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

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)

Operating Systems: System Calls and File Descriptors

int main(int argc, char *argv[]) {
  int fd = open(argv[1], O_WRONLY | O_CREAT | O_EXCL, 0644);
  if (fd == -1) {
    printf("There was a problem creating \"%s\"!\n", argv[1]);
    return 1;
  }
  close(fd);
  return 0;
}

void copyContents(int sourceFD, int destinationFD) {
  char buffer[kCopyIncrement];
  while (true) {
    ssize_t bytesRead = read(sourceFD,

Assembly Language Code Analysis and Solutions

Section 1: Instruction Correctness Check

.data

calculate WORD 100
wVal DWORD 2

Instructions:

1. mov bl, calculate
2. mov ax, wVal

Question 1: Are the above two instructions correct? If not, justify your claim. [2 marks]

Answer:

Both instructions are incorrect.

• For the mov operation, the operands must generally be of the same size.
• In instruction 1, bl is 8 bits (1 byte), but calculate is defined as a WORD (16 bits or 2 bytes). The operand sizes do not match.
• In instruction 2, ax is 16 bits (2 bytes), but wVal is defined as a DWORD (32 bits or 4 bytes). The operand sizes do not match.

Section 2: Loop Pseudo-code

Question 2: Write the pseudo-code for the loop that calculates the sum of the integers 3 + 2 + 1. [2 marks]

P1: Python String Manipulation Techniques

Demonstrating String Operations

s = "hello"
print(s.capitalize())
print(s.upper())
print(s.rjust(100))
print(s.center(100))
print(s.replace('l','(M)'))
print(s)
print("don't")

Indexing

a = 'symbiosis2024'
print(a[2])

Negative Indexing

print(a[-1])
print(a[-6])

Slicing

print(a[9:12])
print(a[9:])
print(a[9:-1])
print(a[:8])
print(a[-12:-1])

Stride [start index:end index:step size]

print(a[0:13:2])
print(a[0::2])

Concatenation

b = 'hello'
c = 'world'
d = b + c
print(d)
e = b + " " + c
print(e)

Repetition

f = a * 3
print(f)
g = "2024"
print(g * 2)
print(a + '2')

Reversing a String

print(a[::-1])

Split

h = "sspu"
print(h.split()) # Returns a list
i = "05/08/2024"
print(i.split("/"))
j = "14:20:25"
print(j.split("