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

Lecture 2: Dynamic Dispatch and Interfaces

• Dynamic Dispatch: The process of selecting which implementation of a polymorphic operation to call at runtime.
• Interface: Calling a method that is not in the interface will cause a compilation error.

Lecture 3: N/A

Lecture 4: Method Contracts, Exceptions, and Unit Testing

• Method Contract: Should define pre/post conditions and exceptional behavior. The client is to blame if the precondition is not met, and the service is to blame if the postcondition is not met. Exceptional behavior specifies what the code will do if a precondition is violated.
• Exception: Runtime exception (unchecked) and IO exception (checked). The IO exception must be caught; otherwise, the code won't compile.
• Unit Test: Test boundary

C++ Priority Queue Implementation

This document provides a C++ implementation of a priority queue using a heap data structure. The code includes the class definition, member functions, and supporting utilities.

Priority Queue Class Definition

#ifndef priority_queue_h_
#define priority_queue_h_

#include <iostream>
#include <vector>
#include <cassert>

template <class T>
class priority_queue {
private:
    std::vector<T> m_heap;

public:
    priority_queue() {}

    priority_queue(std::vector<T> const& values)
    {
        m_heap = values;
        for (int i = 0; i < m_heap.size(); i++){
            percolate_down(i);
            for (int j = i; j < m_heap.size(); j++){
                percolate_down(

This document provides practical SQL Data Definition Language (DDL) examples for creating and modifying database schemas across various common applications. Each section details the necessary tables and their relationships, offering a clear foundation for building robust relational databases.

Library Management System Database

The following SQL DDL statements define the core tables for a library management system, enabling the tracking of books, members, and loan transactions.

Table Creation

CREATE TABLE Books (
    BookID INT PRIMARY KEY,
    Title VARCHAR(100) NOT NULL,
    Author VARCHAR(100) NOT NULL,
    ISBN VARCHAR(20) UNIQUE,
    PublishedYear INT CHECK (PublishedYear >= 1500 AND PublishedYear <= 2025)
);

CREATE TABLE Members (

Compile and Go Loaders

In this type of loader, the linker and loader instructions are read line by line, their machine code is obtained, and it is directly placed in the main memory at some known address. This means the assembler runs in one part of memory, and the assembled machine instructions and data are directly put into their assigned memory locations. After completion of the assembly process, the loader contains the instruction using which the location counter is set to the start of the newly assembled program. A typical example is WATFOR-77, a FORTRAN compiler which uses such a "load-and-go" scheme. This loading scheme is also called "assemble-and-go".

Advantages

• Simplicity
• Quick Testing
• No Separate Linking
• Immediate Feedback
• Low Resource

What is an Exception?

Answer: An exception in Python is an error that occurs during program execution, disrupting the normal flow of instructions. Instead of crashing, the program can "catch" the exception and handle it gracefully using try and except blocks. Common exceptions include ZeroDivisionError, IndexError, and FileNotFoundError. You can also define custom exceptions. The finally block can be used for cleanup actions, ensuring certain code runs regardless of whether an exception was raised.

Different Modes of Opening a File

Answer: Different Modes of Opening a File

1. Read Mode ('r')

• Purpose: Opens a file for reading.
• Behavior:
  • The file pointer is placed at the beginning of the file.
  • If the file does not exist, a FileNotFoundError is raised.

Master-Slave Flip-Flop Operation

The working of a Master-Slave flip-flop involves two cascaded flip-flops: a master and a slave. The master is positive level-triggered, and the slave is negative level-triggered, ensuring the master responds before the slave.

When the clock pulse (CP) goes high (1), the slave is isolated, allowing the J and K inputs to affect the master's state. The slave flip-flop remains isolated until the CP goes low (0). When the CP transitions back to low, information is passed from the master flip-flop to the slave, and the output is obtained.

Let's examine the behavior based on J and K inputs:

• J=0, K=1: The high Q' output of the master goes to the K input of the slave. The negative transition of the clock forces the slave

C Programming Examples

Here are several C programming examples:

Vector Operations

#include <stdio.h>

void leVetor (int v [] , int tam );
int prodEscalar (int v1 [] , int v2 [] , int tam );

int main (void) {
    int v1 [ DIM ], int v2 [ DIM ];
    int i;
    int prod ;

    leVetor (v1 , DIM );
    leVetor (v2 , DIM );
    prod = prodEscalar (v1 , v2 , DIM );
    printf ("%d\n", prod );
    return 0;
}

void leVetor (int v [] , int tam ) {
    /* Completar */
}

int prodEscalar (int v1 [] , int v2 [] , int tam ) {
    /* Completar */
}

Random Number Generation

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

#define VEZES 10

int main (void) {
    int i , j , k;
    double r;

    srand ( time ( NULL )); /* inicializa

Button Click Action Events

import java.awt.*;

import java.awt.event.*;

public class ButtonClickActionEvents

{

public static void main(String args[])

{

Frame f=new Frame("Button Event");

Label l=new Label("DETAILS OF PARENTS");

l.setFont(new Font("Calibri",Font.BOLD, 16));

Label nl=new Label();

Label dl=new Label();

Label al=new Label();

l.setBounds(20,20,500,50);

nl.setBounds(20,110,500,30);

dl.setBounds(20,150,500,30);

al.setBounds(20,190,500,30);

Button mb=new Button("Mother");

mb.setBounds(20,70,50,30);

mb.addActionListener(new ActionListener()

{

public void actionPerformed(ActionEvent e)

{

nl.setText("NAME: " + "Aishwarya");

dl.setText("DESIGNATION: " + "Professor");

al.setText("AGE: " + "42");

}

});

Button fb=new Button("Father");

fb.setBounds(80,70,50,30);

fb.addActionListener(