DOS Civilization 1 (1991) Bug(s) discussion - What should be fixed in OpenCiv1?

rahorvat · Mar 25, 2024

This thread is intended as a guide and a list of a known bugs

in original DOS Civilization 1 (from year 1991) (that have not been fixed by a latest game version 475.05) and that should/can be fixed in OpenCiv1.

Don't let this thread mislead you regarding the playability of the game. Most of these bugs, or annoyances, are minor, and most of the time game functions normally. Like @Lord_Hill said: "It's funny rereading this thread. You'd think the game barely starts and is almost unplayable, when in fact most of this stuff isn't particularly bothersome at all!"

Majority of the serious bugs are due to stack and/or memory corruption because of an unchecked Array indexes and pointers (The original C compiler is so old that it didn't have any Array index checks). The OpenCiv1 project aims to correct these as well simply because most of the stuff is built into C# language by default.

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 improvement	Settler (when reactivated) can finish improvement that requires multiple turns in one turn	Settler should require multiple turns to finish the multiple turn improvement	If settler is not reactivated it takes exact number of turns to complete improvement	Yes (This clearly should be a cheat and not a default behavior)
Settler building improvement	Settler 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 Wonder	The effect of Copernicus observatory Wonder never stops	The effect of Copernicus observatory Wonder stops after the discovery of Automobile	The DOS Civilization manual on page 84 clearly states that the effect of Copernicus Observatory Wonder should stop after the discovery of automobile	Yes (Official manual clearly documents the correct behavior)
SETI Program Wonder	After completion of SETI Program Wonder the knowledge generated by the cities does not reflect the 50% increase	SETI 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 cities	Yes (Official manual clearly documents the correct behavior)
Sentried unit regains turns	If 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 Manual	Yes (According to official manual)
Settler can build Roads/Railroads on ocean	If 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 ocean	Official Manual	Yes
Score screen / Arctic anomaly	When 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	Arctic Anomaly This is when you get this kind of stuff: EDIT: This is how the anomaly appears on the "see again your game" screen (I customized the civs colors) :) Already partly discussed here, its origin seems quite mysterious, although it may be elucidated now. For a while I thought it was... forums.civfanatics.com Arctic Anomaly This is when you get this kind of stuff: EDIT: This is how the anomaly appears on the "see again your game" screen (I customized the civs colors) :) Already partly discussed here, its origin seems quite mysterious, although it may be elucidated now. For a while I thought it was... forums.civfanatics.com	Yes
Arctic anomaly	If 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 columns	Founding your city on any legal tile has no impact on the game	Interesting bug allows super sized cities Hello everyone! I always wondered if and how you can get a city larger than the known limit of 63. Well, when generating the map I got a - at least for me - special situation. At the top of the map, several fields were generated at the "end of the world". Some of them seem special. When I... forums.civfanatics.com	Yes
Pollution bug	At 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	Pollution is generated based on the standard ruleset regardless of the in game date	Pollution bug <- NAILED Although I never put it at the center of my focus, stories about the "pollution bug" have been kept roaming at the back of my mind ever since I became active on those forums, and read people mentioning it here and there. Being more or less done with the City Process routine (I'm not done yet... forums.civfanatics.com	Yes
Advisor bug	If you have advisors enabled and the domestic and military advisors run out of suggestions (because you've built everything) the game will crash	The game should continue after the advisors have no more advice	Section A: General Information - CivFanatics Civ1 FAQ: General Information How can I tell which version of Civ I have? Which is the best version of Civ? What is the Advisory Bug? What is the Undefended City Bug? What is the Civ score Bug? What is the Bomber Bug? What is the Date Line Bug? What is the Ghost Civilization Bug? www.civfanatics.com	Yes
City improvement bug	If 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	Hi tech city Improvement glitch Hi everyone. I haven't been here in awhile, since its been at least 3 years since I've had a pc. Now that I do, I got back into Civ 1 (for DOS) a little. What's annoying me is when I reach a high technology level, I can't build city upgrades in cities without a lot of pre-existing upgrades. The... forums.civfanatics.com	Yes
Great library destruction	If 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 crashes	The game should allow a city with a great library to be destroyed	Great Library destruction Have any of you destroyed the Great Library before it expires? I did just that the other day, and then something strange happened. First I got this message. Apparently the barbarians get the destroyed wonders. After getting the great library the barbarians established their own... forums.civfanatics.com Barbarian Great Library bug: investigation Probably many of you know that when the Great Library is destroyed (or captured by Barbarians) game goes crazy in various ways. It can crash randomly, it writes some (it seems) random data at (it seems) some random places. Why? At the first glance, we can see that game checks only that city of... forums.civfanatics.com	Yes
Map wrap movement (go to) bug	The 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 wraps	The game should take into account horizontal wrapping when calculating go to routes	Fortification and sentry bug concerning AI in civ 1 ? There might be some kind of fortification bug in civilization 1, where the AI cannot attack fortified units. I noticed such a case with a musketeer on a mountain. Only after unfortifieing and refortifieing could the AI attack it. If true then this could explain why the AI sends and stacks so... forums.civfanatics.com	Yes
Diplomacy, paying for a War	If 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, Pay for declaration of war I take advantage of the fact that this forum has many experts in this game to ask about the subject matter of the title of this post. The fact is that no matter how many times you pay a civilization and in the text of the conversation it says that they have declared war on another civilization... forums.civfanatics.com	Yes
Graphic crash when trading for invention	If 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.	An interesting bug. Playing a game of Civ fooling around, it occurred to me to give technology to the Egyptians so that they could defend themselves from other civilizations. When I exchange 4 or 5 technologies the diplomacy screen changes and the following appears: I was totally unaware of this bug, and in... forums.civfanatics.com	Yes
Bomber runs out of fuel after one turn if clicked	If 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 destroyed	Clicking on a bomber should not destroy it	Section A: General Information - CivFanatics Civ1 FAQ: General Information How can I tell which version of Civ I have? Which is the best version of Civ? What is the Advisory Bug? What is the Undefended City Bug? What is the Civ score Bug? What is the Bomber Bug? What is the Date Line Bug? What is the Ghost Civilization Bug? www.civfanatics.com	Yes
Go To function	The Go To function is poorly implemented with numerous bugs not honoring the movement rate properly.	Go To should choose the fastest route considering the terrain, roads and railroads in the movement of the unit.	Numerous sources	Yes
Settlers	The work of the multiple settlers with same task on a single square is not cumulative.	The multiple settlers working on a same task should finish the work more faster.	Numerous sources	Yes
City neighborhood	The neighborhood screen doesn't properly update/show squares with invisible enemy units.	The occupied squares, even ones with invisible enemy unit should be clearly marked with a red rectangle.	Numerous sources	Yes
Switching production from cheap one to a more costly one without any penalty	There are numerous ways to exploit this. Wonders, buildings and units have different shield cost and that is easily exploitable.	There should be some penalty for changing the production queue. It also makes sense if you refit your production queue from, for example, Settler to Cathedral there should be some penalty for changing the production queue.	Numerous sources	Yes
Unit sentry bug	When some units are in sentry mode, there are multiple exploits to get additional or unlimited moves.	Two passenger-carrying ships can travel the world (triremes still have to be careful). One ship moves until it has one movement point, then sentries. It's partner then moves into the same square and wakes it up with an Unload command. The ships then swap roles. The second ship moves on and sentries, the first ship wakes it up. Repeat. The same ships can similarly escort a battleship anywhere it may be needed.	Numerous sources	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.

