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

Understanding Network Fundamentals

What Is a Router?

A router is a networking device that connects two or more networks and forwards data packets between them based on their IP addresses. It determines the best path for data to travel across networks.

Understanding SSH (Secure Shell)

SSH (Secure Shell) is a network protocol used to securely access and manage remote computers over an unsecured network. It encrypts the communication between client and server to ensure security.

What Are IEEE Standards?

IEEE Standards are technical standards developed by the Institute of Electrical and Electronics Engineers for designing and developing hardware, software, and networking technologies to ensure compatibility and interoperability (e.g., IEEE 802 standards... Continue reading "Essential Networking Concepts: Routers, SSH, and IPv4" »

Q1. Inheritance in Java (10 Marks)

Inheritance is an important feature of object-oriented programming that allows one class to acquire the properties and methods of another class. The class that gives its features is called the parent class or superclass, and the class that receives them is called the child class or subclass. In Java, inheritance is implemented using the extends keyword.

There are three main types of inheritance in Java:
(1) Single-level inheritance – one parent and one child class.
(2) Multilevel inheritance – one class inherits another, and another class further inherits it.
(3) Hierarchical inheritance – one parent class is inherited by multiple child classes.

Java does not support multiple inheritance using classes to... Continue reading "Core Java Concepts: Inheritance, Polymorphism & OOP" »

Algorithms

Algorithms involve inputs, instructions, outputs, and a purpose.

Instruction Types

• Instruction
• Decision
• Loop
• Variable
• Function

Python Basics

Comments

Comments explain what code is for, intended for human readers.

Variables

Storing a value in a variable is called assignment. It's best practice not to use generic names.

Calculations (Operators)

• + : Addition
• - : Subtraction
• * : Multiplication
• / : Division
• // : Integer Division (e.g., 6 // 4 = 1)
• % : Remainder / Modulo (e.g., 6 % 4 = 2)
• ** : Exponentiation

mass_in_kg = 15

weight_in_pounds = mass_in_kg * 2.2

print('the weight in pounds is: ', weight_in_pounds)

user_name = input("enter your user name: ")

print('hello', user_name)

Data Types

• int: Integer numbers (e.g., -1, 0, 2, 1000)
• float: Floating-point (real)

Syntax-Directed Translation Schemes (SDTS)

A possible Syntax-Directed Translation Scheme (SDTS) uses the attribute val to store the value of each non-terminal.

• E → E₁ + T { E.val = E₁.val + T.val }
• E → T { E.val = T.val }
• T → T₁ * F { T.val = T₁.val * F.val }
• T → F { T.val = F.val }
• F → num { F.val = num.value }

Bottom-Up Evaluation of 3 + 2 * 4

Evaluation using SDTS (bottom-up):

• F → num(4): F.val = 4
• F → num(2): F.val = 2
• F → num(3): F.val = 3
• T → F (for num(2)): T.val = F.val = 2
• T → T * F: T.val = T.val (from num(2)) * F.val (from num(4)) = 2 * 4 = 8
• T → F (for num(3)): T.val = F.val = 3
• E → T (for num(3)): E.val = T.val = 3
• E → E + T: E.val = E.val (from num(3)) + T.val (from 2 * 4) = 3 + 8 = 11

Therefore, the result of the computation... Continue reading "Compiler Design: SDTS, LR Parsing, and Code Optimization" »

Lecture 1: Moore's Law

Moore's Law: The number of transistors on microchips doubles every two years.

Lecture 2: Logic Gates

AND, OR, and NOT gates are universal.

Logic word problem steps:

Example: In a bank, there were four employees: the bank manager, assistant manager, teller, and the security guard. The bank has a single vault for the storage of their money. This vault was designed so that it needs four signals to open it. These four signals are from the bank manager, assistant manager, teller, and the security guard. For the vault to open, it needs the following conditions:

1. No single employee can open the vault.
2. It can be opened with three employees as long as one of them is the manager.
3. It can be opened by the manager together with the assistant

Q1. Array Address Calculation (Row & Column Major)

Problem: An array ARR[-5...15, 10...20] stores elements in Row Major with each element requiring 2 bytes. Base address is 2500. Find the address of ARR[10][15].

