Notes, summaries, assignments, exams, and problems for Computers

Four Servers Reside in the DMZ

• Mail
• WWW
• DNS
• Log Servers

DMZ Mail Server (a Separate Machine)

When an Email Message is Received from the Internet:

1. Reassembles the message.
2. Checks for malicious content.
3. Changes the addresses of the outer firewall (which is how the mail server is known to the outside world) to that of the internal mail server and forwards the mail to the internal mail server.

To Send a Message from the Internal Network to the Internet:

1. Reassembles the message.
2. Checks for malicious content (and maybe for proprietary information).
3. All internal addresses are replaced with "drib.org" (the name of the outside firewall).

DMZ WWW Server (a Separate Machine)

• Does not contact any servers or information sources on the internal network and it contains

Operating System Scheduling

1. The OS enables running multiple programs simultaneously. Several programs can reside in RAM concurrently, yet the CPU processes only one at a time. Only one process can be active at any given moment. CPUs are incredibly fast; even brief processing periods yield significant results. The OS determines the optimal method for switching between running, runnable, and waiting processes. It manages which process the CPU executes and distributes CPU access among processes. The task of determining when to switch processes is termed scheduling.

Disk Defragmentation

2. A disk defragmenter reorganizes files on a disk, ensuring they are stored contiguously. It arranges files on the disk into adjacent locations. This enhances... Continue reading "Understanding Operating Systems, Software, and Computer Hardware" »

Database Design Fundamentals

Key Concepts and Definitions

Data Type

The data type determines what field values are allowed and what other properties the field will have.

Saving a Table

You can specify a name for a table after you click the Save button on the Table Design toolbar.

Table Structure

The final step in the creation of a table is to save the table structure to disk.

Primary Key

A primary key uniquely identifies each record in a table.

Identifying Fields

When designing a database, you need to identify the fields that will be required.

Data Redundancy

Storing the same data field in multiple tables is called data redundancy.

Composite Key

A primary key that consists of more than one field is called a composite key.

Avoiding Data Redundancy

When designing... Continue reading "Database Design: Mastering Data Types, Keys, and Queries" »

Design patterns offer proven solutions to recurring software design challenges, promoting code reusability, maintainability, and efficiency. They can be categorized into three main types:

Behavioral Design Patterns

These patterns focus on communication and interaction between objects, enhancing flexibility. Examples include:

• Observer Pattern: Enables one-to-many dependencies, where changes in one object automatically notify dependent objects.
• Iterator Pattern: Provides sequential access to elements within a collection without exposing its underlying structure.

Creational Design Patterns

These patterns address object creation mechanisms, ensuring suitable instantiation processes. Examples include:

• Singleton Pattern: Restricts object creation to a single

Structural Design Patterns

Decorator - Adds additional functionality to a class

Adapter - 'adapts' one interface for a class into one that the client expects

Façade - creates a simplified interface from an existing one

Flyweight - A high quantity of objects share common properties to save space.

Bridge - decouples an abstraction from its implementation so that the two can vary independently.

Behavioral Design Patterns

Chain of Responsibility - Linked list of handlers

Command - Enables all the info for a request to be contained within a single object.

Interpreter - Developing domain specific languages

Iterator - Sequentially access elements of an aggregate object.

Mediator - Removes the need for classes to communicate with each other directly.

Observer... Continue reading "Structural and Behavioral Design Patterns in Software Development" »

Data Project Management: A Comprehensive Guide

Goal Setting: The Foundation of Project Planning

Every project requires a clear destination to determine its success. Goal setting is the first step in project planning, providing a roadmap for the project's journey.

Tools & Skills: Assessing Project Resources

The upper blocks of DR (Data Requirements) focus on evaluating the resources necessary for data project implementation. These resources include:

• Hard Resources: Data, software tools, processing
• Soft Resources: Skills, domain expertise, human resources for execution

Process & Value: Implementation and Delivery

The lower blocks of DR concentrate on project implementation and delivery. DR serves as a planning tool, helping project managers:

• Identify

Inserting Tables into Slides

In the Insert Object dialog box, click the Create From File option and click Browse to locate and choose the document or spreadsheet that contains the table. By default, the presentation software will insert the table. When you click OK, the entire document or spreadsheet is imported to your slide. Double-click the inserted text to remove extra text if the document contains more than the table. If you check the Link checkbox while inserting, after you update the table in the document or spreadsheet, then right click on the imported table in the presentation software, and select the option Update Link, the embedded table gets updated automatically. Drag and drop the table on the slide to position it.

Chart Design Principles

Convey... Continue reading "Embed and Link Objects in Presentations: Best Practices" »

1. What is recurrence for worst case of QuickSort and what is the time complexity in Worst case? Recurrence is T(n) = T(n-1) + O(n) and time complexity is O(n^2) 2. Suppose we have a O(n) time algorithm that finds median of an unsorted array. Now consider a QuickSort implementation where we first find median using the above algorithm, then use median as pivot. What will be the worst case time complexity of this modified QuickSort. O(nLogn)  3. Given an unsorted array. The array has this property that every element in array is at most k distance from its position in sorted array where k is a positive integer smaller than size of array. Which sorting algorithm can be easily modified for sorting this array and what is the obtainable time complexity?