ECE115

Computing refers to performing systematic logical and arithmetic operations to process, store, and retrieve data.

Decimal is historically rooted in human anatomy, as humans typically have ten fingers.

Binary uses only two states—0 and 1—corresponding to OFF/ON or LOW/HIGH voltage levels, making hardware simpler, reliable, and efficient.

It referred to humans, often women, who performed complex mathematical calculations manually.

Babbage aimed to reduce errors in manual calculations and automate mathematical computations to save time and improve reliability.

Electrical systems enable faster, more reliable, and scalable computations compared to mechanical systems.

The transistor (1947), which replaced vacuum tubes, and the integrated circuit (1958), which combined multiple transistors into a chip.

Transistors are smaller, consume less power, and are more reliable than vacuum tubes.

Technological advancements, user expectations for faster devices, and innovations in software require increasingly powerful systems.

There is no definitive endpoint for computational requirements. As technology evolves, new challenges emerge that demand more powerful computing systems. Examples include quantum computing for cryptography and AI for healthcare.

A programmable electronic device that processes data by executing instructions and consists of hardware and software.

Keyboard and Mouse.

Monitor and Printer.

CPU stands for Central Processing Unit. It executes instructions, processes data, and manages tasks in the computer system.

Memory is needed to temporarily store data and instructions for quick access by the CPU, ensuring efficiency during computations.

ALU stands for Arithmetic Logic Unit. Arithmetic refers to mathematical operations, and Logic refers to comparison operations.

Clock Speed and Number of Cores.

ISA stands for Instruction Set Architecture. It defines the set of commands a CPU can execute, forming the interface between hardware and software.

RAM provides temporary, fast storage for running applications, while SSD provides long-term, non-volatile storage for data and applications.

Memory hierarchy organizes storage devices based on speed, cost, and capacity. It improves performance by storing frequently accessed data in faster layers. Analogy: Your desk (RAM) holds immediate-use items, while filing cabinets (SSD) store less frequently used documents.

With n bits, you can encode
2
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2
n
different things.

A program is a set of instructions written in a specific programming language to perform a task.

Software refers to programs and operating systems that control hardware and allow users to perform tasks.

An operating system (OS) is the software that manages hardware resources and provides an interface for user interactions.

Resource Management and User Interaction.

Standard input refers to the keyboard; standard output refers to the monitor.

GUI stands for Graphical User Interface. It allows users to interact with computers using visual elements like windows and buttons.

CLI stands for Command Line Interface. It allows users to interact by typing text-based commands into a terminal.

The drone hovers when the upward thrust equals the gravitational pull acting on it.

Propellers generate lift to overcome gravity and control the drone's movement.

By increasing the speed of all propellers to generate more thrust than gravity.

By varying the speed of specific propellers to tilt the drone in the desired direction.

By gradually reducing the propeller speed so that thrust becomes less than gravity.

Opposite rotational directions counteract torque effects, preventing the drone from spinning uncontrollably.

Abstraction hides complex details, allowing users to focus on high-level functionality, such as controlling a drone with simple commands.

Programming is creating a set of instructions that a computer can execute to perform specific tasks.

They simplify instructions for humans and reduce errors compared to writing machine code.

Binary instructions directly executed by the CPU.

High-level languages are human-readable and portable; low-level languages are closer to machine code and hardware-dependent.

High-level languages are portable and human-readable.

A compiler translates the entire code before execution, making it faster; an interpreter translates and executes line-by-line, making it interactive.

"Write Once, Run Anywhere" enables Java programs to run on any platform with a JVM.

The rise of the internet and the need for platform-independent web applications.

Universality: Ability to simulate any computation. Syntax: Rules for writing code. Semantics: Meaning of instructions.

Java uses bytecode and the JVM to achieve platform independence.

The Java compiler is called javac.

Bytecode is intermediate code generated by the compiler, executed by the JVM.

JVM stands for Java Virtual Machine, which executes Java bytecode.

IDE stands for Integrated Development Environment, which simplifies development with tools like debugging and code generation.

