SuperMemo files


Program files

These are the files used by a typical SuperMemo installation:

Collection files

KNO file

Most important fields of the KNO file

The size of variables used above in bytes is: integer and longint 4, byte 1, real48 6, and word 2.


Your collection can suddenly appear empty!
Disappearing material
With luck, you can recover from "empty backup"!
Backing up Advanced English
Recovering from file mix-up

Disappearing learning material

From: hojinil
Country: South Korea
Sent: Wednesday, April 11, 2001 4:29 AM


I used Add New and I added lots of stuff but next time when I opened collections I couldn't find any of them. It was gone!


Please make sure the following two conditions are met:

  1. You are not copying or moving files behind the back of SuperMemo (e.g. with Windows Explorer)
  2. You are not using two independent copies of SuperMemo (each may use a different default collection)

With File : Open collection, you go to the exactly same location where you last left your collection. If some files are moved or deleted behind the back of SuperMemo, it will often attempt to recreate missing files and open the collection regardless. Unless you delete your collection or delete its folders, your learning material should remain safe

Collections may look like empty

From: Michael Duggan
Country: Canada
Sent: Nov 2, 1998


I was cleaning up my hard drive and attempted to move SuperMemo from one folder to another folder. In the process I lost the data for a number of collections. Can I retrieve these data files and place them back in my collection? How do I do that?


It is recommended to always move collections with File : Copy collection in SuperMemo. Otherwise, a frequent mistake is to copy the kno file without the folder that contains the actual collection files.

Some customers also fall victim of the following scenario:

  1. move the whole SuperMemo folder to a new location using Windows tools
  2. start SuperMemo from the new location
  3. SuperMemo inspects supermemo.ini for the location of most recently used files and looks for them in the old location
  4. SuperMemo displays Cannot find <collection name> at <old location>. Create new files?
  5. if the users responds with Yes, SuperMemo creates empty files with the old name
  6. it all looks like collections became empty while they are safely stored at the new location

The simplest remedy is to answer No in Step 5 and open collections at the new location with File : Open collection. You can also delete supermemo.ini (or its portion that begins with [SYSTEMS] which keeps the location of collections). This way, SuperMemo will 'forget' about the old location of files

Backup disaster: collection lost!

From: Przemek S.
Country: Poland
Sent: June 8, 2000


I used to regularly back up my Advanced English on a second hard disk. Today I tried to restore my backup and ... it looks as it is empty! Only one element inside! Help!!!


There is a frequent mistake users make. To backup a collection, you need to copy both the kno file and the associated folder (e.g. file ae.kno and the folder [AE]). Some inexperienced users copy only the kno file which is less than 20KB of data (e.g. 950 bytes in SuperMemo 17)! If you try to open an orphaned kno file, SuperMemo will reconstruct an empty folder structure.

To avoid this problem: Always back up collections with File : Copy collection or File : Backup. Do not use external tools unless you understand Windows, files, folders and SuperMemo very well!

To resolve the problem: it is possible the original folder associated with the kno file still exists on the hard disk! You can search for some files characteristic for SuperMemo (e.g. compon.dat or sm8opt.dat). Make an inventory of all kno files (search for *.kno) and all SuperMemo collection folders (search for compon.dat) on your hard disk. Once the inventory is made, try to carefully match up knos and folders and copy kno files to match the folders. Chances are that File : Open collection on one of these files will restore the lost backup. Note that you can easily find empty collections by checking the size of workload.dat (burden.dat in older SuperMemos). This file contains repetitions and is zero-sized on collections with no learning process

Mixed up collection files

From: Richard D
Country: USA
Sent: Feb 15 , 2001


While backing up my collections, I have mixed up some files. As a result, my precious collection on Emergency Medicine became empty. I have lots of backups but I find it difficult to locate the appropriate files. Can you suggest how to resolve it?


To backup a collection, you need to copy both the kno file and the associated folder (e.g. file Emergy Medicine.kno and the folder [EMERGENCY MEDICINE]). Some inexperienced users copy only the kno file! If you try to open the orphaned Emergency Medicine.kno file, SuperMemo will reconstruct an empty folder structure and the collection will be empty. What is worse, if you run File : Repair collection, the kno file will be "corrected" to match data of the empty collection (e.g. Memorized will be set to zero, etc.).

To restore your collection in such cases you need to:

  1. Locate the EMERGENCY MEDICINE folder which contains all the most important data:
    1. Search for the folder EMERGENCY MEDICINE
    2. If you do not find it, search for folders like EMERG*
    3. If you fail, search for files text.rtx on all your hard disks (including backup drives, networks and CDRs)
    4. Sort text.rtx files by size (the more work you put in the collection, the larger the file)
    5. You can view the content of text.rtx and see if it corresponds with the material you put into your collection
    6. If you do not find the folder with the matching text.rtx, you have probably lost your files for good
  2. Locate the Emergency Medicine.kno file:
    1. Search for the file Emergency Medicine.kno
    2. If you do not find it, search for files like Emerg*.kno
    3. If you fail, search for all *.kno files
    4. If you fail, take any kno file as a substitute (File : Repair collection may occasionally be able to completely restore lost information)
  3. Put both the EMERGENCY MEDICINE folder (or the folder found in Step 1) and Emergency Medicine.kno file (or equivalent from Step 2) in the same folder (e.g. c:\recovered). Make sure the name of kno file matches the name of the folder. For example, if the folder is Emergency Medicine (copy Jan 8, 2001) and the file is Emergency Medicine.kno, rename the file to Emergency Medicine (copy Jan 8, 2001).kno (or rename the folder to Emergency Medicine). If the names do not match, SuperMemo will again recreate empty folders
  4. Open your restored collection and run File : Repair collection to make sure the collection does not include data discrepancies

Backing up Advanced English

From: Marcin Piekarniak
Country: Poland
Sent: Dec 2, 1997


How to easily back up Advanced English 97? In Advanced English 94 the entire system could be compressed to a 1.4 MB file!


If you wish, you can back up only the learning process. This way, only the data related to memorized items will be stored (not the items themselves). Use File : Export : Learning process to export the data. Later, upon reinstalling Advanced English 97, you can restore the learning process with File : Import : Learning process. See: Backup

Collection files missing


Carol M. asked:

What is the meaning of this message:

Collection files missing! Folder=C:\SUPERMEMO\SYSTEMS\BIO132_LEC_DIGESTIVE SYSTEM\ Try to restore files that you have moved or deleted


Your collection is incomplete. It is missing some essential files that can make recovery impossible.

The most frequent reason for this error is a mistake on the part of the user. SuperMemo collections are made of a *.KNO file and a folder with other essential files. Many users believe that the small KNO file contains all information and copy/backup only that single file. If you get the error as above, see if you have not separated the KNO file from its folder. Putting those two together will bring your collection back to life.

In your case, see if the file C:\SUPERMEMO\SYSTEMS\BIO132_LEC_DIGESTIVE SYSTEM.kno exists, if it is not empty, and if the folder C:\SUPERMEMO\SYSTEMS\BIO132_LEC_DIGESTIVE SYSTEM\ is not empty, and includes \REGISTRY\TEXT.PTR and \INFO\COMPON.DAT files.


SuperMemo always tries to restore missing files and attempts recovery in all conceivable scenarios. This is why SuperMemo collections often survive serious disk damage. However, in the past, users would often get confused when SuperMemo restored the entire empty collection from a lone KNO file. This is why, newer versions check for the presence of essential files that are needed for a collection to be meaningfully recoverable. Those files include the text registry (most collections contain texts used in learning), and compon.dat (collection without components is of little use).