransistor could decode the symbol without complex signal processing. This was crucial for logistics operations in the field, where heavy, expensive imaging scanners were not feasible. Moreover, the military valued the error-detection capability of the modulo 43 check digit, which was optional but recommended. This check digit added one character to the data, increasing the symbol length, but the military accepted that trade-off for improved reliability. | 
| Another prominent government use was the U.S. Postal Service's adoption of Code 39 for mail tracking in the 1980s. They used a variant called POSTNET (Postal Numeric Encoding Technique) which was actually a different symbology, but many of their internal sorting labels used Code 39 for tray and container identification. The postal environment is demanding because mailpieces are moving at high speeds on conveyors, and the labels must be read in fractions of a second. Code 39's simple wide/narrow logic allowed for very fast decoding with the hardware of that era. A laser scanner could sweep across a label and, within a few milliseconds, count the wide elements in each character to produce the decoded data. This was much faster than the more computationally intensive algorithms required for Code 128, which uses variable-length characters and multiple element widths. Speed was the decisive factor for postal automation, and Code 39 delivered. | In law enforcement and forensics, Code 39 was adopted for evidence tracking. Every item collected from a crime scene is assigned a unique evidence number, and that number is encoded in a Code 39 label that is placed on the evidence bag. The chain of custody is recorded by scanning the label each time the evidence is transferred from one person or location to another. The labels are often printed on tamper-evident stock, which shows signs of removal if someone tries to peel it off. Code 39's large size makes the label easy to locate on a crowded evidence shelf, and the human-readable text allows investigators to quickly identify items without powering on a scanner. In courtrooms, the human-readable portion of the label is often photographed and entered into evidence, and the barcode itself provides a secondary means of verification. This dual-use aspect is something that newer, denser codes cannot match, because their human-readable component is either omitted or printed in a tiny font that is not easily legible. | 
| Retail and Point-of-Sale: The Unlikely Niche | Although Code 39 was not designed for supermarket checkout, it found a significant niche in retail for non-grocery items that required more than numeric data. Department stores, jewelry shops, and electronics retailers used Code 39 to encode internal stock-keeping unit (SKU) numbers that included letters and dashes. These labels were often printed in-store on electronic shelf labeling systems or on price tags attached to clothing. The advantage over UPC was that the merchant could create meaningful codes, such as 'SHIRT-RED-M' for a red medium shirt, instead of a cryptic 12-digit number. This made inventory management easier for staff who did not have access to the central database. They could look at a rack of shirts, read the human-readable Code 39 text, and know instantly what was in stock. The barcode itself was used at the point of sale when the cashier scanned the tag to ring up the sale. The register would then look up the price from a local file that mapped the code to the current price. This was common in the 1980s and 1990s before the universal adoption of UPC-A for all retail items. | Another retail application was in library circulation. Libraries were early adopters of barcode technology, and Code 39 was the standard for book labels for many years. Each book received a label with a Code 39 symbol encoding the book's unique accession number or barcode ID. The labels were often printed on acid-free paper and laminated to protect against wear. Library patrons would bring books to a self-checkout station, where a fixed scanner would read the Code 39 label and record the loan. The large size of Code 39 made it easy for patrons to align the book correctly, and the bidirectional reading meant they did not need to orient the book in a particular direction. Librarians appreciated the human-readable digits beneath the barcode, which allowed them to manually check in books if the scanner failed. Even today, many public libraries still use Code 39, although newer systems have migrated to Code 128 or even RFID tags. But the legacy of Code 39 in libraries is so strong that it is still the default for many integrated library systems. | The retail industry also used Code 39 for gift cards and loyalty cards. The card would have a magnetic stripe for electronic transactions, but the barcode was printed on the back as a backup. Code 39 was chosen because it could be printed on plastic cards using thermal transfer or even embossing, and it could be read by low-cost laser scanners at the register. The data encoded was typically the card number and a check digit. When a customer presented the card, the cashier scanned the barcode to look up the balance or loyalty points. The robustness of Code 39 to scratches and scuffs was a major advantage, because plastic cards are constantly rubbed against wallets, keys, and counters. A scratched UPC or Code 128 might become unreadable, but a scratched Code 39 often remains decodable because the wide elements are broad enough that a scratch across a portion of the bar does not eliminate the entire signal. This resilience is not often discussed in technical specifications, but it is a practical benefit that retail workers came to rely upon. | 
