DESCO
Post: Sub-Assistant Engineer
Exam Date: 20.6.2025
Exam Taker: BUET
1.Explain with proper example of singly linked list.
Singly Linked List
A singly linked list is a linear collection of data items called nodes, where each node is divided into two parts.
- Data
- Link
- The first node has a special name called HEAD.
- The data part stores the data item.
- The link part stores the address of the next node.
- The last node is called the tail node.
- The linked list starts with a special pointer called the HEAD pointer and terminates with a NULL pointer.
Singly Linked List
Singly linked list হলো একটি linear collection of data items, যেগুলোকে node বলা হয়। প্রতিটি node দুইটি অংশে বিভক্ত থাকে।
- Data
- Link
- প্রথম node-টির একটি বিশেষ নাম রয়েছে, যাকে HEAD বলা হয়।
- Data part-এ data item store করা হয়।
- Link part-এ পরবর্তী node-এর address store করা হয়।
- শেষ node-টিকে tail node বলা হয়।
- Linked list একটি বিশেষ pointer দিয়ে শুরু হয় যাকে HEAD pointer বলা হয় এবং এটি NULL pointer-এ শেষ হয়।
struct node { int data; struct node *next; };
2. What is CLI?
3. What is OSPF? Briefly explain.
4. State the working protocol of VRRP.
5. Write JavaScript code to check NID validity.
function isValidBDNID(nid) {
// Remove extra spaces
nid = nid.trim();
// Check if contains only digits and valid length (10, 13, or 17)
if (!/^\d{10}$|^\d{13}$|^\d{17}$/.test(nid)) {
return false;
}
// If 17-digit Smart NID, validate birth year (first 4 digits)
if (nid.length === 17) {
const year = parseInt(nid.substring(0, 4), 10);
const currentYear = new Date().getFullYear();
if (year < 1900 || year > currentYear) {
return false;
}
}
return true;
}
// Example
let nid = "19981234567890123";
if (isValidBDNID(nid)) {
console.log("Valid NID");
} else {
console.log("Invalid NID");
}
6.Find out the network address and broadcast address of the address: 192.168.0.0/28.
Given Address: 192.168.0.0/28
Step 1: Subnet Mask
/28 means 28 bits for network.
Subnet Mask = 255.255.255.240
Block Size = 256 − 240 = 16
Step 2: Network Address (NA)
Since the given IP is 192.168.0.0 and /28 creates blocks of 16,
The first subnet range is:
192.168.0.0 – 192.168.0.15
Network Address (NA): 192.168.0.0
Step 3: Broadcast Address (BA)
Broadcast Address is the last address in the subnet range.
Broadcast Address (BA): 192.168.0.15
Valid Host Range:
Minimum Host = 192.168.0.1
Maximum Host = 192.168.0.14
Total Usable Hosts = 14
Step 1: Subnet Mask
/28 means 28 bits for network.
Subnet Mask = 255.255.255.240
Block Size = 256 − 240 = 16
Step 2: Network Address (NA)
Since the given IP is 192.168.0.0 and /28 creates blocks of 16,
The first subnet range is:
192.168.0.0 – 192.168.0.15
Network Address (NA): 192.168.0.0
Step 3: Broadcast Address (BA)
Broadcast Address is the last address in the subnet range.
Broadcast Address (BA): 192.168.0.15
Valid Host Range:
Minimum Host = 192.168.0.1
Maximum Host = 192.168.0.14
Total Usable Hosts = 14
7. Differentiate between Load Testing and Stress Testing.
8. What are CSRF and XSS?
9. Consider a Student Table like (StudentID, StudentName, Age, Department) now write below queries:
i) Show only specific department students.
ii) All students age highest to lowest.
iii) Student numbers in each department.
i) Show only specific department students.
ii) All students age highest to lowest.
iii) Student numbers in each department.
-- i) Show only specific department students
SELECT *
FROM Student
WHERE Department = 'CSE';
-- ii) All students age highest to lowest
SELECT *
FROM Student
ORDER BY Age DESC;
-- iii) Student numbers in each department
SELECT Department, COUNT(*) AS TotalStudents
FROM Student
GROUP BY Department;