Lord_Hill · Mar 25, 2024

Description	Wrong behavior	Correct behavior	Reference(s), Link(s) or explanation	Fix?
Sentried unit regains turns	If 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 railroads	If 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 railroaded		Yes (it seems unlikely that this was intentional, it makes no sense that settlers would have this ability)
Arctic anomaly 1	When 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	Arctic Anomaly This is when you get this kind of stuff: EDIT: This is how the anomaly appears on the "see again your game" screen (I customized the civs colors) :) Already partly discussed here, its origin seems quite mysterious, although it may be elucidated now. For a while I thought it was... forums.civfanatics.com Arctic Anomaly This is when you get this kind of stuff: EDIT: This is how the anomaly appears on the "see again your game" screen (I customized the civs colors) :) Already partly discussed here, its origin seems quite mysterious, although it may be elucidated now. For a while I thought it was... forums.civfanatics.com	Yes (a clear bug)
Arctic anomaly 2	If 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.	Interesting bug allows super sized cities Hello everyone! I always wondered if and how you can get a city larger than the known limit of 63. Well, when generating the map I got a - at least for me - special situation. At the top of the map, several fields were generated at the "end of the world". Some of them seem special. When I... forums.civfanatics.com	Yes (a clear bug)
Pollution bug	At 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.	Pollution bug <- NAILED Although I never put it at the center of my focus, stories about the "pollution bug" have been kept roaming at the back of my mind ever since I became active on those forums, and read people mentioning it here and there. Being more or less done with the City Process routine (I'm not done yet... forums.civfanatics.com	Yes (a clear bug)
Advisor bug	If you have advisors enabled and the domestic and military advisors run out of suggestions (because you've built everything) the game will crash	The game should continue after the advisors have no more advice	Section A: General Information - CivFanatics Civ1 FAQ: General Information How can I tell which version of Civ I have? Which is the best version of Civ? What is the Advisory Bug? What is the Undefended City Bug? What is the Civ score Bug? What is the Bomber Bug? What is the Date Line Bug? What is the Ghost Civilization Bug? www.civfanatics.com	Yes (a clear bug)
City improvement bug	If 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.	Hi tech city Improvement glitch Hi everyone. I haven't been here in awhile, since its been at least 3 years since I've had a pc. Now that I do, I got back into Civ 1 (for DOS) a little. What's annoying me is when I reach a high technology level, I can't build city upgrades in cities without a lot of pre-existing upgrades. The... forums.civfanatics.com	Yes (a clear bug)
Great library destruction	If 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 crashes	The game should allow a city with a great library to be destroyed.	Great Library destruction Have any of you destroyed the Great Library before it expires? I did just that the other day, and then something strange happened. First I got this message. Apparently the barbarians get the destroyed wonders. After getting the great library the barbarians established their own... forums.civfanatics.com Barbarian Great Library bug: investigation Probably many of you know that when the Great Library is destroyed (or captured by Barbarians) game goes crazy in various ways. It can crash randomly, it writes some (it seems) random data at (it seems) some random places. Why? At the first glance, we can see that game checks only that city of... forums.civfanatics.com	Yes (a clear bug)
Map wrap movement bug	The 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.	Fortification and sentry bug concerning AI in civ 1 ? There might be some kind of fortification bug in civilization 1, where the AI cannot attack fortified units. I noticed such a case with a musketeer on a mountain. Only after unfortifieing and refortifieing could the AI attack it. If true then this could explain why the AI sends and stacks so... forums.civfanatics.com	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.