| Transportation and Airlines: Boarding Passes and Baggage Tags | The airline industry was another early adopter of Code 39, specifically for baggage tracking and boarding passes. In the 1980s, airlines began printing luggage tags with Code 39 symbols that encoded the flight number, destination airport code, and passenger name. These tags were attached to each checked bag and were read by handheld scanners at check-in counters and by fixed scanners on baggage conveyor systems. The reading distance was critical because the bags were moving at high speeds through a sorting labyrinth. Code 39's large module size allowed the scanners to read the tag from up to four feet away, even if the tag was partially folded or obscured by the bag's handle. The tags were printed on adhesive paper with a thermal transfer printer, and the ink was resistant to smudging from rain and grease. The airlines also used Code 39 on boarding passes, which were printed on thermal paper at the check-in kiosk. The boarding pass contained the passenger's record locator and seat assignment, and the gate agent scanned it to validate boarding. The readability of Code 39 from various angles was essential because passengers would present their boarding passes in all orientations, and the gate agent needed to scan them quickly to maintain boarding efficiency. | In the air cargo sector, Code 39 was used on air waybills and package labels. Each shipment received a unique air waybill number, which was encoded in Code 39 and printed on the label attached to the freight. The cargo handlers would scan the label at each transfer point: from the truck to the warehouse, from the warehouse to the aircraft, and from the aircraft to the destination warehouse. This provided end-to-end visibility for high-value or time-sensitive shipments. The tolerance of Code 39 to low contrast was valuable here because the labels were often printed on brown kraft paper or on recycled cardboard, which had a low reflectivity. A laser scanner with a red beam could still pick out the wide bars from the narrow spaces because the differences in width created a distinct pulse pattern. Newer codes that rely on high contrast sometimes struggle on such substrates, but Code 39 works reliably even when the reflectance difference is as low as 20 percent. That is a testament to the wisdom of the original design. | 
| Utilities and Energy: Remote Meter Reading and Asset Tagging | Utility companies, including electric, gas, and water providers, have used Code 39 for asset identification and meter reading. Each utility meter, whether it measures electricity consumption or water flow, is assigned a unique serial number. That serial number is often encoded in a Code 39 label that is affixed to the meter housing. The meter reader, who might be walking through a neighborhood, uses a handheld laser scanner to capture the Code 39 label without having to remove the meter cover. The label is designed to be readable from a distance of two to three feet, which allows the reader to scan it from a safe standing position. The outdoor environment subjects the label to sunlight, rain, snow, and extreme temperatures. Code 39 printed on a durable polyester label with a UV-resistant overlaminate can last for decades without fading or cracking. The wide bars provide a larger target for the scanner, which is helpful when the meter is in a shadow or the reader is wearing gloves and cannot fine-aim the device. | In the oil and gas industry, pipelines and wellheads are tagged with Code 39 plates to identify their location, construction date, and maintenance history. These plates are often welded onto the infrastructure and must survive harsh chemical exposure and mechanical stress. Code 39 is sometimes etched into stainless steel using a laser, creating a permanent mark that will not corrode or peel. The mark has a dark oxidized appearance against the shiny metal, providing the necessary contrast. The wide bars are clearly distinguishable from the narrow ones under magnification, and a specialized scanner with a blue or green laser can read the mark even if it is partly covered by dirt. This application is a perfect example of how Code 39's simplicity translates into longevity. There are gas pipelines in operation today that were tagged with Code 39 in the 1980s, and those tags are still readable. The same cannot be said for many early 2D codes, which were printed on labels that have since deteriorated. | Telecommunications companies used Code 39 for labeling fiber optic cables and junction boxes. Each cable segment has a unique identifier that encodes