DOS Civilization 1991 Bug(s) discussion - What should be fixed in OpenCiv1?

rahorvat

Warlord
Joined
Mar 12, 2023
Messages
145
Location
Croatia, EU
This thread is intended as a guide and a list of a known bugs 🐞 in original DOS Civilization 1991 (that have not been fixed by a latest game version 475.05) and that should be fixed in OpenCiv1.

What constitutes a Bug? The bug is a behavior that crashes the game, is not intended or is in a disagreement with the official Manual. From Wikipedia: "A software bug is an error, flaw or fault in the design, development, or operation of computer software that causes it to produce an incorrect or unexpected result, or to behave in unintended ways."

Description
Wrong behavior
Correct behavior
Reference(s), Link(s) or explanation
Fix?
Settler improvementSettler (when reactivated) can finish improvement that requires multiple turns in one turnSettler should require multiple turns to finish the multiple turn improvementIf settler is not reactivated it takes exact number of turns to complete improvementYes (This clearly should be a cheat and not a default behavior)
Settler building improvementSettler build the improvement by themselves (one at a time)Settler built improvements should/could be partially built and or built faster with multiple settlers working on the same task-Maybe (Needed further discussion, if this feature doesn't change the rules of the game that much)
Copernicus observatory WonderThe effect of Copernicus observatory Wonder never stopsThe effect of Copernicus observatory Wonder stops after the discovery of AutomobileThe DOS Civilization manual on page 84 clearly states that the effect of Copernicus Observatory Wonder should stop after the discovery of automobileYes (Official manual clearly documents the correct behavior)
SETI Program WonderAfter completion of SETI Program Wonder the knowledge generated by the cities does not reflect the 50% increaseSETI Program Wonder increases the knowledge generated by your cities by 50%The DOS Civilization manual on page 87 clearly states increase in knowledge generated by the citiesYes (Official manual clearly documents the correct behavior)
Sentried unit regains turnsIf you move a unit into a city and sentry it before all of its moves are used up, un-sentrying the unit will restore all of its moves on the same turn.Sentrying a unit in a city should not change the number of moves a unit has left in a turn.Official ManualYes (According to official manual)
Settler can build Roads/Railroads on oceanIf you use a settler build road/railroad command on an ocean square whilst in a sea transport unit, nearby cities receive the trade bonus as if a land square has road/railroad.Roads or railroads can't be built on oceanOfficial ManualYes
Score screen / Arctic anomalyWhen too many wonder pictures are displayed on the F9 score screen, an overflow occurs causing the top tiles of the map to change and become corrupted. This can lead to tiles with illegal yields or cause the game to crash completely.Viewing the score screen has no impact on game regardless of the number of wonders constructed Yes
Arctic anomalyIf you found a city on any tile in the last two or first two vertical columns on the map, this can also trigger corruption on the top tiles leading to crashes and strange behavior. This can only occur on the Earth map or custom maps which have land tiles in these columnsFounding your city on any legal tile has no impact on the game Yes
Pollution bugAt a certain point late in the game after many future techs have been discovered (the exact point is dependent on difficulty level and other factors), pollution will be generated at a massively increased ratePollution is generated based on the standard ruleset regardless of the in game date Yes
Advisor bugIf you have advisors enabled and the domestic and military advisors run out of suggestions (because you've built everything) the game will crashThe game should continue after the advisors have no more advice Yes
City improvement bugIf you have a large city with many techs discovered but few buildings already constructed, the list of buildings/wonders in the city screen isn't large enough to contain all the options and breaks. If you click 'more' in this state you will get a blank menu and be unable to build anythingThe game should be able to handle a list of all possible build options in the city screen Yes
Great library destructionIf you allow land barbarians to destroy a city containing the great library wonder, this causes strange side effects (including a pollution bug and corrupt tech tree) and eventually crashesThe game should allow a city with a great library to be destroyed Yes
Map wrap movement (go to) bugThe go to routine (both for the player and AI movement) does not properly handle map wrapping. An AI ship can get stranded in an infinite loop trying to cross the vertical line of tiles where the map wrapsThe game should take into account horizontal wrapping when calculating go to routes Yes
Diplomacy, paying for a WarIf you successfully bribe an AI into declaring war on another civ, they will never actually do it.Bribing an AI to declare war should cause them to actually declare war.Official manual, Yes
Graphic crash when trading for inventionIf you receive invention via a trade rather than discovering it yourself, the routine to switch the 'ancient' government picture with the 'modern' one does not run properly and diplomacy graphics is corrupted.Trading for invention should have no impact on diplomacy graphics. Yes
Bomber runs out of fuel after one turn if clickedIf you click on a bomber and attempt to reactivate it after its first turn is over (but before the next turn) it will immediately 'run out of fuel' and be destroyedClicking on a bomber should not destroy it Yes
¸

Bug report Template (please no abbreviation(s) or lengthy explanations, please be as concise and clear as possible):

- Description: (Brief description of the bug)
- Wrong behavior: (What is the unintended behavior that the bug causes?)
- Correct behavior: (What should be the correct behavior?)
- Reference(s), Link(s) or brief explanation: (Reference(s) to an original manual or a Link(s) to a discussion that clearly marks this as a bug)
- Fix: (Yes / No / Maybe, and/or a brief explanation why)

You can attach a screenshot if that will help to explain the bug.
 
