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

Sort by
Subject
Level

Fundamental Computer Science Concepts & Algorithms

Classified in Computers

Written on in English with a size of 1.64 MB

Arithmetic Progressions (AP)

Sum of terms = n[(1st term + last term)]/2

Geometric Progressions (GP)

Sum of terms = [1st term(1 - quotientn)/(1 - quotient)] (Swap positions of 1 & quotient if quotient > 1)

Logarithms

  • loga(x/y) = logax - logay
  • logaxn = nlogax
  • logab = (logcb/logca)

Permutations

For a set of n objects: The total number of permutations is n!

For arranging 'r' objects from a set of 'n' objects: The number of permutations is nPr = n! / (n-r)!. (e.g., ways to arrange 3 objects from a set of 5 is 5 * 4 * 3, since there are 5 possibilities for the first object, followed by 4, then 3.)

Combinations

For selecting 'r' objects from a set of 'n' objects: The number of combinations is nCr = n! / (r! * (n-r)!). (Divide by r! since there are r! ways

... Continue reading "Fundamental Computer Science Concepts & Algorithms" »
Karma: 14%
Visits: 0

Understanding Binary Adders and Race Conditions in Flip-Flops

Classified in Computers

Written on in English with a size of 4.17 KB

Binary Parallel Adder

A binary parallel adder is a digital circuit that adds two binary numbers in parallel, meaning all bits are added simultaneously. It typically consists of full adders arranged in parallel, with each full adder adding corresponding bits from the two input numbers.

BCD Adder

A BCD (Binary Coded Decimal) adder is a specific type of binary parallel adder designed to add two BCD numbers. BCD numbers are decimal digits encoded in binary, where each decimal digit is represented by its 4-bit binary equivalent.

Truth Table for a 4-bit BCD Adder

Here's the truth table for a 4-bit BCD adder:


Diagram


In the truth table:

  • A3 A2 A1 A0 represents the first BCD number (A).
  • B3 B2 B1 B0 represents the second BCD number (B).
  • Cin represents the carry-
... Continue reading "Understanding Binary Adders and Race Conditions in Flip-Flops" »
Karma: 14%
Visits: 0

Essential Algorithms and Data Structures: A Quick Reference

Classified in Computers

Written on in English with a size of 580.94 KB

fUlQAAAABJRU5ErkJggg==

AOUNZyjQwEJMAAAAAElFTkSuQmCC

Essential Algorithms and Data Structures

Longest Increasing Subsequence (LIS):

  • Subproblem: dp[i] = length of LIS ending at index i
  • Recursion: dp[i] = max(dp[j] + 1 for j < i and arr[j] < arr[i])
  • Base case: dp[i] = 1 (every element is a subsequence of length 1)
  • Time Complexity: O(n^2), O(n log n) with binary search optimization.

Longest Alternating Subsequence (LAS):

  • Subproblem: dp[i][0] (increasing), dp[i][1] (decreasing)
  • Recursion: dp[i][0] = max(dp[j][1] + 1 for j < i and arr[j] < arr[i]), dp[i][1] = max(dp[j][0] + 1 for j < i and arr[j] > arr[i])
  • Base case: dp[0][0] = 1, dp[0][1] = 1
  • Time Complexity: O(n^2)

0/1 Knapsack Problem:

  • Subproblem: dp[i][w] = maximum value for the first i items and weight limit w
  • Recursion: dp[i][w] = max(
... Continue reading "Essential Algorithms and Data Structures: A Quick Reference" »
Karma: 14%
Visits: 0

Network Fundamentals: Protocols, Addressing, Security

Posted by Anonymous and classified in Computers

Written on in English with a size of 17.78 KB

TCP Reliable Transfer and Connection Management

TCP Reliable Transfer

  1. Sequence Numbers

    • Each byte of data is assigned a sequence number. This number is used by the receiver to correctly order the data and ensure there are no missing segments.

  2. Acknowledgements

    • The receiver sends back an ACK to the sender for the sequence number of the next expected byte. If the sender receives the ACK before its timer expires, it knows everything up to that byte was received correctly.

  3. Retransmission

    • If the ACK is not received before the timer expires, the sender retransmits the data.

TCP Connection Management

Managing a TCP connection begins with a three-way handshake, which establishes a connection before any actual data is transmitted.

Steps in Three-Way Handshake

  1. SYN
    • The
... Continue reading "Network Fundamentals: Protocols, Addressing, Security" »
Karma: 14%
Visits: 0

Sistema de Gestión de Usuarios con Java Web

Classified in Computers

Written on in English with a size of 21.85 KB

Archivos HTML del Frontend

INDEX.HTML: Menú Principal del Sistema

<!DOCTYPE html>
<html>
<head>
    <title>Menú Principal del Sistema</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <style>
        h2 { color: #789; font-size: 45px; }
        select { color: brown; font-size: 30px; }
        h3 { color: #8b4513; font-size: 30px; }
    </style>
</head>
<body>
    <h2>Menú de Opciones del Sistema</h2>
    <h3>Seleccione una opción:</h3>
    <ol>
        <li><a href="Registro.html">Registrar Usuario</a></li>
        <li><a href="Acceso.html">Acceso
... Continue reading "Sistema de Gestión de Usuarios con Java Web" »
Karma: 14%
Visits: 0