A collection of related classes organized for reusability and to prevent naming conflicts.

The java.lang package.

It imports the ArrayList class from the java.util package.

It imports all classes from the java.util package.

To improve readability and document the code.

An algorithm is a set of well-defined instructions or steps designed to solve a specific problem or perform a task.

Sequencing, Selection, and Repetition.

Sequencing is the execution of instructions in the order they appear, like adding two numbers and displaying the result.

Selection involves decision-making based on conditions, such as using an if-else statement to check whether a number is even or odd.

Repetition is executing a block of code multiple times, such as using a for loop to print numbers from 1 to 5.

Variables act as containers for storing data values that may change during program execution. For example: int age = 25; assigns the value 25 to the variable age. Local variables are not initialized automatically and must be explicitly assigned values.

Constants store values that do not change during program execution. Declared using the final keyword. For example: final double PI = 3.14159; assigns a constant value of 3.14159 to PI.

Instance variables have default values: int: 0, double: 0.0, char: 0000, boolean: false, and reference types: null.

Variables allow for reusability, avoiding hardcoding values multiple times. They also enable efficient memory management by allocating specific storage for data.

Memory is allocated based on the data type. For example, declaring int i = 20; allocates 4 bytes of memory and stores 20 in binary: 00000000 00000000 00000000 00010100.

A data type defines the kind of data a variable can store and the operations allowed on that data.

1. Primitive Types: Built-in types like int, double, char, boolean. For example: int number = 10;, double price = 19.99;. 2. Reference Types: Types created by the programmer or provided by Java, such as String, Array, Object.

int: 4 bytes, double: 8 bytes, char: 2 bytes, boolean: 1 byte, short: 2 bytes, long: 8 bytes.

No, 5 is an int (integer) while 5.0 is a double (floating-point number).

Declaration: int score;. Assignment: score = 100;. Combined: int score = 100;.

The output is 2. % (modulus) has higher precedence than + or *. Evaluate 3 * 4 % 3 → 12 % 3 = 0, then 1 + 0 = 2.

i++: Assigns i to j, then increments i. For example: int i = 5; int j = i++; // j = 5, i = 6. ++i: Increments i first, then assigns to j. For example: int i = 5; int j = ++i; // j = 6, i = 6.

Shorthand operators combine assignment with operations. For example: int x = 5; x += 3; // Equivalent to x = x + 3;.

NaN stands for "Not a Number," representing undefined operations, like 0.0 / 0.0.

Infinity results from division by zero, such as 1.0 / 0.0.

ASCII assigns numerical codes to characters, providing consistent encoding for text. Java uses Unicode, which includes ASCII and supports more global characters.

Images are stored as binary data, not human-readable text. A text reader misinterprets binary data as characters, resulting in gibberish.

Escape sequences are special character combinations beginning with \. For example, \n creates a new line in the output.

The \n escape sequence inserts a new line in the output. For example: System.out.println("Hello\nWorld");. Output: Hello (newline) World.

Type: int. Value: 1 (ASCII value of 'b' is 98, 'a' is 97, so 98 - 97 = 1).

1. OR (|): Combines bits. 6 | 8 = 14 // Binary: 0110 | 1000 = 1110. 2. AND (&): Extracts common bits. 6 & 8 = 0 // Binary: 0110 & 1000 = 0000. 3. XOR (^): Identifies differing bits. 6 ^ 8 = 14 // Binary: 0110 ^ 1000 = 1110.

Conditionals allow programs to make decisions based on specific conditions, enabling different execution paths.