rahorvat · Mar 25, 2024

Lord_Hill said:
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.

Thanks, will add them to a main list

Humungus · Mar 25, 2024

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

rahorvat · Mar 26, 2024

Humungus said:
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.

Lord_Hill · Mar 26, 2024

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)

Section A: General Information - CivFanatics

Civ1 FAQ: General Information How can I tell which version of Civ I have? Which is the best version of Civ? What is the Advisory Bug? What is the Undefended City Bug? What is the Civ score Bug? What is the Bomber Bug? What is the Date Line Bug? What is the Ghost Civilization Bug?

www.civfanatics.com

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.

Civil War in Civ1

How civil war event works in CivDos... 1)Civil war event is called if AI civ has more than 4 cities and somebody captured their capital and human player's place is lower than place of this AI civ. Problem: city counter and civ place are updated only at the beginning of new turn, so as long as...

forums.civfanatics.com

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.

rahorvat · Mar 27, 2024

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.

Mize · Mar 28, 2024

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).

rahorvat · Mar 28, 2024

Mize said:
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.

Lord_Hill · Mar 28, 2024

@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.

Theov · Mar 29, 2024

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.

Mize · Mar 29, 2024

rahorvat said:
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.

Lord_Hill said:
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.

rahorvat · Mar 29, 2024

Mize said:
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)

rahorvat · Mar 29, 2024

Theov said:
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)

rahorvat · Mar 29, 2024

rahorvat said:
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?

rahorvat · Mar 29, 2024

Lord_Hill said:
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++

Lord_Hill · Mar 29, 2024

Diplomacy as a whole is very flaky. Paying to force a war for example just doesn't work.

rahorvat · Mar 29, 2024

Lord_Hill said:
Diplomacy as a whole is very flaky. Paying to force a war for example just doesn't work.

OK, then another to do entry

Lord_Hill · Apr 2, 2024

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!

Description	Wrong behaviour	Correct Behaviour	References/explanation	Fix
Bomber runs out of fuel after one turn if clicked	If 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 destroyed	Clicking on a bomber should not destroy it	Section A: General Information - CivFanatics Civ1 FAQ: General Information How can I tell which version of Civ I have? Which is the best version of Civ? What is the Advisory Bug? What is the Undefended City Bug? What is the Civ score Bug? What is the Bomber Bug? What is the Date Line Bug? What is the Ghost Civilization Bug? www.civfanatics.com	Yes
Graphical corruption when trading for invention	If 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.	An interesting bug. Playing a game of Civ fooling around, it occurred to me to give technology to the Egyptians so that they could defend themselves from other civilizations. When I exchange 4 or 5 technologies the diplomacy screen changes and the following appears: I was totally unaware of this bug, and in... forums.civfanatics.com	Yes
Paying for a declaration of war broken	If 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.	Pay for declaration of war I take advantage of the fact that this forum has many experts in this game to ask about the subject matter of the title of this post. The fact is that no matter how many times you pay a civilization and in the text of the conversation it says that they have declared war on another civilization... forums.civfanatics.com	Yes

rahorvat · Apr 4, 2024

Lord_Hill said:
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!

Thank you very much. The last one was already on my list

DOS Civilization 1 (1991) Bug(s) discussion - What should be fixed in OpenCiv1?

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