Last edited:
DescriptionWrong behaviorCorrect behaviorReference(s), Link(s) or explanationFix?
Sentried unit regains turnsIf you move a unit into a city and sentry it before all of its moves are used up, un-sentrying the unit will restore all of its moves on the same turn.Sentrying a unit in a city should not change the number of moves a unit has left in a turn.Yes (This clearly should be a cheat and not a default behavior)
Ocean railroadsIf you use a settler's railroad command on an ocean square whilst in a sea transport unit, nearby cities receive the trade bonus as if a land square had been railroaded.Ocean squares cannot be railroadedYes (it seems unlikely that this was intentional, it makes no sense that settlers would have this ability)
Arctic anomaly 1When too many wonder pictures are displayed on the F9 score screen, an overflow occurs causing the top tiles of the map to change and become corrupted. This can lead to tiles with illegal yields or cause the game to crash completely.Viewing the score screen has no impact on game regardless of the number of wonders constructed Yes (a clear bug)
Arctic anomaly 2If you found a city on any tile in the last two or first two vertical columns on the map, this can also trigger corruption on the top tiles leading to crashes and strange behaviour. This can only occur on the Earth map or custom maps which have land tiles in these columns.Founding your city on any legal tile has no impact on the game. Yes (a clear bug)
Pollution bugAt a certain point late in the game after many future techs have been discovered (the exact point is dependent on difficulty level and other factors), pollution will be generated at a massively increased rate, completely ignoring the documented game rules that are supposed to govern it.Pollution is generated based on the standard ruleset regardless of the in game date. Yes (a clear bug)
Advisor bugIf you have advisors enabled and the domestic and military advisors run out of suggestions (because you've built everything) the game will crashThe game should continue after the advisors have no more advice Yes (a clear bug)
City improvement bugIf you have a large city with many techs discovered but few buildings already constructed, the list of buildings/wonders in the city screen isn't large enough to contain all the options and breaks. If you click 'more' in this state you will get a blank menu and be unable to build anything.The game should be able to handle a list of all possible build options in the city screen. Yes (a clear bug)
Great library destructionIf you allow land barbarians to destroy a city containing the great library wonder, this causes strange side effects (including a pollution bug and corrupt tech tree) and eventually crashesThe game should allow a city with a great library to be destroyed. Yes (a clear bug)
Map wrap movement bugThe goto routine (both for the player and AI movement) does not properly handle map wrapping. An AI ship can get stranded in an infinite loop trying to cross the vertical line of tiles where the map wraps.The game should take into account horizontal wrapping when calculating goto routes. Yes (a clear bug)

I have started with these 10 bugs. I've tried to stay way from 'the AI could do better' stuff which aren't really bugs but limitations and focus on crashes, exploits and incorrect behaviour.
 
For the fun, 2 graphic bugs
- a structural element of the space ship isn't necessary to launch it
- there is a green pixel on the Cesar toga on diplomacy screen
 
For the fun, 2 graphic bugs
- a structural element of the space ship isn't necessary to launch it
- there is a green pixel on the Cesar toga on diplomacy screen
I have heard that people run in a funny situations with their space ships, but I think they (Microprose) just didn't care about little details.
I agree that there is definitely room for improvement as with AI, but this doesn't constitute a real bug.
 
There are a few other so called bugs mentioned in the faq and 'cheats' page here that I just want to confirm are NOT bugs in my opinion (as far as OpenCiv1 is concerned)

The 'ghost civilization bug' was a v1 bug that was fixed in later versions. If you destroy a settler of a new Civ before they found a city, the credit will go to the barbarians but the game won't crash. Looks a bit off that you don't get credit but the important thing is that it doesn't crash anymore.

The 'tale of one city' I don't believe is valid either as @tupi 's research shows that a civ needs at least 4 cities to be vulnerable to a schism / civil war event in v5. It can't happen if they only have one city.
There's another bug in that thread mentioned by @Mize. The game gets very confused if you trigger a civil war twice in a single turn! Not easy to engineer that, possibly not worth investigation.

The 'undefended city bug' is definitely real, it's happened to me a few times and there's even code in @darkpanda 's JCivEd to correct saves that have cities like that, but I don't think its fair to add to the list as no one appears to know how cities get into that state in the first place!

