==================================================== PASSWORD MANAGER - Documentation ==================================================== 1. SUPPORTED FUNCTIONALITY --------------------------- The application is a command-line password manager written in C that supports the following features: - Add a credential record The user enters a service name, username, and password. All three fields are encoded before being written to file. Empty fields are rejected. - List all saved entries Reads every record from passwords.txt, decodes them, and prints them to the screen in a numbered list. - Search by service name The user types a service name. The program scans all records and prints every entry whose service field matches exactly. - Delete an entry by service name The user types a service name. All records with that name are removed. The remaining records are written back to the file. - Persistent file storage All data is saved in passwords.txt so it is available across program runs. The file is created automatically on the first add. - Encoded storage Passwords, usernames, and service names are never stored as plain text. A Caesar shift of 7 is applied to every character before writing to the file. 2. HOW THE SOLUTION IS ORGANIZED ---------------------------------- Source file: password_manager.c Struct ------ Entry Stores one credential record with three fields: service[60], user[60], pass[60]. Constants --------- DATA_FILE the storage file name (passwords.txt) SHIFT the encoding shift value (7) MAX_RECORDS maximum entries that can be loaded at once (200) SERVICE_LEN, USER_LEN, PASS_LEN buffer sizes for each field Helper functions ---------------- flush_input() After reading a number with scanf, leftover characters stay in the input buffer. This function discards them so the next keyboard read works correctly. read_line(buf, limit) Reads one line of keyboard input using fgets and removes the newline character at the end. encode(s) Loops through a string and adds 7 to every character's ASCII value, making it unreadable in the file. decode(s) Loops through a string and subtracts 7 from every character's ASCII value, restoring the original text. print_divider() / print_entry(e) Display helpers that print a credential record inside a formatted box. File I/O functions ------------------ load_all(entries, max) Opens passwords.txt and reads every entry into an array of Entry structs. Each entry occupies three consecutive lines in the file (service, username, password). fscanf reads one line at a time using the format %59[^\n]\n, which reads up to 59 characters until the end of the line. Each field is decoded after reading so it is readable while the program is running. Returns the number of entries loaded. save_all(entries, count) Opens passwords.txt in write mode (overwriting it) and writes every entry in the array back to the file encoded. This is used by delete_entry: after removing the unwanted entries from the array, the remaining ones are written back. Encoding before writing ensures the file never contains plain text. A copy of each entry is used so the version in memory stays decoded. Menu functions -------------- add_entry() Opens passwords.txt in append mode, reads the three fields from the user, rejects blank fields, encodes all three, and writes each field on its own line. list_entries() Calls load_all to get all records, then prints each one using print_entry. search_entry() Calls load_all, then loops through every record comparing the service field to the search query using strcmp. Prints every match found. delete_entry() Calls load_all to get all records. Loops through them and separates matching entries (to be deleted) from non-matching ones (to be kept). Calls save_all with only the kept entries to overwrite the file. main() Runs an infinite loop that prints the menu, reads an integer choice with scanf, and calls the matching function. Exits on choice 5. Encoding algorithm ------------------ Every character in a string has 7 added to its ASCII value before being written to the file. To read it back, 7 is subtracted. This means no field in passwords.txt is ever stored as readable text. The shift of 7 applies to service name, username, and password equally. Storage format (three lines per entry) --------------------------------------- Each entry is stored as three consecutive lines: encodedService encodedUser encodedPass No separator character is used. Each field occupies its own line so there is no risk of an encoded character accidentally matching a separator. For example, with a shift of 7 the letter 'u' (ASCII 117) encodes to '|' (ASCII 124). If a pipe were used as a separator, a password containing 'u' would corrupt the file format. The three-line approach avoids this problem entirely. 3. TESTING ----------- Testing approach ---------------- The application was tested manually by running it, entering inputs for each feature, and checking that the printed output and contents of passwords.txt matched what was expected. Test cases ---------- Test 1: Add a single entry Steps: Choose 1. Enter service: gmail, username: alice@gmail.com, password: pass123 Expected: Prints "Entry saved." passwords.txt is created with three lines of encoded text (one per field). Result: PASS Test 2: Add multiple entries then list all Steps: Add a second entry: github / alice / abc456. Choose 2. Expected: Both entries shown decoded in the correct order. Result: PASS Test 3: Search for an existing service Steps: Choose 3. Enter: gmail Expected: Only the gmail entry is shown. github is not shown. Result: PASS Test 4: Search for a service that does not exist Steps: Choose 3. Enter: facebook Expected: Prints "No entries found for facebook." Result: PASS Test 5: Delete an existing entry Steps: Choose 4. Enter: gmail Expected: Prints "Deleted 1 entry/entries for gmail." Listing afterwards shows only the github entry. Result: PASS Test 6: Delete a service that does not exist Steps: Choose 4. Enter: twitter Expected: Prints "No entries found for twitter." passwords.txt is unchanged. Result: PASS Test 7: Add two entries with the same service name then delete Steps: Add two entries both with service: gmail. Choose 4, enter: gmail Expected: Prints "Deleted 2 entry/entries for gmail." List shows no gmail entries remaining. Result: PASS Test 8: List when no entries have been saved Steps: Delete passwords.txt, then choose 2. Expected: Prints "No entries stored yet." without crashing. Result: PASS Test 9: Enter a non-numeric menu choice Steps: Type: abc at the menu prompt. Expected: Prints "Please enter a number." and shows menu again. Result: PASS Test 10: Add entry with an empty field Steps: Choose 1. Press Enter immediately for service name. Expected: Prints "Fields cannot be empty." Nothing written to file. Result: PASS Test 11: passwords.txt does not contain plain text Steps: Add an entry with password: hello. Open passwords.txt. Expected: The word "hello" does not appear anywhere in the file. All fields appear as garbled characters. Result: PASS