Notes, abstracts, papers, exams and problems of Computers

Nmap Options

-PE: Quickly check if host is up.

-sn: Disable port scanning (host discovery).

-n: Disables DNS resolution (checks IP online without looking up hostnames).

-O: OS detection.

-A: OS detection, Version detection, Script scanning, traceroute.

-sV: Service detection (banner info, version).

-vV: Provides verbose output.

-sC: Scan with default scripts for additional info gathering.

--min-rate=5000: Ensures scan sends at least 5k packets per second.

nmap --script smb-enum-shares.nse -p 445 (ip): List shares and their properties.

To see scripts starting with X: ls /path/X

To execute script with script tracing: sudo nmap -script=smb-os-discovery -script-trace target_ip

To enumerate the SMB share files: sudo nmap -script=smb-enum-shares target_ip

Vulnerability... Continue reading "Nmap, Netcat, and Metasploit Commands Cheat Sheet" »

Digital Logic Circuits

Flip-Flops

Clocked RS Flip-Flop Drawbacks

Clocked RS flip-flops have some drawbacks, such as susceptibility to race conditions, where the output can become unpredictable if the inputs change too close to the clock edge. They also require careful handling of the inputs to avoid metastability issues, which can lead to incorrect output states. Additionally, they can have higher power consumption compared to other flip-flop types due to the need for a clock signal.

JK Flip-Flop Operation

Content about JK Flip-Flop operation, characteristic table, characteristics equation, circuit diagram, and timing diagram would be added here.

Magnitude Comparator

What is a Magnitude Comparator?

A magnitude comparator is a digital circuit that compares... Continue reading "Digital Logic Circuits: Flip-Flops, Comparators, Decoders, and Registers" »

Lecture 2: Dynamic Dispatch and Interfaces

• Dynamic Dispatch: The process of selecting which implementation of a polymorphic operation to call at runtime.
• Interface: Calling a method that is not in the interface will cause a compilation error.

Lecture 3: N/A

Lecture 4: Method Contracts, Exceptions, and Unit Testing

• Method Contract: Should define pre/post conditions and exceptional behavior. The client is to blame if the precondition is not met, and the service is to blame if the postcondition is not met. Exceptional behavior specifies what the code will do if a precondition is violated.
• Exception: Runtime exception (unchecked) and IO exception (checked). The IO exception must be caught; otherwise, the code won't compile.
• Unit Test: Test boundary

C++ Priority Queue Implementation

This document provides a C++ implementation of a priority queue using a heap data structure. The code includes the class definition, member functions, and supporting utilities.

Priority Queue Class Definition

#ifndef priority_queue_h_
#define priority_queue_h_

#include <iostream>
#include <vector>
#include <cassert>

template <class T>
class priority_queue {
private:
    std::vector<T> m_heap;

public:
    priority_queue() {}

    priority_queue(std::vector<T> const& values)
    {
        m_heap = values;
        for (int i = 0; i < m_heap.size(); i++){
            percolate_down(i);
            for (int j = i; j < m_heap.size(); j++){
                percolate_down(

What is an Exception?

Answer: An exception in Python is an error that occurs during program execution, disrupting the normal flow of instructions. Instead of crashing, the program can "catch" the exception and handle it gracefully using try and except blocks. Common exceptions include ZeroDivisionError, IndexError, and FileNotFoundError. You can also define custom exceptions. The finally block can be used for cleanup actions, ensuring certain code runs regardless of whether an exception was raised.

Different Modes of Opening a File

Answer: Different Modes of Opening a File

1. Read Mode ('r')

• Purpose: Opens a file for reading.
• Behavior:
  • The file pointer is placed at the beginning of the file.
  • If the file does not exist, a FileNotFoundError is raised.

Button Click Action Events

import java.awt.*;

import java.awt.event.*;

public class ButtonClickActionEvents

{

public static void main(String args[])

{

Frame f=new Frame("Button Event");

Label l=new Label("DETAILS OF PARENTS");

l.setFont(new Font("Calibri",Font.BOLD, 16));

Label nl=new Label();

Label dl=new Label();

Label al=new Label();

l.setBounds(20,20,500,50);

nl.setBounds(20,110,500,30);

dl.setBounds(20,150,500,30);

al.setBounds(20,190,500,30);

Button mb=new Button("Mother");

mb.setBounds(20,70,50,30);

mb.addActionListener(new ActionListener()

{

public void actionPerformed(ActionEvent e)

{

nl.setText("NAME: " + "Aishwarya");

dl.setText("DESIGNATION: " + "Professor");

al.setText("AGE: " + "42");

}

});

Button fb=new Button("Father");

fb.setBounds(80,70,50,30);

fb.addActionListener(

Tokens

In programming, a token is the smallest meaningful element in code. They are the building blocks of a language's syntax. Common token types include:

• Keywords: Reserved words like if, else, while, and int (for declaring integers).
• Identifiers: Names given to elements like variables (e.g., sum), functions, and arrays.
• Constants: Unchanging values during program execution (e.g., 3.14 for pi).
• Operators: Symbols for mathematical or logical operations (e.g., + for addition).
• Separators: Punctuation like commas (,), semicolons (;), and braces ({}).

Example: int sum = 10 + 5;

In this line, int is a keyword, sum is an identifier, = is an operator, 10 and 5 are constants, and ; is a separator.

Arithmetic Operators

C has nine arithmetic operators for basic... Continue reading "C Programming: Tokens, Operators, and Logic" »