Answer:

• Row range: -5 to 15, so Lr = -5, Ur = 15
• Column range: 10 to 20, so Lc = 10, Uc = 20
• Element size (w) = 2 bytes
• Base Address (BA) = 2500

Step 1: Calculate dimensions

• Number of rows (M) = Ur - Lr + 1 = 15 - (-5) + 1 = 21
• Number of columns (N) = Uc - Lc + 1 = 20 - 10 + 1 = 11

Step 2: Row Major Order Formula

Address(A[i][j]) = BA + [(i - Lr) × N + (j - Lc)] × w
Address(ARR[10][15]) = 2500 + [(10 - (-5)) × 11 + (15 - 10)] × 2
= 2500 + [15 × 11 + 5] × 2
= 2500 + [165 + 5] × 2
= 2500 + 170 × 2 = 2840

Step 3: Column Major Order Formula

Address(... Continue reading "Data Structures and Algorithms Practice Problems" »

Here is a complete and concise answer sheet for your Digital Electronics CIE-1 preparation based on your questions:

1. Design Half and Full Subtractor with Truth Table

Half Subtractor

• Inputs: A, B
• Outputs: Difference (D), Borrow (Bo)
• Logic Equations:
  • Difference (D) = A ⊕ B
  • Borrow (Bo) = A' · B

Full Subtractor

• Inputs: A, B, B_in (Borrow In)
• Outputs: Difference (D), Borrow Out (B_o)
• Logic Equations:
  • D = A ⊕ B ⊕ B_in
  • B_o = B · B_in + B · A' + A' · B_in

2. Working of Adder and Subtractor

Adder Circuits

• Half Adder: Adds two bits A and B.
  • Sum = A ⊕ B, Carry = A · B
• Full Adder: Adds three bits A, B, and C_in.
  • Sum = A ⊕ B ⊕ C_in, C_out = AB + AC_in + BC_in

Subtractor Circuits

• Half Subtractor: Subtracts B from A.
  • Difference = A ⊕ B, Borrow = A' · B
• Full Subtractor:

Logical Volume Management (LVM) in Linux Storage

F. The the vast realm of operating systems, Linux has emerged as a robust and versatile choice, powering everything from personal computers to enterprise-level servers. One of its standout features is Logical Volume Management (LVM), a powerful storage management system that offers enhanced flexibility, scalability, and reliability for handling storage devices in Linux environments. LVM revolutionizes how disk partitions and physical storage are managed, providing an abstract layer that simplifies storage administration and facilitates efficient utilization of available resources. By introducing logical volumes, volume groups, and physical volumes (PVs) (originally referred to as "physical books"... Continue reading "Mastering LVM: Dynamic Storage Management in Linux" »

Domain Model

• Shows concepts only: classes, attributes, associations, and multiplicities.
• No methods, no UI, and no controllers are included.
• Purpose: To understand the real-world objects involved in the system.

Use Case Model (Module 6)

• Focuses on Actor ↔ System interaction.
• Uses the Verb + Noun naming convention.
• Format: Defines Actor steps versus System steps.
• Use cases serve as input for sequence diagrams, which inform class diagrams.

UML Class Diagram (Module 7)

• Class Components: Name, attributes, and methods.
• Association: Line connecting classes with multiplicity (1, 0..1, *, 1..*).
• Inheritance: Represented by an open triangle arrow symbol.
• Interface: Indicated by the «interface» stereotype.
• DCD (Design Class Diagram): Explicitly includes methods

Understanding Objects in Programming

An object is a software entity that contains data (attributes) and methods. It represents a real-world entity that can be distinctly identified.

Every object has a unique:

• Identity: The name of the object (e.g., the variable name).
• State: The data stored in the object, which defines its properties.
• Behavior: The actions an object can perform, defined by its methods.

Can an object be passed as an argument to a function?

Yes. In Python, objects are passed by reference. This means any changes made to the object's attributes within the function will permanently alter the original object. This behavior is similar to how lists and dictionaries are handled. Think of it as sharing a key to a single locker rather than getting... Continue reading "Python Classes, Objects, and Inheritance Fundamentals" »