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Contents : Technical reference : Advanced reference
Files and folders used by SuperMemo

These are the files used by a typical SuperMemo installation:

SuperMemo folder - usually c:\sm8, c:\sm98, c:\sm99, c:\sm2000, etc.

Most important fields of the KNO file

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

Frequently Asked Questions

Your collection can suddenly appear empty!
With luck, you can recover from "empty backup"!
Backing up Advanced English

(Marcin Piekarniak, Poland, 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!
You can backup the learning process only. This way only the data pertaining to items in the learning process will be stored (not items themselves). Use File : Tools : Export : Learning process to export the data. Later, upon reinstalling Advanced English 97, you can restore the learning process with File : Tools : Import : Learning process. See: Backup

(Michael Duggan, Canada, 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 always recommended to 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 (see: Files used by SuperMemo).
Some customers also fall victim of the following scenario:

  1. user moves the whole SuperMemo folder to a new location using Windows tools
  2. user starts sm2000.exe 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. User responds with Yes
  6. SuperMemo creates empty files with the old name
  7. User is convinced he lost his data while intact collections 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

(Przemek S, Poland, 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 just 20KB of data! 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 : Tools : Quick 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. burden.dat or sm8opt.dat). Make an inventory of all kno files (search for *.kno) and all SuperMemo collection folders (search for burden.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 on one of these files will restore the lost backup. Note that you can easily find empty collections by checking the size of burden.dat. This file contains repetitions and is zero-sized on collections with no learning process

(Richard D, USA, 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 which is just 20KB of data! 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.reg on all your hard disks (including backup drives, networks and CDRs)
    4. Sort text.reg files by size (the more work you put in the collection, the larger the file)
    5. You can view the content of text.reg and see if it corresponds with the material you put into your collection
    6. If you do not file the folder with the matching text.reg, 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.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

If you run into trouble in Step 4 (i.e. your collection does not recover properly), send this collection in the state from before the recovery to bugs(AT)supermemo(.)com

Disappearing material (#6428)
(hojinil, South Korea, 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. 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