the cable type, the number of fibers, and the installation route. The labels are small, often no more than one inch by two inches, and they are attached to the cables with a tie wrap. The limited space would seem to favor a denser code, but Code 39 was chosen because the labels are often read in the field under poor lighting, sometimes with a headlamp or flashlight. The human-readable portion is critical here because technicians need to visually confirm the cable identifier before making a splice. The Code 39 barcode serves as a machine-verifiable backup that reduces transcription errors. Even as telecommunications networks have upgraded to more sophisticated inventory systems, many field crews still rely on Code 39 because their handheld scanners are programmed to decode it first, and they have developed muscle memory for scanning that specific symbology. | 
| Automotive Aftermarket and Parts Distribution | The automotive aftermarket, which includes replacement parts sold to repair shops and consumers, is a massive ecosystem where Code 39 remains dominant. Every part from a starter motor to a brake caliper has a part number that often includes letters and dashes, such as 'A123-456-B'. That exact part number is encoded in a Code 39 label that is printed on the packaging. The parts distributor scans the label during receiving, putaway, picking, and shipping. The warehouse management system uses the part number to locate the item in the bin and to update inventory counts. The reason Code 39 persists in this industry is the sheer variety of legacy systems. Many of the large parts distributors installed their first barcode systems in the late 1980s, and those systems were built around Code 39. They have since upgraded hardware and software, but the labels remained Code 39 because changing the label format would require reprinting millions of existing packages and retraining thousands of employees. The cost of migration is simply too high, especially when the existing system works adequately. | Moreover, the parts themselves often have the part number stamped directly onto the metal using dot peen or engraving. The automotive industry has standardized on Code 39 for direct part marking because the stamping process is mature and well-understood. A dot peen machine creates a series of small dots that form wide and narrow bars. The wide bars are made by spacing the dots closely together, while the narrow bars are made by spacing them farther apart. The spaces between bars are left unmarked. A reader with a camera and appropriate lighting can decode this pattern, and the decoding algorithm is the same as for printed labels. This consistency across marking methods is a unique advantage of Code 39. Other codes, especially 2D matrix codes, require a grid of precisely placed modules, which is harder to achieve with dot peen without special tooling. Code 39's linear nature makes it naturally suited to single-axis marking, which is cheaper and faster. Therefore, you will find Code 39 on millions of automotive parts that are manufactured every year, from alternators to suspension arms. | 
| Aerospace and Defense, Continued: The Reliability Imperative | We already touched on aerospace earlier, but it deserves a deeper look because the industry's requirements are so stringent. In aviation, every component must be traceable from its raw material batch to the final aircraft assembly. The Federal Aviation Administration and its equivalents around the world require that parts be marked with a permanent identification that includes the manufacturer's code, the part number, and the serial number. Code 39 was the first symbology to be accepted for this purpose, and it is still widely used even though newer standards like the UID (Unique Identification) have mandated Data Matrix for certain military contracts. The reason for Code 39's longevity in commercial aerospace is the installed base of readers. Airline maintenance hangars have hundreds of handheld scanners that were purchased over two decades. Those scanners decode Code 39 natively and reliably. Replacing them with 2D imagers would cost millions of dollars, not to mention the software updates and training. So airlines continue to use Code 39 for their internal maintenance tracking, even as the original equipment manufacturers have moved to 2D codes for new production. | One specific application is the tracking of life-limited parts, such as turbine disks and landing gear components. These parts have a fixed number of flight cycles or hours of operation, after which they must be retired. The Code 39 serial number is used to log every installation, removal, inspection, and repair. The label is often embedded in a metal tag that is riveted to the part, so it cannot be lost. The tag is designed to withstand the heat of a turbine engine or the hydraulic fluid of a landing gear bay. The Code 39 symbol is relatively large, which is acceptable because the parts themselves are large. The scanner used in the hangar is a ruggedized model with a long cord or wireless connectivity. The operator scans the tag before removing the part, and the system records the removal against the aircraft tail number. This creates a complete history that is audited by regulators. The simplicity of Code 39 means that even if the database is temporarily offline, the operator can read the human-readable serial number and write it down manually, ensuring that the physical work can continue. That redundancy is not a design feature but a fortunate consequence of the symbology's human-readable format. | 
