This course has already ended.

Luet oppimateriaalin englanninkielistä versiota. Mainitsit kuitenkin taustakyselyssä osaavasi suomea. Siksi suosittelemme, että käytät suomenkielistä versiota, joka on testatumpi ja hieman laajempi ja muutenkin mukava.

Suomenkielinen materiaali kyllä esittelee englanninkielisetkin termit. Myös suomenkielisessä materiaalissa käytetään ohjelmaprojektien koodissa englanninkielisiä nimiä kurssin alkupään johdantoesimerkkejä lukuunottamatta.

Voit vaihtaa kieltä A+:n valikon yläreunassa olevasta painikkeesta. Tai tästä: Vaihda suomeksi.

Chapter 12.2: An Introduction to File I/O

About This Page

Questions Answered: How can I load data from a (text) file into my program? Or save data in a file?

Topics: Reading and writing text files. Some other topics will briefly come up as well, including iterators, try, and finally.

What Will I Do? Read. There’s one small, optional assignment.

Rough Estimate of Workload:? One hour. (This is an entirely optional chapter, so you may just skip it, too.)

Points Available: None.

Related Projects: Files (new).


Notes: One of the examples uses sound via, but that isn’t really important for understanding the chapter.


Chapter unavailable in English at the moment   :-(

Due to time pressures, this chapter has not been translated yet for the first English-language offering of O1 in Fall 2018.

We are sorry.

Fortunately, the chapter is entirely optional and there are other resources available in English that cover this material.

We recommend this tutorial by Alvin Alexander, which should convey the gist of what’s going to be here. The Scala methods that are relevant to this chapter largely come from (see the package docs), in particular (see the docs).

You can also take a look at the Files project, which contains the example code for the chapter.

Summary of Key Points

  • Tools for reading and writing input — I/O — are available in the standard libraries that come with programming languages. These tools help the programmer work with files, among other things.
  • You can use the methods in to read and write text files (and other files).
  • Whenever you do file I/O, you need to be alert to the possibility of failures (exceptions) that may occur at runtime.
  • You can learn more about I/O, files, and exception handling in later courses and online.
  • Links to the glossary: I/O; file, text file; runtime error, exception handling.


Please note that this section must be completed individually. Even if you worked on this chapter with a pair, each of you should submit the form separately.


Thousands of students have given feedback that has contributed to this ebook’s design. Thank you!

Weeks 1 to 13 of the ebook, including the assignments and weekly bulletins, have been written in Finnish and translated into English by Juha Sorva.

Weeks 14 to 20 are by Otto Seppälä. That part of the ebook isn’t available during the fall term, but we’ll publish it when it’s time.

The appendices (glossary, Scala reference, FAQ, etc.) are by Juha Sorva unless otherwise specified on the page.

The automatic assessment of the assignments has been programmed by Riku Autio, Jaakko Kantojärvi, Teemu Lehtinen, Timi Seppälä, Teemu Sirkiä, and Aleksi Vartiainen.

The illustrations at the top of each chapter, and the similar drawings elsewhere in the ebook, are the work of Christina Lassheikki.

The animations that detail the execution Scala programs have been designed by Juha Sorva and Teemu Sirkiä. Teemu Sirkiä and Riku Autio have done the technical implementation, relying on Teemu’s Jsvee and Kelmu toolkits.

The other diagrams and interactive presentations in the ebook are by Juha Sorva.

The O1Library software has been developed by Aleksi Lukkarinen and Juha Sorva. Several of its key components are built upon Aleksi’s SMCL library.

The pedagogy of using tools from O1Library (such as Pic) for simple graphical programming is inspired by the textbooks How to Design Programs by Flatt, Felleisen, Findler, and Krishnamurthi and Picturing Programs by Stephen Bloch.

The course platform A+ has been created by Aalto’s LeTech research group and is largely developed by students. The current lead developer is Jaakko Kantojärvi; many other students of computer science and information networks are also active on the project.

For O1’s current teaching staff, please see Chapter 1.1.

Additional credits for this page

This chapter does injustice to music by Kate Bush. Thank you and sorry.

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