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

🔎 Threat Actors & Their Attack Paths

Who is attacking?

Threat Actors are the people or groups launching attacks. Mnemonic: “NO HIS” (Nation-State, Organized Crime, Hacktivists, Insiders, Script Kiddies).

How do threats reach systems?

Threat Vectors are the attack paths used by threat actors. Mnemonic: “MFWDVN” (Messages, Files, Websites, Devices, Vendors, Networks).

Leap Year

#include <stdio.h>
int main() {
    int y;
    scanf("%d", &y);
    if ((y % 4 == 0 && y % 100 != 0) || y % 400 == 0)
        printf("Leap Year");
    else
        printf("Not Leap Year");
    return 0;
}

Simple Calculator Using Switch

#include <stdio.h>
int main() {
    char op;
    float a, b;
    scanf(" %c %f %f", &op, &a, &b);
    switch (op) {
        case '+': printf("%.2f", a + b); break;
        case '-': printf("%.2f", a - b); break;
        case '*': printf("%.2f", a * b); break;
        case '/':
            if (b != 0)
                printf("%.2f", a / b);
            else
                printf("Error");
            break;
        default: printf("Invalid Operator");
    }
    return

Postfix evaluation 

#include<stdio.H>
int stack[20];
int top = -1;

void push(int x)
{
    stack[++top] = x;
}

int pop()
{
    return stack[top--];
}

int main()
{
    char exp[20];
    char *e;
    int n1,n2,n3,num;
    printf("Enter the expression :: ");
    scanf("%s",exp);
    e = exp;
    while(*e != '\0')
    {
        if(isdigit(*e))
        {
            num = *e - 48;
            push(num);
        }
        else
        {
            n1 = pop();
            n2 = pop();
            switch(*e)
            {
            case '+':
            {
                n3 = n1 + n2;
                break;
            }
            case '-':
            {
 ... Continue reading "Ec lab" »

FCFS and SJF CPU Scheduling C Program Example

Corrected and formatted C source code for FCFS and SJF scheduling.

FCFS Scheduling C Implementation

#include <stdio.h>

int FCFS() {
    int bt[15], n, i, wt[15];
    float twt = 0, tat = 0, att, awt;
    printf("\nTHE FCFS SCHEDULING\n");
    printf("Enter the number of processes: ");
    scanf("%d", &n);
    printf("Enter burst time of all the processes:\n");
    for (i = 0; i < n; i++) {
        printf("P%d: ", i + 1);
        scanf("%d", &bt[i]);
    }

    wt[0] = 0;
    // for calculating waiting time of each process
    for (i = 1; i < n; i++)
        wt[i] = bt[i - 1] + wt[i - 1];

    printf("ProcessID\tBurstTime\tWaitingTime\tTurn Around Time\n");
    for (i = 0; i <

Addition of Two Numbers

<?php
if(isset($_POST['n1']) && isset($_POST['n2'])){
    $n1 = $_POST['n1'];
    $n2 = $_POST['n2'];
    $res = $n1 + $n2;
    echo "<h3>User Input Numbers:</h3>";
    echo "First Number = $n1 <br>";
    echo "Second Number = $n2 <br>";
    echo "Sum = $res";
}
?>

Enter Two Numbers:

PHP Conditional, Loops and Arrays Example

<?php
echo "<h3>Loop Example (1 to 5):</h3>";
for($i=1;$i<=5;$i++){
    echo "Number: $i <br>";
}
echo "<h3>Array Example:</h3>";
$fruits = array("Apple","Banana","Mango","Orange");
foreach($fruits as $f){
    echo "$f<br>";
}
?>

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JDBC Driver Types

Type 1: JDBC-ODBC Bridge

• Converts JDBC calls to ODBC
• ❌ Slow, platform dependent, and obsolete

Type 2: Native API Driver

• Uses database-specific native libraries
• ⚠️ Faster than Type 1 but platform dependent

Type 3: Network Protocol Driver

• Uses middleware server to connect
• 🌐 Platform independent but slower due to network

Type 4: Thin Driver

• Directly connects to database using pure Java
• ✅ Fast, platform independent, and most used

Tags in JSP

1. Directive Tags

• Provide instructions to the JSP container
• Syntax: <%@ ... %>
• Example: page, include, taglib

2. Scripting Tags

• Scriptlet Tag: Write Java code <% ... %>
• Expression Tag: Display output <%= ... %>
• Declaration Tag: Declare variables or methods <%! ... %>

3. Action

Tile Sequence Validation Logic

The following function determines if a sequence of tiles is valid by checking their compatibility and adjusting their orientation if necessary.

def is_valid_sequence(seq: list[Tile]) -> bool:
    if len(seq) < 2:
        res = True
    else:
        if not are_compatible(seq[0], seq[1]):
            seq[0] = seq[0][1], seq[0][0]
        i = 1
        while i < len(seq) and are_compatible(seq[i - 1], seq[i]):
            if seq[i - 1][1] != seq[i][0]:
                seq[i] = seq[i][1], seq[i][0]
            i += 1
        res = i == len(seq)
    return res

Square-Free Number Verification

This function checks if a positive integer is square-free, meaning no prime factor has an exponent greater than one.

def

Basic Protocol Filters

Use these filters to quickly isolate traffic based on common protocols:

• arp (Address Resolution Protocol)
• dns (Domain Name System)
• http (Hypertext Transfer Protocol)
• https (HTTP Secure)
• icmp (Internet Control Message Protocol)
• ip (Internet Protocol)
• ipv6 (Internet Protocol Version 6)
• ntp (Network Time Protocol)
• smtp (Simple Mail Transfer Protocol)
• ftp (File Transfer Protocol)
• ssh (Secure Shell)
• tls (Transport Layer Security)
• udp (User Datagram Protocol)
• tcp (Transmission Control Protocol)
• dhcp (Dynamic Host Configuration Protocol)
• bootp (Bootstrap Protocol)
• radius (Remote Authentication Dial-In User Service)
• snmp (Simple Network Management Protocol)
• kerberos
• smb (Server Message Block)
• nbns (NetBIOS Name Service)
• nbss (NetBIOS Session Service)