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School professors often use various types of challenges or competitions to try to encourage students to do their best.
What would you do if you were taking a developer class, and your professor challenged the class to complete an assignment in the fewest number of lines of code possible?
That is what the student in this story experienced, so when he figured out a loophole in the assignment, he took full advantage and finished the program in zero lines of code.
He really was clever in how he did it. Read through the full story below and see what you think.
Least lines of code contest? okay!
I was taking a computer science class on computer hardware organization, taught by a professor who used to work on the AMD chip architecture.
What kind of person with a history in IT is like this? You would think he should know that technology progresses fast.
He was a tenured professor, set in his old ways, and felt a bit entitled because of his past career prestige. Even in 2009, he demanded that *all* coding assignments are turned in on 3.5 inch floppy drives.
You really had to scrounge to find an old working floppy drive, even in 2009. He was very strict and by the book on his policies.
This sounds like a fun assignment.
Our professor had been teasing us with an upcoming assignment, saying that there had been a multi-year contest to see who could write the assignment program in the least lines of code possible.
Historically, the brightest and smartest student he ever taught accomplished the assignment in 13 lines of code. Typically, students needed about 100 lines of assembly code, and the best can usually do it in about 30 lines of code. I *had* to win, for bragging rights and all.
Assembly code is old and difficult.
We got to writing programs in 6800 assembly code. I had already turned in a few assignments and gotten the hang of assembly, and spent a bit of extra time really getting to understand how programs really work under the hood.
So, every program has “registers” which are working blocks of very small memory on the processor, usually storing a single value. There’s also a “program counter”, which is responsible for executing the next instruction in memory.
Everything boils down to binary code.
A program counter doesn’t always read instructions in sequential order, it might bounce around in memory as you call different functions. I discovered that when we wrote our programs in assembly, they get converted into binary code, and then the binary code is what gets executed by the program counter.
The program counter was a special register which could be manipulated to point at a different block of memory to execute next. Interesting.
When you get down to these ‘low’ levels of programming, things get interesting.
What was even more interesting is that the computer didn’t care where the byte data was stored. It just blindly ran whatever byte data you gave it, without checking whether it was valid memory space for executable instructions or even if it was a valid instruction.
On normal operating systems, memory gets divided into several regions: stack memory, heap memory, and instruction space. If you try to run instruction code in heap or stack memory, usually your operating system pukes and rejects it. But… not in 6800 assembly. This was a very interesting finding for me.
The assignment is simple; the execution is the challenge.
Finally, the day of the infamous assignment arrives. We are supposed to write a memory tester. Basically, you have a big block of memory filled with garbage, you write all zeros to the memory in one pass, verify the memory values are all zero, then write all ones, verify they’re all ones, and if all memory values are verified, the memory is considered “good” and the assignment is complete.
The professor specifically said, “There is no cheating here, get creative, use whatever trick in the book you can imagine.” Okay, challenge accepted! I pride myself on thinking far more creatively than my peers, I have a hacker mindset. No rules? Perfect. He’s going to regret that.
He has his plan of action.
Even more interesting were the few rules the professor gave: Precisely what did not count as a line of code. Three lines did not count: “Start, End, and DCB.” DCB stands for “Declare Constant Block”, which just means you can store some constant values in memory, such as the digits of PI, a few words, or whatever data you wanted.
I immediately saw how I could hack his assignment.
“Does anyone have any questions?” he asked the class. I had a question, but if I asked it, I would give away the hack and the professor would revise the rules. So, I kept my mouth shut.
Even like this, he would be one of the top students.
“Good. In all the classes I have taught, the record has been 13 lines of code. I expect the best of you to get this in about 30 lines of code.” He had been telling this same story for years, to all the classes he taught. Now, it’s time for me to update his story.
So, I wrote my application in about 20-25 lines of assembly code. I spent many hours shaving off instructions, trying to be as clever as I could. It was already pretty impressive. But now it was time to “hack” his assignment.
Success.
When you write assembly code, it gets converted into constant byte data. Remember the ‘declare constant block’ which doesn’t count?
What if I just… copy/paste my compiled byte code and put it into the DCB? And then I put the DCB as the first instruction that gets run? So, I did. And it worked!
This is very impressive.
The program counter started at the first byte in memory, didn’t care that instruction code was in stack memory, and it just executed it. My whole assignment was just an unreadable block of byte code pasted into a DCB and it worked perfectly. Zero lines of code.
I announced on our student message board that I had broken the record for least lines of code. I had accomplished the impossible, by completing the assignment in zero lines of code.
Even the professor doesn’t grasp it at first.
Other students were astounded and in disbelief, guessing at how I could have done this. I told them that once the assignment due date had passed, I would reveal my secret.
We turned in our assignments. No late turn ins, as per professors policy. All floppy disks had been placed. Finally, the professor asked me to explain how I had done it. I was a bit sleep deprived (having been awake until 5am), so I wasn’t super coherent.
There is no such thing as cheating in this assignment.
“I took my program and wrote it as small as I could, then I took the resulting binary and converted it into a DCB, set that as the first block of data, and the program ran flawlessly.” (to paraphrase)
“Wait, you can’t do that! That’s cheating!” the professor replied in shock. I was ready for this reaction.
I bet this was a lot of fun.
“Nope, you specifically said that there were no rules and that DCB did not count as a line of code. So, I hacked your assignment on a technicality and accomplished it in zero lines of code!” I said triumphantly.
I got ’em. The professor couldn’t refute me and had to admit that what I did was clever and he’d have to think about it, and acknowledged I had won his contest.
The professor is a sore loser.
A week later, he announces to the class that he was riding his bike home from work, thinking about what I did and he was revoking my ‘victory’ by changing the rules of the assignment.
Therefore, my entry was ‘invalid’. I was too sleep deprived and unprepared to argue, I didn’t care anymore, I won his silly little game and he’s just a sore loser for changing the rules post-hoc after the game is over.
He can’t take that away from me. Even if I counted my actual lines of code, I still outperformed all of my peers.
Honestly, he found a very clever way to beat the challenge. The professor should be proud, even if he updates the rules for next year.
Check out what the people in the comments have to say about this fun story.
This person is surprised nobody else figured this out.
Here is someone who thinks the professor was wrong.
This commenter says it isn’t fair to make rule changes retroactive.
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The professor was out of line.
Hopefully his grade didn’t suffer.
He said there was no such thing as cheating for this assignment. Why would he change those rules after the fact?
I can see him adjusting the rules for next year, but for this student, he should have been more supportive.