Operating Systems

Process State Models

The three-state model consists of Ready, Running, and Blocked.

The five-state model expands on this by including New and Terminated states.

Computer Networking

IPv4 vs. IPv6 Distinctions

• Address Length: IPv4 uses 32-bit addresses, whereas IPv6 utilizes 128-bit addresses.
• Delimiters: IPv4 separates segments with periods (.), while IPv6 uses colons (:).
• Representation: IPv4 is expressed in decimal notation, whereas IPv6 is written in hexadecimal.

Software Engineering

Black-box vs. White-box Testing Evaluation

• Black-box Testing: Simple and efficient to execute. However, it cannot guarantee complete code coverage, and automated test scripts typically have low reusability.
• White-box Testing: Provides thorough coverage of internal logic. The primary drawback is the significant human effort and time required to implement.

Databases

Index Categorization

Common index types include Standard, Unique, Primary, Composite, and Full-text indexes.

Detailed Explanation of Indexes

Consider a table named employees with the following columns: emp_id, full_name, ssn, age, sex.

Index naming convention: use lowercase letters. Standard indexes should be prefixed with idx_ followed by the table and column name. Unique indexes should be prefixed with uniq_.

1. Standard Index: The most fundamental index type without constraints. It permits null values and duplicate entries, serving primarily to accelerate query performance.

CREATE INDEX idx_employees_full_name ON employees (full_name);

2. Unique Index: Functions similarly to a standard index but strictly enforces uniqueness for all values in the indexed column (null values may be allowed depending on the DBMS). It boosts retrieval speed while preserving data integrity.

CREATE UNIQUE INDEX uniq_employees_ssn ON employees (ssn);