Explanation

• Router: Connects two or more networks.
• Directs data packets to their correct destination.
• Selects the best route for data transmission.
• Connects a local network (LAN) to the internet.
• Works mainly at Layer 3 (Network Layer) of the OSI model.

Explanation

• 1 nanosecond = one billionth of a second.
• 1  ns = 10^-9 seconds.
• 1 microsecond = 1,000 nanoseconds.
• Computer memory access time is often measured in nanoseconds.

Explanation

• Registers hold data for the shortest duration during CPU processing.
• They are the fastest and smallest memory in the computer.
• Order: Register → Cache → RAM → Hard Disk.
• ~1 clock cycle (Fractions of a nanosecond)

Additional information:

• Fastest computer memory: Register
• Main working memory: RAM

Explanation

A document in Microsoft Word can be saved in three commonly taught ways.

1. File → Save → Saves the document.
2. Ctrl + S → Quick Save shortcut.
3. F12 → Opens the Save As dialog box.

Save → Updates the current file.

Save As → Saves with a new name, location, or format.

Explanation

• Hashing converts data into a fixed-length hash value.
• It helps verify data integrity by detecting changes.
• It is used to store passwords securely as hashes.
• Hashing is a one-way process; the original data is not normally recoverable from the hash.

Explanation

• A DoS attack floods a system or server with excessive traffic or requests.
• It makes the service slow or unavailable to legitimate users.
• DDoS (Distributed Denial-of-Service): Uses multiple devices to launch the attack.

Explanation

• SQL injection exploits unsanitized or improperly handled user input in database queries.
• Attackers manipulate SQL statements to access or modify data without authorization.
• Prevention: Use parameterized queries (prepared statements).

Explanation

• COUNT(*) counts all rows in a table.
• If the table is empty, it returns 0.
• It counts rows regardless of NULL values in individual columns.

Explanation

• DISTINCT returns only unique rows or values.
• It removes duplicate results from a query.
• It is used with the SELECT statement.

Explanation

• A subquery is a query written inside another SQL query.
• It is enclosed in parentheses ().
• It can be used with SELECT, INSERT, UPDATE, and DELETE statements.