| Security and Access Control | Code 39 has also been used in security badges and access control cards. Many corporate ID cards have a Code 39 barcode printed on the back that encodes the employee ID number. The card holder presents the badge to a reader at a door, and the reader scans the barcode to verify the employee's access rights. This was particularly popular in the 1990s before smart cards and RFID became inexpensive. The barcode reader is a simple laser scanner embedded in the wall, and the scanning distance is a few inches. Code 39 was chosen because it can be printed on PVC cards using standard card printers, which are essentially thermal printers with a ribbon. The black bars are crisp and durable, and they do not fade over time. The wide/narrow ratio is easily controlled by the printer driver. The cards are used daily, swiped through the reader, and they endure wear from wallets and purses. Code 39 holds up well because the bars are broad enough that minor scuffs do not destroy the pattern. | In government buildings and military installations, Code 39 is sometimes used for visitor passes. The pass includes a temporary access code that is valid for one day. The guard at the entrance scans the Code 39 to validate the code against the visitor management system. If the code is valid, the guard prints a second label with the same code and attaches it to the visitor's badge. This dual-label system ensures that the visitor's badge matches the entry log. The human readability of Code 39 allows the guard to quickly compare the printed code on the badge with the code on the visitor's ID, adding a layer of visual verification that a purely machine-readable code would not provide. This combination of machine and human verification is something that security professionals value, because it reduces the risk of a false positive or a misread that could allow unauthorized entry. | 
| Pharmaceutical and Medical Device Manufacturing | The pharmaceutical industry adopted Code 39 for unit-of-use labeling on vials, ampoules, and blister packs. Each package contains a lot number and expiration date, which are encoded in Code 39 alongside the product code. The manufacturing process requires that each batch be tracked through filling, capping, labeling, and packaging. Code 39 labels are printed at high speed on a rotary labeler and applied to the vials as they move along a conveyor. The labels are small, but the data is also short, typically 8 to 12 characters. The barcode is read by a verification camera immediately after application to ensure that the label matches the product and that the print quality is acceptable. If the verification fails, the vial is rejected automatically. Code 39's simple structure makes it easy for the verification system to perform a quality assessment based on the ratio of wide to narrow bars. The system can measure the average bar width and the standard deviation, and it can reject labels that do not meet the specified ratio. This quality control is essential in pharmaceuticals, where mislabeling can lead to patient harm. | Medical device manufacturers also use Code 39 for tracking instruments that are sterilized and reused, such as surgical forceps, endoscopes, and saws. Each instrument is etched with a Code 39 symbol that encodes a unique device identifier. The instrument goes through a sterilization cycle after each use, which involves high temperatures, steam, and chemical disinfectants. The Code 39 etching must withstand this aggressive environment. Many medical devices are made of stainless steel or titanium, and the etching is done with a fiber laser that creates a dark, permanent mark. The mark is readable even after hundreds of sterilization cycles, because the wide bars are deep enough to retain contrast. The hospital's sterile processing department scans the Code 39 before and after each cycle to track the number of uses and to ensure that the instrument is not nearing its end of life. This practice has been credited with reducing surgical errors and improving patient outcomes. Although newer standards like UDI (Unique Device Identification) allow for Data Matrix and GS1-128, Code 39 remains a common choice for legacy instruments and for institutions that have not yet upgraded their scanning infrastructure. | 