C++ Code Examples: Arithmetic Mean, Sum, Product, Square

Classified in Computers

Written on in English with a size of 1.55 KB

Arithmetic Mean

The following C++ code calculates the arithmetic mean of numbers from 1 to n:

int main() {
    int n;
    double suma = 0;
    cout << "Vnesi broj: ";
    cin >> n;
    if (n <= 0) {
        cout << "Brojot na elementi mora da bide pogolem od 0!" << endl;
        return 1;  
    }
    for (int i = 1; i <= n; i++) {
        suma += i;  
    }
    double sredina = suma / n;
    cout << "Aritmetichkata sredina na broevite od 1 do " << n << " e: " << sredina << endl;
    return 0;
}

Sum

The following C++ code calculates the sum of numbers from 1 to n:

int main() {
    int n, sum = 0;
    cout << "Vnesi broj n: ";
    cin >> n;
    for (int i = 1; i <= n; i++)
... Continue reading "C++ Code Examples: Arithmetic Mean, Sum, Product, Square" »
Karma: 14%
Visits: 0

Network Security & Configuration: Routing, VLANs, DHCP, and Attack Mitigation

Classified in Computers

Written on in English with a size of 2.38 KB

Router-on-a-Stick Inter-VLAN Routing

The router's port connecting to the LAN has multiple sub-interfaces, each the default gateway for a specific VLAN. For example, VLAN 10 traffic destined for VLAN 20 is first forwarded to VLAN 10's default gateway (the router sub-interface). The router then routes this traffic to VLAN 20's gateway (its corresponding sub-interface) and finally to the user in VLAN 20.

Why STP Is Needed for Redundant Ethernet LANs

  • Preventing Broadcast Storms: In redundant networks, frames can loop endlessly, exponentially increasing traffic. STP prevents this by disabling redundant paths, ensuring one active path between devices.
  • Ensuring MAC Address Table Consistency: Loops cause switches to receive the same frame on different
... Continue reading "Network Security & Configuration: Routing, VLANs, DHCP, and Attack Mitigation" »
Karma: 14%
Visits: 0

C Language Fundamentals: Output, Control Flow, Strings, and Sorting

Classified in Computers

Written on in English with a size of 22.92 KB

C printf Function: Format Specifiers Explained

The printf function in C is used to display formatted output to the standard output (usually the console). It allows programmers to control how data is presented by using **format specifiers**. Format specifiers are placeholders that define the type of data being printed and how it should be formatted. They begin with a % symbol, followed by a character that specifies the data type.

Role of Format Specifiers

Format specifiers serve two main purposes:

  1. Data Type Identification: They inform the printf function about the type of data being passed as an argument. For example, %d is used for integers, while %f is used for floating-point numbers.
  2. Formatting Control: They allow customization of how the data
... Continue reading "C Language Fundamentals: Output, Control Flow, Strings, and Sorting" »
Karma: 14%
Visits: 0

Essential Linux Commands & File System Structure

Classified in Computers

Written on in English with a size of 7.16 KB

Linux File System Structure: An archive of Linux is associated with 3 parts: superblock, inode table, and data blocks.

Network Ports: To see the ports assigned to services.

Display Active TCP/IP Connections: netstat -a

User Management:

  • Create password: passwd (user)
  • Add user to group: usermod -g group_name
  • Disable: 60001
  • Enable: 60002

Practical Commands:

Add User: adduser

  1. Change folder privileges: chmod
  2. Check privileges: ls -de (see if you changed privileges)
  1. Create a user: useradd newuser
    passwd newuser
  2. Create a directory: The command mkdir is used to create directories:
    mkdir mydirectory
  3. Create a report: ps -aux >> reporte.txt
  4. Directories associated with the user: -d dirname
  5. Changing permission: chmod 744 file.txt /file.txt
  6. Change owner: chown
    Entering
... Continue reading "Essential Linux Commands & File System Structure" »
Karma: 14%
Visits: 0

Shell script

Classified in Computers

Written on in English with a size of 2.47 KB

Ejercicio de descuentos:

#!/bin/bash

read -p "¿Desea el billete también de vuelta? (s/n): " idavuelta

until [ $idavuelta=="s" ] || [ $idavuelta=="n" ]; do

read -p "¿Desea el billete también de vuelta? (s/n): " idavuelta

done

read -p "¿Tiene carnet joven? (s/n): " carnetjoven

until [ $carnetjoven="s" ] || [ $carnetjoven="n" ]; do

read -p "¿Tiene carnet joven? (s/n): " carnetjoven

done

descuento=0 billete=20

if [ $idavuelta="s" ]; then

descuento=20

billete=" expr $billete \* 2'

fi

if [ $carnetjoven="s" ]j then

descuento=30

fi

costefinal=`expr $billete \* \( 100 - $descuento \) / 100`

echo "El precio final del billete es $costefinal"



Ejercicio de medias:

#!/bin/bash

acu=0

cont=0

read -p "Introduce un numero: " num

while [ $num -ne 0 ]; do

acu=`expr $acu + $num`

cont=... Continue reading "Shell script" »

Karma: 13%
Visits: 1,143