Apparently clicking on a bomber again after its first turn is over destroys it, will have to check that one out.
 
Just one factual bug (or error, if you want to call it that):
The other players can contact you without Alphabet and Writing (Diplomats), but you can't, they can even ask you to "sign" peace treaty.
By my logic that should be corrected, either by introducing verbal consent (makes more sense) or removing that option altogether before discovery of Alphabet and Writing.
Another thing is that you (as a player) should be able to contact other players via adjacent units.
 
The settler thing is fundamentally wrong and I'm not sure there's a way to fix it by hacking the original, maybe one of the clones can address the issue. What I mean is that squares--not settlers--should really store the 'work' (settler turns invested in the improvement).
 
The settler thing is fundamentally wrong and I'm not sure there's a way to fix it by hacking the original, maybe one of the clones can address the issue. What I mean is that squares--not settlers--should really store the 'work' (settler turns invested in the improvement).
Welcome,
Well, that just means that another settler could finish the work later.
There are opposing point of views on this:
1) if the settler doesn't finish the work, the work shouldn't be done.
2) the partial work should be stored and the settler can finish the work other settler unit started before (like in StarCraft, for example).

Not sure what side to take on that ;)

The whole point of this discussion is to find common ground about the fixes that we can do in OpenCiv1.
 
@Mize is an excellent Civ 1 player, half the discussions on here around exotic bugs and outlier AI behaviour seem to come from your in depth threads :)

If you ever have the time/motivation I'd suggest giving @rahorvat 's OpenCiv1 a try (it's not a clone as such, it's a disassembly rewritten in C++ so behaviour should be identical to DOS v5 once complete). You've got a higher chance than most of spotting any weirdness regarding the underlying rules not matching DOS.
 
2) the partial work should be stored and the settler can finish the work other settler unit started before (like in StarCraft, for example).

To me this has always made more sense than a settler carrying around a prefabricated fort. When I first started playing civ as a kid, I just naturally thought it should work that way and that if you assign several settlers the same task in the same square it would get done quicker. That's how I found out that it didn't actually work that way and that you could charge up settlers.

If you ever have the time/motivation I'd suggest giving @rahorvat 's OpenCiv1 a try

I'd love to, but time is indeed a factor. Putting it on my long and dusty to-do list.
 
To me this has always made more sense than a settler carrying around a prefabricated fort. When I first started playing civ as a kid, I just naturally thought it should work that way and that if you assign several settlers the same task in the same square it would get done quicker. That's how I found out that it didn't actually work that way and that you could charge up settlers.
Well, when I think about it, its logical and makes sense. Will put on a maybe list. Also, I don't want to alter the original rules too much... as that would make it too different from original (the goal is a rewrite, not a new game) ;)
 
Last edited:
if it helps he ai, then one turn settlers should be a thing - otherwise humans would just abuse it
Or make it a feature, not a bug.
Yes, but it definitely should be a cheat and not a regular thing (default rules are pretty clear on this) :)
 
Last edited:
Just one factual bug (or error, if you want to call it that):
The other players can contact you without Alphabet and Writing (Diplomats), but you can't, they can even ask you to "sign" peace treaty.
By my logic that should be corrected, either by introducing verbal consent (makes more sense) or removing that option altogether before discovery of Alphabet and Writing.
Another thing is that you (as a player) should be able to contact other players via adjacent units.
No thoughts on this one?
 
If you ever have the time/motivation I'd suggest giving @rahorvat 's OpenCiv1 a try (it's not a clone as such, it's a disassembly rewritten in C++ so behaviour should be identical to DOS v5 once complete). You've got a higher chance than most of spotting any weirdness regarding the underlying rules not matching DOS.
Just a quick correction it's rewritten in C# not C++ :)
 
OK, I think I've finally ran out of bugs to document. It was a fun exploration of the forum history, I discovered a whole bunch of ones I didn't know about before! :)

DescriptionWrong behaviourCorrect BehaviourReferences/explanationFix
Bomber runs out of fuel after one turn if clickedIf you click on a bomber and attempt to reactivate it after its first turn is over (but before the next turn) it will immediately 'run out of fuel' and be destroyedClicking on a bomber should not destroy it Yes
Graphical corruption when trading for inventionIf you receive invention via a trade rather than discovering it yourself, the routine to switch the 'ancient' government picture with the 'modern' one does not run properly and diplomacy graphics is corrupted.Trading for invention should have no impact on diplomacy graphics. Yes
Paying for a declaration of war brokenIf you successfully bribe an AI into declaring war on another civ, they will never actually do it.Bribing an AI to declare war should cause them to actually declare war. Yes
 
Top Bottom