| Agriculture and Food Processing | The agriculture and food processing industry uses Code 39 for traceability from farm to fork. A crate of produce, such as apples or lettuce, is labeled with a Code 39 symbol that encodes the grower's lot number, the harvest date, and the field location. This label is applied in the field using a portable printer, and it remains on the crate throughout transportation, cold storage, and distribution. If a food safety issue arises, such as a contamination outbreak, the distributor can scan the Code 39 labels to quickly identify which crates came from which field and which lot. This rapid traceability is essential for limiting the scope of recalls and for protecting public health. The Code 39 label is printed on water-resistant paper that can be frozen or washed. The wide bars are large enough that they do not bleed or smudge when the label gets wet. The cold storage environment, which can be near freezing, does not affect the readability because the thermal transfer ink remains solid and stable. Handheld scanners used in cold rooms are often designed with rubber grips and heated elements, but the barcode itself requires no special treatment. | In meat processing, Code 39 is used on boxes of carcasses and cuts. Each box carries a code that identifies the slaughterhouse, the date, the weight, and the quality grade. The labels are applied in a wet and bloody environment, so they must be resistant to moisture and abrasion. Code 39 printed on a synthetic label with a high-tack adhesive stays adhered even when the box is stacked under heavy loads. The scanning is performed by workers wearing gloves and hairnets, using handheld scanners that are enclosed in protective boots to prevent contamination. The decoding reliability of Code 39 is crucial because a misread could send the wrong cut of meat to a customer, leading to customer complaints or even health code violations. The simplicity of the symbology means that the scanners can be low-cost and maintenance-free, which is important in an industry with narrow profit margins. | 
| Shipping and Courier Services | Every major courier service has used Code 39 at some point in its history. For example, the United States Postal Service, as mentioned earlier, used Code 39 for tray labels. Private couriers like FedEx and UPS also employed Code 39 for their internal sortation labels before moving to proprietary symbologies. The reason was the same as in other industries: reliability, printing flexibility, and human readability. A courier label typically contains a tracking number of 10 to 20 digits, plus a service code and a destination zip code. Code 39 can encode all that in a single symbol, although the resulting label is quite long, often 4 to 6 inches. That length is not a problem on a large shipping label, which is often 6 inches by 8 inches. The courier's automated sorting machines use laser scanners that read the Code 39 label as the package travels down a conveyor at high speed. The scanners are mounted overhead and on the sides, and they read the label from multiple angles. Code 39's bidirectional reading capability allows the machine to decode the label regardless of whether the package is facing forward or backward on the conveyor. This reduces the need for manual orientation, which speeds up the sorting process. | When a package is delivered, the driver often scans the Code 39 label with a handheld mobile computer to confirm the delivery. The device is carried throughout the day, exposed to rain, heat, and drops. Code 39 labels on the packages are sometimes crumpled or torn, but the driver can still scan the intact portion because the data is not spread across a large area. The redundancy of the Code 39 structure, with its start and stop asterisks, means that even if the first or last character is damaged, the scanner can often reconstruct the data from the remaining characters. This is not always true for codes that rely on a fixed number of characters, but Code 39's self-checking nature and simple start/stop markers provide a degree of error correction through redundancy. Many couriers have since moved to 2D barcodes that hold more data and support advanced error correction, but they still retain Code 39 as a fallback for legacy customers and for labels that are printed in remote locations where high-resolution printers are not available. | 
| The Inevitable Supersedure: Why Newer Codes Won | Despite all these strengths, Code 39 could not hold the top position forever. The quest for efficiency is relentless, and the limitations of Code 39 became more glaring as data requirements grew. The most obvious limitation is the low information density. A Code 39 label for a 20-character alphanumeric string is about 4 inches long at a typical narrow bar width of 0.015 inches. That same string encoded in Code 128 is about 2.5 inches long, and in Data Matrix it is a tiny square of less than 0.5 inches. This matters when labels must fit on small electronic components, pharmaceutical vials, or surgical instruments. It also matters for printing cost, because a smaller label uses less ink and less material. The second major limitation is the lack of built-in error correction. Code 39 has a self-checking feature at the character level, but if the entire symbol is partially damaged, the data might be lost. Code 128 has a mandatory check digit, which catches most single errors. Data Matrix and QR Code have Reed-Solomon error correction that can recover the data even if up to 30 percent of the symbol is destroyed. This is a game-changer for industrial