Database Concepts: Terms and Definitions
Defining a Tuple
A tuple is a single row in a table in the relational model of a database. It represents a set of related data values, where each value is associated with a column or attribute. For example, in a table of employees, one row (or tuple) might contain the details of one employee.
Explaining the Outer Join Operation
An outer join is a type of join in SQL that returns all the rows from one table and the matching rows from the other table. If there is no match, the result will include NULL
Understanding Mechanical and Electromagnetic Waves, Telecommunications, and Computer Peripherals
Mechanical and Electromagnetic Waves
Mechanical waves require a material medium to propagate. For example, water waves are produced by the impact of an object. Electromagnetic waves can propagate through a vacuum and material means. In 1887, the German physicist Heinrich Hertz was the first to produce and detect them.
Electromagnetic Spectrum
The electromagnetic spectrum is the set of electromagnetic waves of all possible wavelengths.
Telecommunications
Electric Telegraph
The electric telegraph used long
Read MoreDatabase Indexing Techniques: Types and Structures
Database Indexing Techniques
We know that data is stored in the form of records. Every record has a key field, which helps it to be recognized uniquely.
Indexing is a data structure technique to efficiently retrieve records from the database files based on some attributes on which the indexing has been done. Indexing in database systems is similar to what we see in books.
Indexing is defined based on its indexing attributes. Indexing can be of the following types:
Primary Index: A primary index is defined
Real-Time Systems Scheduling and Process Management
Soft Real-Time System Scheduling
A soft real-time system has four periodic events with periods of 50, 100, 200, and 250 msec each. Suppose that the four events require 35, 20, 10, and x msec of CPU time, respectively. What is the largest value of x for which the system is schedulable?
The fraction of the CPU used is 35/50 + 20/100 + 10/200 + x/250. To be schedulable, this must be less than 1. Thus x must be less than 12.5 msec.
Real-Time System Schedulability Analysis
A real-time system needs to handle
Read MoreUnderstanding PC Components: Motherboard, RAM, CPU, PSU
Understanding PC Components
Motherboard
The motherboard is a printed circuit card central to the computer that contains the microprocessor, RAM, support circuitry, the ROM, and special slots that allow the connection of additional card adapters.
Chipset
The chipset is responsible for controlling determined functions of a computer. It controls data, instructions, and control signals between the CPU, memory, and bus. It manages data transfer between the CPU, memory, and peripherals and also supports the
Read MoreMicroprocessor Buses: Types, Functions, and Connections
A microprocessor bus is a common set of power lines that connects all devices and computer components. Circuit loads are observed in these lines to identify the data and respond when your ID is transmitted. Then, they begin to transmit or receive data in another set of cables. This transport is the means by which data travel and may have the following characteristics:
- Data Path Width: The number of bits that can be carried simultaneously.
- Clock Cycle Speed: The number of data groups per second that