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

VHDL Flip-Flop Implementations

This section demonstrates various VHDL implementations of flip-flops and latches, showcasing different clocking, clear, preset, and load mechanisms.

entity reginf is
    port (
        d, clk, clr, pre, load, data : in  std_logic;
        q1, q2, q3, q4, q5, q6, q7   : out std_logic
    );
end reginf;

architecture rtl of reginf is
begin

Active High Clock D-Latch

A simple D-latch sensitive to the rising edge of the clock.

    -- D-latch with active high clock
    process
    begin
        wait until clk='1';
        q1 <= d;
    end process;

Active Low Clock D-Latch

A D-latch sensitive to the falling edge of the clock.

    -- D-latch with active low clock
    process
    begin
        wait until clk='0';

Write C++/Java program to draw 3-D cube and perform following transformations on it using OpenGL.

Scaling

#include // Include the GLUT header file

void display (void) {

glClearColor(0.0f, 0.0f, 1.0f, 1.0f); // Clear the background of our window to blue

glClear(GL_COLOR_BUFFER_BIT); // Clear the colour buffer (more buffers later on)

glLoadIdentity(); // Load the Identity Matrix to reset our drawing locations

glTranslatef(0.3f, 0.3f,-6.0f); // Push everything 5 units back into the scene, otherwise we won't see the primitive

//glScalef(0.5f, 1.0f, 2.0f); // Make the shape half as wide, the same height and twice as deep

glutWireCube(2.0f); // Render the primitive

glLoadIdentity(); // Load the Identity Matrix to reset our drawing locations

glTranslatef(0.0f,... Continue reading "3-D Cube Transformations in OpenGL" »

Different Means of Storing Data

• Regular Table
• Partitioned Table
• Index-Organized Table
• Clustered Table

Regular Table

A regular table, generally referred to as a 'table', is the most commonly used form of storing user data. The database administrator has very limited control over the distribution of rows in an un-clustered table. Rows can be stored in any order depending on the activity on the table.

Partitioned Table

A partitioned table enables the building of scalable applications. It has one or more partitions, each of which stores rows that have been partitioned using range partitioning, hash partitioning, composite partitioning, or list partitioning. Partitions are useful for large tables that can be queried or manipulated using several processes... Continue reading "Methods for Storing Data in a Database" »

Mobile Development: The Viewport Meta Tag

The viewport meta tag is crucial for responsive web design on mobile devices. It controls how the browser displays a webpage on different screen sizes. Here's a breakdown of its key attributes:

Key Attributes

• width: Defines the viewport width. Typically set to device-width, which matches the device's screen width.
• initial-scale: Sets the initial zoom level. A value of 1 ensures the webpage is displayed at 100% zoom initially.
• user-scalable: A boolean attribute. Setting it to no prevents users from zooming in or out.

**CIA Triad: Core Security Principles**

The CIA Triad consists of Confidentiality, Integrity, and Availability. These are the fundamental goals of information security.

**Threat Modeling: Proactive Security**

Threat modeling involves system decomposition and emphasizes security by design.

**Kerckhoffs's Principle: System Security**

Kerckhoffs's Principle states that:

1. Security should not depend on the secrecy of the system's design, but only on the secrecy of the key.
2. The system should be usable.
3. Keys must be easy to change.

**One-Time Pad: Unbreakable Encryption**

A One-Time Pad is an algorithm that XORs the message with a randomly generated key of equal length. It is secure if:

1. The key is truly random.
2. The key is as long as the message.
3. Each key is used

Bit stuffing and destuffing are crucial techniques used in data link layer protocols to ensure reliable data transmission. They prevent sequences of data bits from being misinterpreted as control characters or flags, especially when the data itself contains patterns identical to these control sequences.

What is Bit Stuffing?

Bit stuffing is the process of adding one or more extra bits into a data stream to break up a sequence of identical bits that might otherwise be misinterpreted as a control signal. For example, in protocols like HDLC, a flag sequence (01111110) is used to mark the beginning and end of a frame. To prevent the actual data from containing this sequence, a '0' bit is stuffed after every five consecutive '1's in the data stream.... Continue reading "C Program for Bit Stuffing and Destuffing" »

Understanding Computer Networks

• A computer network is the interconnection of multiple devices, generally termed as hosts, connected using multiple paths for the purpose of receiving data or media.
• Connected devices share information and resources.
• The channel or line is where this information is transmitted.

Computer Network Classifications

Networks can be classified in several ways:

1. By Size: The most common classification.
2. By Property
3. By Connection Method
4. By Topology

1. Network Classification by Size

• LAN (Local Area Network): Maximum of a building. The most frequent type, common in most offices.
• MAN (Metropolitan Area Network): Maximum of a city, connecting different buildings.
• WAN (Wide Area Network): Connects devices from different cities or even countries.

Scene 1:

• Everyone shows up in a round table with computers thinking on what is the new game they will create.

• Poster: Brainstorm of ideas

• Carla: What game should we create now?

• Andrea: We can create a city!

• Bernardo: Yes! Let’s create a game that allows creating and simulating the life of your own avatar.

• Ines: That will be perfect! We can design clothes and accessories for the avatars

• Cuesta: That is a great idea, and it will not take too much time to code.

• Carla: We can also adapt the game so people can play using their smartphones.

• Everyone: Great let's call it... BIM’S!

Scene 2:

• Cuesta: You sit down in front of a computer and start typing codes. Let’s start with the coding

  • Question to Bernardo: Bernardo, do you remember the coding of how to make

CIA Triad

The CIA Triad consists of Confidentiality, Integrity, and Availability. Related concepts include Authentication, Accountability, and Auditability.

Types of Harm

• Interception
• Interruption
• Modification
• Fabrication

Web Technologies

HTML

• GET: Embeds parameters into the URL.
• POST: Sends data directly to the server; more secure.

PHP

• PUT: Used to create or replace a file at the specified URL. Sends data like POST, more suitable for uploading files.

Penetration Testing

5 Steps to Penetration Testing:

1. Reconnaissance
2. Scanning
3. Gaining Access
4. Maintaining Access
5. Clearing Tracks

Security Controls

• Prevention: Outright stopping an attack.
• Deterrence: Making an attack harder.
• Deflection: Making a target less attractive.
• Mitigation: Lessening the harm.
• Detection: Identifying