environments where labels are frequently scratched or covered in dirt. | The third limitation is the restricted character set. As global trade expanded, companies needed to encode product identifiers that contained lowercase letters, accents, and even Unicode characters. Code 39 cannot handle these. It also cannot encode binary data, such as a JPEG image or a cryptographic signature. Newer codes support full ASCII, ISO-8859, and UTF-8, making them suitable for modern applications like electronic health records and digital certificates. The fourth limitation is the lack of a standardized global data structure. Code 39 is a 'generic' symbology; it does not enforce any particular format for the data. This meant that different companies used different conventions for separating fields, leading to interoperability issues. GS1 solved this by defining Application Identifiers for Code 128 (and later for Data Matrix) so that the same label could be read by any GS1-compliant scanner and interpreted correctly. Code 39 never had such a universal standard, although some industries developed their own local conventions. The final nail in the coffin was the advent of 2D imagers, which are now cheaper and faster than laser scanners. These imagers can read any symbology with the same hardware, removing the cost advantage that laser scanners had for Code 39. With imagers, there is no reason to stick with a low-density code when you can print a high-density 2D code and achieve much greater reliability and data capacity. | Efficiency drove the evolution. Code 128, introduced in 1981, offered double the density of Code 39 and a richer character set. It became the standard for shipping and logistics in the 1990s. Then came Data Matrix in 1994, which could encode 50 characters in a space smaller than a dime. The electronics and healthcare industries quickly adopted it for marking tiny components. Then came QR Code in 1994 as well, which was designed for fast reading by cameras and for consumer-facing applications. Each new code represented a leap forward in efficiency, and each leap made Code 39 look more like a dinosaur. But we must remember that dinosaurs ruled the Earth for hundreds of millions of years. Code 39 has ruled the non-retail barcode world for nearly five decades, and it is still not extinct. | 
| The Enduring Legacy: Why Code 39 Survives | To call Code 39 obsolete would be a gross misrepresentation. It is still manufactured in billions of labels every year, still scanned millions of times per day, and still taught in introductory courses on barcode technology. Its survival can be attributed to several key factors. First, there is the immense installed base of scanners and printers that are specifically optimized for Code 39. These devices are already paid for, and they work reliably. Replacing them would require a capital expenditure that many companies are unwilling to make, especially when the current system meets their needs. Second, there is the human readability. No other barcode offers such a clear and easy-to-read human interpretation that is also machine-decodeable. For applications where people need to interact with the code visually, Code 39 remains unmatched. Third, there is the simplicity of the specification. You can write a Code 39 decoder in a few dozen lines of code, and you can generate a Code 39 label with any graphics library that supports vector drawing. This low barrier to entry makes Code 39 the go-to choice for hobbyists, small businesses, and prototyping projects. | Fourth, there are the regulatory and legacy systems. Many government standards, such as the U.S. Department of Defense's MIL-STD-130 and various FAA regulations, still list Code 39 as an approved marking method. Changing these regulations is a slow, bureaucratic process that takes years. Until they are revised, contractors must comply, which means they continue to use Code 39. Fifth, there is the tolerance to difficult printing conditions. For applications that use dot matrix, impact, or low-quality thermal printers, Code 39 often outperforms Code 128 because the wide/narrow discrimination is easier to achieve than the precise edge positioning required by more complex codes. Sixth, there is the psychological comfort factor. Generations of engineers, technicians, and logisticians grew up with Code 39. They trust it. They know its quirks. They have decades of experience troubleshooting printing and scanning issues. This institutional knowledge is a form of capital that is not easily discarded. | 
