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

Architecture of 8051

1. CPU (Central Processing Unit)

• Controls all operations of the microcontroller.
• Performs arithmetic and logical operations.
• Executes program instructions.

2. RAM (Random Access Memory)

• Temporary storage for data.
• Stores variables and intermediate results.
• Data is lost when power is turned off.

3. ROM (Read Only Memory)

• Stores the program permanently.
• Retains data even when power is off.

4. Timers/Counters

• Used to generate time delays.
• Can count external events.
• 8051 has Timer 0 and Timer 1.

5. Ports

• Used for input and output operations.
• 8051 has 4 ports (P0, P1, P2, P3).
• Each port is 8-bit.

6. Serial Communication

• Used to exchange data with other devices.
• Uses TXD (Transmit) and RXD (Receive) pins.
• Supports serial data transmission and reception.

1. DES Structure

DES (Data Encryption Standard) is a symmetric key block cipher used for data encryption. It encrypts 64-bit plaintext using a 56-bit secret key.

DES uses a 16-round Feistel structure. The plaintext first undergoes initial permutation and is divided into left and right halves. In every round, the right half is processed using a round function and XORed with the left half. After 16 rounds, a final permutation is performed to generate the ciphertext.

Features

• 64-bit block size
• 56-bit key
• 16 rounds
• Uses Feistel structure

Advantages

• Simple implementation
• Efficient hardware encryption

Disadvantages

• Weak against brute-force attacks

2. AES Algorithm

AES (Advanced Encryption Standard) is a symmetric encryption algorithm used to secure digital communication.... Continue reading "Cryptography Fundamentals: DES, AES, RSA and Security" »

Primary Functions of an Operating System

An operating system (OS) is system software that acts as an interface between the user and the computer hardware. Its primary functions are:

• Process Management: Creation, scheduling, and termination of processes.
• Memory Management: Allocation and deallocation of memory.
• File Management: Organization, storage, and retrieval of files.
• Device/I-O Management: Controls peripheral devices.
• Security & Protection: Prevents unauthorized access.

What Is a Batch Processing System?

• A batch operating system groups similar jobs (with the same requirements) together and executes them as a single batch without user interaction.
• A resident monitor reads jobs sequentially from input and submits them to the CPU.
• Advantage: Less

Logistic Regression Implementation

1. Upload and Prepare Dataset

from google.colab import files
uploaded = files.upload()

2. Import Libraries

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
from sklearn.model_selection import train_test_split
from sklearn.preprocessing import StandardScaler
from sklearn.linear_model import LogisticRegression
from sklearn.metrics import confusion_matrix

3. Load and Split Data

data = pd.read_csv("Social_Network_Ads.csv")
X = data[['Age','EstimatedSalary']]
y = data['Purchased']
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.25, random_state=0)

4. Feature Scaling and Model Training

sc = StandardScaler()
X_train = sc.fit_transform(X_train)
X_test = sc.

1. Number Systems & Data Types

Question 1: What is the decimal equivalent of 0xBEEF?

• 48879

Question 2: What is the decimal number equivalent of the octal value 0465?

• 309

Question 3: What is the binary equivalent of decimal 135?

• 0b10000111

Question 4: What is the octal equivalent of 0x5EED?

• 057355

Question 5: What is the binary equivalent of 0xBEAD?

• 0b1011111010101101

Question 6: What is the range of an unsigned byte?

• 0 to 255

Question 7: What is the range of a signed word?

• 0x80000000 to 0x7FFFFFFF

[Exam 1] Question 8: What is the two's complement representation of -128 expressed as a signed half word?

• 0b1111111110000000

[Exam 1] Question 9: What is the Octal equivalent of Hex 0xDEAF?

• 0157257

[Exam 1] Question 10: Convert 0xA1A to decimal:

• 2586

[Exam 1] Question

1. MQTT Protocol and Architecture

MQTT is a lightweight messaging protocol designed for M2M IoT communication. It utilizes a publish–subscribe model, eliminating the need for direct device-to-device communication. Key features include low power consumption, low bandwidth usage, scalability, reliability (via QoS 0/1/2), and security (TLS). The architecture consists of a Client (publisher/subscriber device), a Broker (central server for message management, filtering, and routing), and a TCP/IP connection (CONNECT–CONNACK).

2. 6LoWPAN Working and Importance

6LoWPAN stands for IPv6 over low-power wireless personal area networks (IEEE 802.15.4). Its working mechanism involves header compression, packet fragmentation, an adaptation layer, mesh routing,... Continue reading "Essential IoT Wireless Communication Protocols Explained" »

Experiment 5: Customer Analytics Database

This Python experiment demonstrates the practical application of core data structures: Tuples, Lists, Sets, and Dictionaries to build a basic Customer Analytics System.

# Experiment Code:
# Tuple: Fixed dataset structure (immutable)
dataset_schema = ("CustomerID", "Name", "PurchaseAmount", "Segment")
# List: Stores purchase amounts (mutable, ordered)
purchase_amounts = []
# Set: Stores unique customer IDs
unique_customers = set()
# Dictionary: Stores complete customer records
customer_records = {}

while True:
    print("\n--- Menu Customer Analytics ---")
    print("1. Add Customer Data")
    print("2. View Purchase Amounts (List)")
    print("3. View Dataset Schema (Tuple)")
    print("4. View Unique

This program demonstrates the Banker's Algorithm, a classic deadlock avoidance strategy used in operating systems to manage resource allocation safely.

C Source Code

#include <stdio.h>

int n, m;
int alloc[10][10], max[10][10], need[10][10];
int avail[10], work[10], finish[10];

// Safety Algorithm
int checkSafety() {
    int seq[10], count = 0;

    for (int i = 0; i < n; i++) finish[i] = 0;
    for (int i = 0; i < m; i++) work[i] = avail[i];

    while (count < n) {
        int found = 0;
        for (int i = 0; i < n; i++) {
            if (!finish[i]) {
                int j;
                for (j = 0; j < m; j++) {
                    if (need[i][j] > work[j]) break;
                }
                if (j == m)

Class 11 Computer Science: Exam-Ready JavaScript and HTML5

Here are concise, exam-ready answers for your Class 11 Computer Science Question Bank:

1. What is Client-Side Scripting?

Client-side scripting refers to programs executed on the user's browser (the client) rather than the server. JavaScript is the most common example. It is used to create interactive web pages, validate forms, and reduce server load.

2. How to Declare a Variable in JavaScript

Variables are containers for storing data. In JavaScript, they are declared using three keywords:

• var: Used in older versions (function-scoped).
• let: Used for block-scoped variables (recommended).
• const: Used for variables whose values remain constant.

Example: let name = "Arsh";

3. JavaScript Data Types

JavaScript... Continue reading "Class 11 Computer Science: JavaScript and HTML5 Essentials" »

5G Enabling Technologies

5G is made possible by a combination of advanced radio, network, and computing technologies. These enabling technologies work together to deliver high data rates, ultra-low latency, massive connectivity, and high reliability.

1. Millimeter Wave (mmWave) Communication

5G uses high-frequency bands (typically 24 GHz–100 GHz) known as millimeter waves.

• Provides extremely high data rates
• Suitable for dense urban areas, stadiums, and hotspots
• Limited range, so it requires more base stations and small cells

2. Massive MIMO (Multiple Input Multiple Output)

Uses a large number of antennas at the base station.

• Increases spectral efficiency
• Supports multiple users simultaneously
• Improves data rates and coverage

3. Network Slicing

Divides... Continue reading "Core 5G Enabling Technologies and Sensor Network Architecture" »