AddressBook Level 3 (AB3) is a desktop app for managing contacts, optimized for use via a Command Line Interface (CLI) while still having the benefits of a Graphical User Interface (GUI). If you can type fast, AB3 can get your contact management tasks done faster than traditional GUI apps.

Quick start

  1. Ensure you have Java 11 or above installed in your Computer.

  2. Download the latest addressbook.jar from here.

  3. Copy the file to the folder you want to use as the home folder for your AddressBook.

  4. Open a command terminal, cd into the folder you put the jar file in, and use the java -jar addressbook.jar command to run the application.
    A GUI similar to the below should appear in a few seconds. Note how the app contains some sample data.

  5. Type the command in the command box and press Enter to execute it. e.g. typing help and pressing Enter will open the help window.
    Some example commands you can try:

    • list : Lists all contacts.

    • add n/John Doe p/98765432 e/ a/John street, block 123, #01-01 : Adds a contact named John Doe to the Address Book.

    • delete 3 : Deletes the 3rd contact shown in the current list.

    • clear : Deletes all contacts.

    • exit : Exits the app.

  6. Refer to the Features below for details of each command.


:information_source: Notes about the command format:

  • Words in UPPER_CASE are the parameters to be supplied by the user.
    e.g. in add n/NAME, NAME is a parameter which can be used as add n/John Doe.

  • Items in square brackets are optional.
    e.g n/NAME [t/TAG] can be used as n/John Doe t/friend or as n/John Doe.

  • Items with ​ after them can be used multiple times including zero times.
    e.g. [t/TAG]…​ can be used as   (i.e. 0 times), t/friend, t/friend t/family etc.

  • Parameters can be in any order.
    e.g. if the command specifies n/NAME p/PHONE_NUMBER, p/PHONE_NUMBER n/NAME is also acceptable.

  • Extraneous parameters for commands that do not take in parameters (such as help, list, exit and clear) will be ignored.
    e.g. if the command specifies help 123, it will be interpreted as help.

  • If you are using a PDF version of this document, be careful when copying and pasting commands that span multiple lines as space characters surrounding line-breaks may be omitted when copied over to the application.

Viewing help : help

Shows a message explaning how to access the help page.

help message

Format: help

Adding a person: add

Adds a person to the address book.


:bulb: Tip: A person can have any number of tags (including 0)


  • add n/John Doe p/98765432 e/ a/John street, block 123, #01-01
  • add n/Betsy Crowe t/friend e/ a/Newgate Prison p/1234567 t/criminal

Listing all persons : list

Shows a list of all persons in the address book.

Format: list

Editing a person : edit

Edits an existing person in the address book.

Format: edit INDEX [n/NAME] [p/PHONE] [e/EMAIL] [a/ADDRESS] [t/TAG]…​

  • Edits the person at the specified INDEX. The index refers to the index number shown in the displayed person list. The index must be a positive integer 1, 2, 3, …​
  • At least one of the optional fields must be provided.
  • Existing values will be updated to the input values.
  • When editing tags, the existing tags of the person will be removed i.e adding of tags is not cumulative.
  • You can remove all the person’s tags by typing t/ without specifying any tags after it.


  • edit 1 p/91234567 e/ Edits the phone number and email address of the 1st person to be 91234567 and respectively.
  • edit 2 n/Betsy Crower t/ Edits the name of the 2nd person to be Betsy Crower and clears all existing tags.

Locating persons by name: find

Finds persons whose names contain any of the given keywords.


  • The search is case-insensitive. e.g hans will match Hans
  • The order of the keywords does not matter. e.g. Hans Bo will match Bo Hans
  • Only the name is searched.
  • Only full words will be matched e.g. Han will not match Hans
  • Persons matching at least one keyword will be returned (i.e. OR search). e.g. Hans Bo will return Hans Gruber, Bo Yang


  • find John returns john and John Doe
  • find alex david returns Alex Yeoh, David Li
    result for 'find alex david'

Deleting a person : delete

Deletes the specified person from the address book.

Format: delete INDEX

  • Deletes the person at the specified INDEX.
  • The index refers to the index number shown in the displayed person list.
  • The index must be a positive integer 1, 2, 3, …​


  • list followed by delete 2 deletes the 2nd person in the address book.
  • find Betsy followed by delete 1 deletes the 1st person in the results of the find command.

Clearing all entries : clear

Clears all entries from the address book.

Format: clear

Exiting the program : exit

Exits the program.

Format: exit

Saving the data

AddressBook data are saved in the hard disk automatically after any command that changes the data. There is no need to save manually.

Editing the data file

AddressBook data are saved automatically as a JSON file [JAR file location]/data/addressbook.json. Advanced users are welcome to update data directly by editing that data file.

:exclamation: Caution: If your changes to the data file makes its format invalid, AddressBook will discard all data and start with an empty data file at the next run. Hence, it is recommended to take a backup of the file before editing it.
Furthermore, certain edits can cause the AddressBook to behave in unexpected ways (e.g., if a value entered is outside of the acceptable range). Therefore, edit the data file only if you are confident that you can update it correctly.

Archiving data files [coming in v2.0]

Details coming soon …


Q: How do I transfer my data to another Computer?
A: Install the app in the other computer and overwrite the empty data file it creates with the file that contains the data of your previous AddressBook home folder.

Known issues

  1. When using multiple screens, if you move the application to a secondary screen, and later switch to using only the primary screen, the GUI will open off-screen. The remedy is to delete the preferences.json file created by the application before running the application again.

Command summary

Action Format, Examples
e.g., add n/James Ho p/22224444 e/ a/123, Clementi Rd, 1234665 t/friend t/colleague
Clear clear
Delete delete INDEX
e.g., delete 3
Edit edit INDEX [n/NAME] [p/PHONE_NUMBER] [e/EMAIL] [a/ADDRESS] [t/TAG]…​
e.g.,edit 2 n/James Lee e/
e.g., find James Jake
List list
Help help