| The Final Verdict: An Honorable Pioneer | So, is Code 39 a symbol of backwardness or a testament to enduring engineeringThe answer, as with most things, is nuanced. Code 39 is a brilliant example of a design that perfectly matched the needs of its era. It solved the problem of machine-readable, human-readable, flexible, error-tolerant labeling for manufacturing, logistics, healthcare, and government. It was not the fastest or the smallest, but it was the most practical and the most democratic. Intermec's decision to release it without licensing fees was a philanthropic move that accelerated the adoption of barcode technology across all industries. We owe Code 39 a debt of gratitude for proving that automatic identification could work in the real world, not just in pristine labs. Without Code 39, the barcode revolution might have been delayed by a decade, and the efficiencies we enjoy today might not exist. | But progress is defined by succession. The Model T gave way to the Model A, then to the V-8, then to the Mustang, and finally to the electric vehicles of today. Each generation was superior in speed, comfort, and efficiency. Yet we do not laugh at the Model T; we honor it as the first automobile that brought mobility to the masses. Similarly, we must honor Code 39 as the first barcode that brought automated data collection to the factories, warehouses, hospitals, and battlefields of the world. Its technical characteristics, which we have dissected in this book, are not flaws but features that served a specific purpose at a specific time. The wide bars, the long symbols, the lack of a built-in check digit, the restricted alphabet - these were all compromises made to achieve robustness, printability, and simplicity. They were the right compromises for the 1970s and 1980s, and they remain acceptable for many applications today. | 
| As we look to the future, Code 39 will not disappear. It will slowly cede ground to denser, smarter symbologies, but it will continue to occupy a comfortable niche. You will find it on older assets, on backup labels, on internal tracking systems, and on any application where human readability and printing ease are more important than data density. You will find it in textbooks, in training manuals, and in the fond memories of engineers who cut their teeth on barcode technology. It is a pioneer, and pioneers never truly retire; they simply become the foundation upon which newer structures are built. In that sense, Code 39 is immortal. Every time a laser scanner decodes a Code 128 or a camera decodes a Data Matrix, the algorithms used are descendants of the wide/narrow logic that Code 39 pioneered. The concept of a start/stop character, of self-checking, of encoding multiple character sets using a simple pattern - these are all legacies of Code 39. | Let us, therefore, render the final verdict. Code 39 is not the best barcode, nor the most modern, nor the most efficient. It is the most honorable. It was there when we needed it most. It did not ask for royalties. It did not require complex firmware. It did not need high-resolution cameras or supercomputers. It worked with a simple wand and a simple printer. It gave us the confidence to trust machine-readable labels, and that confidence opened the floodgates for all subsequent innovations. In the grand arc of technology, the pioneers are often overshadowed by the successors, but their contributions are never forgotten. Code 39 will be remembered as the workhorse that carried the burden of early automation, and its legacy will live on in every barcode that follows. | 
| Detailed Summary of Code 39's Industrial Impact | Let us now consolidate all the industry examples we have covered and map them to specific technical characteristics. This summary is organized by application domain and technical attribute, so you can see the direct connection between what Code 39 is and how it is used. | 1. Manufacturing and Heavy Industry | - Application: Work-in-process tracking, engine block marking, turbine blade serialization. | - Key Technical Characteristics: Tolerance to low-contrast and rough surfaces (metal stamping, laser etching); wide/narrow ratio adjustable for impact printing; large element size for long reading distances; bidirectional reading for flexible orientation; human-readable fallback for manual verification. | - Real-World Outcome: Decades of reliable tracking in automotive, aerospace, and electronics manufacturing, enabling just-in-time production and component traceability. |
| 2. Warehousing and Logistics | - Application: Carton labeling, pallet tracking, cross-dock sortation, returnable asset management. | - Key Technical Characteristics: Strong signal return from wide bars; forgiveness of curvature and stretch wrap; readability on corrugated cardboard with coarse printing; bidirectional scanning for high-speed conveyor reading; resistance to smudging and moisture. | - Real-World Outcome: Widespread adoption in third-party logistics, retail distribution, and parcel shipping, with many systems still using Code 39 for master carton labels. |
| 3. Healthcare and Medical | - Application: Patient wristbands, blood bag labels, specimen tubes, surgical instrument tracking. | - Key Technical Characteristics: Flexibility to print on curved, flexible surfaces; resistance to alcohol, water, and sterilization heat; human-readable text for visual double-check; tolerance to low-quality thermal printers; self-checking for error reduction. | - Real-World Outcome: Significant reduction in medication errors and specimen mix-ups; established as the standard for bedside verification and blood bank traceability for over two decades. |
