Validation, authentication and file handling

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Validation

Validation checks that data entered is reasonable and sensible, but not necessarily correct. Types:
Range check: within limits (age 0-120). Length check: number of characters (password at least 8). Type check: correct data type (integer). Presence check: something has been entered. Format check: pattern (postcode). Lookup check: value is in a list.
Verification checks data was entered correctly: double entry (type twice) or visual check.

Validation checks

Authentication

Authentication checks evidence of a claimed identity, such as a password or fingerprint. Two-factor authentication combines different factor categories, for example a password and possession of a security key.
CAPTCHA checks whether activity is likely human rather than automated; it is not proof of identity.
Use long unique passwords or passphrases. Systems should store suitably salted password hashes rather than plaintext passwords.

Different authentication factors

Defensive design

Anticipate invalid input and misuse: validate against rules, handle errors, avoid hard-coded passwords and use meaningful names.
Sanitise or encode content appropriately for its destination. Use parameterised database queries; deleting suspicious characters is not a complete SQL-injection defence.

File handling

Programs can read from and write to text files so data persists after the program closes.
Steps: open the file (read, write or append), read/write data, close the file.
Example: file = OPEN("scores.txt") line = file.READLINE() file.CLOSE().

File-handling lifecycle

Why use files?

Store results, load configuration, and keep records.

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Câu hỏi luyện tập

Xem trước miễn phí — 8 trên 33 câu hỏi. Đăng ký để xem tất cả.

1.What is validation?
Easy
- Achecking input is sensible and acceptable
- Bchecking input is correct
- Cdeleting input
- Dencrypting input
2.What is authentication?
Easy
- Achecking a user's identity
- Bchecking data type
- Cchecking range
- Dchecking length
3.What does a length check do?
Easy
- Achecks the number of characters
- Bchecks the type
- Cchecks a list
- Dchecks a range
4.What does a type check do?
Easy
- Achecks data is the correct data type
- Bchecks the length
- Cchecks the format
- Dchecks the range
5.What does a lookup check do?
Easy
- Achecks the value is in a list
- Bchecks the length
- Cchecks the range
- Dchecks the presence
6.Which check would validate a postcode pattern?
Easy
- Aformat check
- Brange check
- Ctype check
- Dpresence check
7.What is verification?
Easy
- Achecking data was entered correctly
- Bchecking it is sensible
- Cchecking identity
- Dencrypting
8.What is double entry?
Easy
- Atyping data twice to check it matches
- Btyping it once
- Ccopying it
- Ddeleting it

Thêm câu hỏi

9.What is two-factor authentication?
Easy
- Ausing two different authentication factor categories
- Busing two passwords
- Chaving two users
- Dsaving two files
10.What is a biometric?
Easy
- Aa physical characteristic such as a fingerprint
- Ba password
- Ca code
- Da loop
11.What are the three main steps for file handling?
Easy
- Aopen, read or write, close
- Bcreate, delete, copy
- Cstart, stop, pause
- Dinput, output, loop
12.Why should a file be closed after use?
Medium
- Ato flush buffered writes and release file resources
- Bto delete all file contents
- Cto compress the file automatically
- Dto encrypt every record
13.What does append mode do?
Medium
- Aadds data to the end of a file
- Berases the file
- Creads the file
- Drenames the file
14.What does write mode usually do to existing data?
Medium
- Aoverwrites it
- Bkeeps it
- Ccopies it
- Dcompresses it
15.What is a CAPTCHA used for?
Medium
- Ato detect whether a user is a human
- Bto encrypt data
- Cto compress data
- Dto store passwords
16.Why are passwords hashed rather than stored plainly?
Medium
- Ato protect them if the database is stolen
- Bto make them shorter
- Cto make them visible
- Dto speed login
17.What is sanitising input?
Medium
- Acleaning input to remove harmful content
- Bdeleting it
- Ccompressing it
- Dencrypting it
18.A user enters "abc" for an age. Which validation check catches this?
Medium
- Atype check
- Brange check
- Cpresence check
- Dlookup check
19.An age field accepts integers from 0 to 120. A user enters 200. Which check rejects it?
Medium
- Arange check
- Btype check
- Cpresence check
- Dformat check
20.Why might validation pass but data still be wrong?
Medium
- Aan age of 25 may be valid but incorrect for the person
- Bvalidation always proves it
- Cno reason
- Dvalidation fails
21.What is a benefit of defensive design?
Medium
- Ait reduces the risk of misuse and input errors
- Bit guarantees every program is slower
- Cit removes all users
- Dit makes testing unnecessary
22.What does READLINE do?
Easy
- Areads one line from a file
- Bwrites a line
- Ccloses a file
- Ddeletes a file
23.What does WRITELINE do?
Easy
- Awrites a line to a file
- Breads a line
- Ccloses
- Dopens
24.What is a strong password?
Medium
- Aa long, unique password or passphrase
- Ba short common word
- Cthe same password on every account
- Da publicly known birthday
25.What is brute force?
Medium
- Atrying many passwords until one works
- Breading a file
- Ccompressing a file
- Dencrypting
26.Validation checks that data is sensible.
Easy
True or false?
27.A range check ensures a value is within limits.
Easy
True or false?
28.Validation guarantees data is accurate.
Easy
True or false?
29.Two-factor authentication combines evidence from two different factor categories.
Easy
True or false?
30.Files cannot store data after a program ends.
Medium
True or false?
31.Which are validation checks?
Medium
- Arange
- Blength
- Ctype
- Dpresence
- Ecompiling
32.Which are authentication methods?
Medium
- Apassword
- Bfingerprint
- Ctwo-factor
- DCAPTCHA
- Erange check
33.Explain the difference between validation and verification.
Medium

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