How do programmers work together on a project?

I've always programmed alone, I'm still a student so I never programmed with anyone else, I haven't even used a version control system before.

I'm working on a project now that requires knowledge of how programmers work together on a piece of software in a company.

How is the software compiled? Is it from the version control system? Is it by individual programmers? Is it periodic? Is it when someone decides to build or something? Are there any tests that are done to make sure it "works"?

Anything will do.

Actually, there are as many variations on these processes as many companies there are. Meaning: every company has a little bit different conventions than others, but there are some common best practices that are generally used in most places.

Best practices that are always useful

• All the source code of the project and anything that is required to build it is under version control (also called source control). Anyone should be able to build the entire project with one click.
  Furthermore, unnecessary files (object files or compiled binaries) should not be added to the repository, as they can be regenerated quite easily and would just waste space in the repo.
• Every developer should update and commit to the version control a few times per day. Mostly when they have finished the task they are working on and tested it enough so they know that it doesn't contain trivial bugs.
• Again: anyone should be able to build the project with a single click. This is important and makes it easy to test for everyone. Big advantage if non-programmers (eg. the boss) are able to do so, too. (It makes them feel to be able to see what the team is working on exactly.)
• Every developer should test the new feature or bug fix they are adding before they commit those to the repository.
• Set up a server that regulary (in predetermined intervals) updates itself from the repository and tries to build everything in the entire project. If it fails, it sends e-mails to the team along with the latest commits to the version control (since which commit did it fail to build) to help debug the issue.
  This practice is called continuous integration and the builds are also called nightly builds.
  (This doesn't imply that developers should not build and test the code on their own machines. As mentioned above, they should do that.)
• Obviously, everyone should be familiar with the basic design/architecture of the project, so if something is needed, different members of the team doesn't have to reinvent the wheel. Writing reusable code is a good thing.
• Some sort of communication is needed between the team members. Everyone should be aware of what the others are doing, at least a little. The more, the better. This is why the daily standup is useful in SCRUM teams.
• Unit testing is a very good practice that makes testing the basic functionality of your code automatically.
• A bug tracking software (sometimes called time tracking software) is a very good means of keeping track what bugs are there and what tasks the different team members have. It is also good for testing: the alpha/beta testers of your project could communicate with the development team this way.

These simple things ensure that the project doesn't go out of control and everyone works on the same version of the code. The continuos integration process helps when something goes terribly bad.

It also prevents people from committing stuff that don't build to the main repository.
If you want to include a new feature that would take days to implement and it would block other people from building (and testing) the project, use the branches feature of your version control.

If that is not enough, you can set it up to do automated testing, too, if that is possible with the project in question.

Some more thoughts

The above list can be very heavyweight at first glance. I recommend that you follow it on an as-needed basis: start with a version control and a bug tracker, then later on set up the continuous integration server, if you need it. (If it's a large project, you're gonna need it very soon.) Start writing unit tests for the most important parts. If it's not enough, then write more of them.

Some useful links:
Continuous integration, Daily builds are your friends, Version control, Unit testing

Examples:

For version control, I tend to use Git for my personal projects nowadays. Subversion is also popular, and for example, VisualSVN is quite easy to set up if you use a Windows server. For client, TortoiseSVN works best for many people. Here is a comparison between Git and SVN.

For bug tracking software, Jira and Bugzilla are very popular. We also used Mantis at a previous workplace.

For continuous integration software, there is Teamcity for one (also, CruiseControl and its .NET counterpart are notable).

Answer to your question "who decides the main design of the project?"

Of course, that would be the lead developer.
In companies, the lead developer is the person who talks to the financial / marketing people of the project, and decides the arcithecture according to the financial capability of the company, the planned features the requirements from users, and the time that is available.

It is a complex task, and usually more than one people are involved. Sometimes members of the team are also asked to participate or brainstorm about the design of the entire project or specific parts.

I'm a student as well, who completed a software engineering course recently where the entire semester consisted of a giant group project. Let me just start by saying we could have done with 3 people what it took 12 of us the whole semester to do. Working with people is a tough thing. Communication is key.

Definitely utilize a repository. Each person can remotely access all the code, and add/delete/change anything. But the best part about subversion is that if someone breaks the code, your can revert to an earlier version and assess what went wrong from there. Communication is still key though, know what your teammates are doing so that there are no conflicts. Don't sit on your code either, make quick, meaningful commits to the repository to be the most effective.

**I'd also recommend a bug tracker, such as Redmine. You can set up accounts for everyone, and assign people tasks with different priorities, and also track and see if people have taken care of certain problems, or if more have come up.

And, as has been said before, unit testing will help greatly. Best of luck! Hope this helped :-)