| 4. Government and Military | - Application: LOGMARS item identification, postal tray labels, evidence tracking, property accountability. | - Key Technical Characteristics: Standardized wide/narrow ratio under MIL-STD; compatibility with field-deployable wand scanners; simple decoding for low-power portable devices; permanence of metal stamping and impact marking; optional modulo 43 check digit for improved reliability. | - Real-World Outcome: Mandated adoption across all defense supply chains, creating a vast installed base that persists to this day; used in law enforcement evidence chains and postal automation. |
| 5. Retail and Libraries | - Application: Internal SKU labels, library book identification, gift cards, loyalty cards. | - Key Technical Characteristics: Alphanumeric capacity for meaningful stock codes; scratch resistance and durability on plastic; human-readable digits for staff inventory checks; easy printing on thermal and dot matrix printers. | - Real-World Outcome: Legacy systems in department stores and public libraries still operate with Code 39, offering a low-cost and user-friendly inventory management solution. |
| 6. Transportation and Airlines | - Application: Baggage tags, boarding passes, air waybills, cargo tracking. | - Key Technical Characteristics: Long reading distance for conveyor sortation; tolerance to folded, creased, or partially obscured labels; readability under fluorescent and outdoor lighting; fast decoding for high throughput; compatibility with hand-held and fixed-mounted laser scanners. | - Real-World Outcome: Reliable baggage tracking and boarding validation, with many airline ground handling systems still relying on Code 39 for legacy tags. |
| 7. Utilities and Energy | - Application: Meter reading, pipeline tagging, cable labeling, oilfield equipment identification. | - Key Technical Characteristics: UV-resistant printing; resistance to extreme temperatures and corrosive chemicals; readability on metal and plastic tags with low reflectance; permanent marking by laser etching or metal stamping. | - Real-World Outcome: Long-term asset tracking in harsh outdoor and industrial environments, with tags remaining readable for decades. |
| 8. Automotive Aftermarket | - Application: Replacement part labels, direct part marking on components. | - Key Technical Characteristics: Compatibility with dot peen and engraving; clear human-readable part numbers; tolerance to grease and abrasion; use of existing legacy readers and databases. | - Real-World Outcome: Continued use despite newer symbologies, due to cost of migration and proven reliability. |
| 9. Pharmaceutical and Medical Device | - Application: Vial labels, blister packs, instrument sterilization tracking. | - Key Technical Characteristics: Small label capability with narrow bar widths as low as 0.010 inches; resistance to sterilization cycles; high-contrast printing for verification cameras; simple quality metrics based on wide/narrow ratios. | - Real-World Outcome: Enhanced patient safety through lot and expiration tracking; regulatory compliance in many countries. |
| 10. Agriculture and Food Processing | - Application: Produce crates, meat boxes, traceability from farm to store. | - Key Technical Characteristics: Water-resistant printing; readability in cold storage; tolerance to condensation and frost; large label size for easy scanning in wet environments. | - Real-World Outcome: Rapid recall response and improved supply chain transparency. |
| In each of these domains, the same set of technical characteristics appears repeatedly: tolerance to imperfect printing, resilience to environmental damage, bidirectional readability, human-readable backup, and simple decoding. These are not accidental; they were deliberate design choices made by Allais and Stevens in 1974. They understood that real-world conditions are messy, and they built a symbology that could thrive in that mess. They also understood that a barcode is only useful if it can be printed cheaply and read quickly, which is why they avoided complex encoding tables and error-correction algorithms. Their genius was in subtraction, not addition. |
| As we close this chapter, and indeed this book, we must accept that Code 39 will eventually fade from the front lines of automatic identification. New technologies like RFID, Bluetooth beacons, and advanced 2D codes will take over the highest-volume and highest-value applications. But Code 39 will not vanish. It will remain as a reliable fallback, a familiar friend, and a living history lesson. Every time a young engineer asks why the barcode has asterisks at the ends, we will tell the story of Code 39. Every time a scanner fails to read a dirty label and the operator reads the numbers aloud instead, we will see the wisdom of the human-readable design. Every time a new symbology is invented, we will compare it to Code 39 as the baseline of robustness and simplicity. That is the final verdict: Code 39 is the honorable pioneer, and its place in technological history is secure. It may not be the king of efficiency, but it is the father of practicality, and that is a legacy that no amount of supersedure can diminish. |
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cs@easiersoft.com