Some of the Worst Programming Mistakes in History that made people sad

Worst Programming Mistakes

With the advancement of technology, we can clearly see that from healthcare to telecommunication and space travel everything is dependent on computers. Although the modern computer arrived in the 1940s it has covered almost everything in our daily life. The rich history of computers couldn’t be impeccable as some worst programming mistakes, halted the usual life and caused monetary loss as well as people’s life. If you are in IT you know why most Software Engineers are frustrated in their life. But, the minor mistakes done by developers in the code caused disaster on a major level and cost people their lives as well.

Here are the 5 worst programming mistakes in history.

1. Y2K Bug

The Y2K Bug (The year 2000 bug), which every 90s kid might have heard was the talk of the town for every IT person or common person. If not resolved on time it could have caused a major setback to the computer system across the world. As, in the 90s, most computer programs had shortened the four-digit year abbreviation to two digits actually to save valuable memory. For example, the year to read 1990 is 90 and 1991 is 91, and so on. But, when the year 2000 was about to come programmers realized that the computer is unable to recognize it as it will be read as 00. Adding to the problem this was also a leap and certain software didn’t have the proper coding to account for the extra one day.

I remember when I was in high school and we already had our hands on the computer this was the topic shared by our computer teacher. At, that time many feared that Y2K could bring down the complete computer system across the world. But, luckily all the computer programmers worked hard to update the computer apps. It cost roughly $300 throughout every industry for the fix. So, actually, nothing happened and life proceeded as normal but with a huge monetary cost.

The reason I have put it on top is that although it did not impact the computer system panic was extremely high not within the IT industry but for every person whether related to the industry or not.

Also Read: Programming languages used in Google, Facebook, Microsoft, etc

2. Therac-25

The Therac-25 radiation therapy machine caused radiation overdose and resulted in the killing of at least six patients. Upon investigation, the finding discovered that the overdose was caused by a software glitch. The insufficient system development and poor software was a result of a programming mistake that costs people’s life.

Since this was a result of human error while coding it is a reminder that code should be written in such a way that it can be easily tested as the machine issue’s real cause was difficulty in performing automated software tests.

I considered it one of the worst programming mistakes because it not only resulted in the programming error or system down but caused the loss of human life.

3. Day of the Living Dead

In 2003 St. Mary’s Mercy Medical Center in Grand Rapids, Michigan, Patients Management System reported that 8,500 patients are dead. It was later discovered that the software glitch in the system incorrectly generated that report but at the time it caused super mayhem. As getting the news of the death of your family/friends is the saddest news that one can hear. Most of the Patients in fact got the report of their own demise which was really discomforting when you are particularly alive. This disaster was harmless unlike Therac-25 because it did not actually kill any patient but generated the wrong report. This software mistake is huge because the news was not only limited to patients and their families but the correspondence went out to insurance companies and Social Security offices.

Since Insurance providers and Social Security ensure eligible patients have Medicare the news caused a big problem.  Later, St. Mary’s Mercy informed patients, insurance providers, and government agencies about the software glitch. Although, the patients actually did not die the news created a lot of trouble for the patients and their families, and the damage control of ensuring continued healthcare coverage was a mess.

4. Prisoner Pre-Alpha: Early Release

Between 2003 and 2005, Michigan state prisoners benefited from the computer programming flaw. Around 23 prisoners got an early release due to a software glitch that reduced the sentence from 39 to 161 days. This is a serious programming mistake as it was an early release of prisoners who are serving in charges of drug and embezzlement charges. This could be more fatal if the bug could have been the cause of the early release of prisoners dabbling in more serious crimes.

These programming mistakes give us the lesson of being more cautious while developing any software. Because, although this software aims to automate the process and makes like simple the result should not be something that brings trouble in the place of peace.

5. World of Warcraft Virus

Every online game player knows what is World of Warcraft. This game once suffered a different kind of computer virus in 2005. A virus called Blood virus emerged as a digital plague that infiltrated a few game servers and killed thousands of characters. Hakkar, the god of Blood which was intended to afflict players within proximity to Hakkar’s body actually infected characters with corrupted blood. The player-to-player transfer of this blood virus occurred outside the realm moreover, non-player characters (NPCs) became carriers.

The first infected server was Archimonde which caused the death of Low-level characters instantly. The powerful characters also didn’t last much longer. Although the virus wasn’t planned to be released outside of Hakkar’s kingdom, the programming mistakes which caused a coding glitch perpetuated the virus via NPCs and pets. Blizzard rolled the server restarts and somehow fixed the blood virus, but thousands of player character corpses littered the World of Warcraft landscape. Although this coding glitch did not actually kill anyone in real or caused financial loss, it affected online games as they take their entertainment very seriously. And, also showed us what might happen if some glitch happen in the real world how the outbreak and panic caused the collapse of complete civilization.


In this article, I have only mentioned the worst programming mistakes which are more related to people’s life where either they lost someone or heard false news about their death. As, well as the biggest outburst of computer programming mistakes for 90’s kids.

So, Developers should put more focus while developing any application or while writing programming and should follow the basic Programming Principles to become good Programmers. Moreover, thorough testing is required before the release of any such software.

We are not expecting the disappearance of Programming mistakes anytime soon, as it is there since the inception of coding. But, there are several programming mistakes in history from which we can learn and stop repeating these mistakes.

You should not just only focus on understanding the easy programming languages for beginners, but also focus on the programming languages that are in demand in IT companies right now.

We would love to know about any other historical examples of bad code that you remember and want to share with us. Also, leave comments about the programming blunders that you have done in your career.

You may also like our Programming section, to know more about IT engineers, but this section covers real work.

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About the Author: Ranjit Ranjan

More than 15 years of experience in web development projects in countries such as US, UK and India. Blogger by passion and SEO expert by profession.

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