The if statement executes a block of code if the condition evaluates to true. Example:
if (x > 0) { System.out.println("x is positive"); }

The if-else statement executes one block if the condition is true and another block if it is false. Example:
if (x > 0) { System.out.println("x is positive"); } else { System.out.println("x is not positive"); }

The if-else if ladder evaluates multiple conditions in sequence. Example:
if (x > 0) { System.out.println("x is positive"); } else if (x == 0) { System.out.println("x is zero"); } else { System.out.println("x is negative"); }

Nested if-else statements allow one conditional block to contain another. Example:
if (x > 0) { if (x % 2 == 0) { System.out.println("x is positive and even"); } else { System.out.println("x is positive and odd"); } }

The ternary operator is a shorthand for if-else statements. Syntax: condition ? value_if_true : value_if_false. Example:
String result = (x > 0) ? "positive" : "not positive";

The switch statement evaluates an expression and executes the matching case block. Example:
switch (day) { case 1: System.out.println("Monday"); break; case 2: System.out.println("Tuesday"); break; default: System.out.println("Invalid day"); }

Compound boolean expressions combine conditions using logical operators like &&, ||, and !. Example:
if (x > 0 && y > 0) { System.out.println("Both x and y are positive"); }

Use .equals() instead of == for comparing strings. Example:
String a = "Hello"; String b = "Hello"; if (a.equals(b)) { System.out.println("Strings are equal"); }

Loops allow repetitive execution of a block of code until a specified condition is met.

The while loop repeats code as long as the condition is true. Example:
int i = 0; while (i < 5) { System.out.println(i); i++; }

The do-while loop executes the code block at least once before checking the condition. Example:
int i = 0; do { System.out.println(i); i++; } while (i < 5);

The for loop is used to iterate a specific number of times. Example:
for (int i = 0; i < 5; i++) { System.out.println(i); }

The enhanced for loop iterates over elements in an array or collection. Example:
int[] numbers = {1, 2, 3}; for (int num : numbers) { System.out.println(num); }

Nested loops are loops inside another loop. Example:
for (int i = 0; i < 3; i++) { for (int j = 0; j < 2; j++) { System.out.println("i = " + i + ", j = " + j); } }

The break statement exits the loop prematurely. Example:
for (int i = 0; i < 10; i++) { if (i == 5) { break; } System.out.println(i); }

The continue statement skips the current iteration and moves to the next. Example:
for (int i = 0; i < 5; i++) { if (i == 2) { continue; } System.out.println(i); }

Example:
int[] numbers = {10, 20, 30}; int max = numbers[0], min = numbers[0], sum = 0; for (int num : numbers) { if (num > max) max = num; if (num < min) min = num; sum += num; } double avg = (double) sum / numbers.length;

Example:
int num = 12345, reversed = 0; while (num != 0) { int digit = num % 10; reversed = reversed * 10 + digit; num /= 10; } System.out.println("Reversed: " + reversed);

An array is a data structure that stores multiple elements of the same data type in contiguous memory locations.

int: 0, double: 0.0, boolean: false, String or objects: null.

Declaration: int[] numbers;. Creation: numbers = new int[5];. Combined: int[] numbers = new int[5];.

Syntax: int[] numbers = {1, 2, 3};.

Access: int firstElement = numbers[0];. Modify: numbers[0] = 10;.

int[][] matrix = new int[3][3];.

A shallow copy copies the reference to the original array, not the elements. Example: int[] copy = original;.

A deep copy creates a new array and copies the elements. Example:
int[] copy = new int[original.length]; for (int i = 0; i < original.length; i++) { copy[i] = original[i]; }.

ArrayIndexOutOfBoundsException occurs when accessing indices out of range. NullPointerException occurs when accessing an uninitialized array.

Sort: Arrays.sort(numbers);. Search: int index = Arrays.binarySearch(numbers, 3);.

A static method belongs to the class and can be called without creating an object. Example: Math.sqrt(4);.

Static methods are used for class-level operations, reusability, and memory efficiency.

public static returnType methodName(parameters) { // Code block }. Example: public static int square(int num) { return num * num; }.

The main method is the entry point of Java applications. Syntax: public static void main(String[] args) { // Code }.

A method with void does not return a value. Example: public static void greet() { System.out.println("Hello!"); }.

Function overloading allows methods with the same name but different parameter lists. Example: int multiply(int a, int b); double multiply(double a, double b);.

Local variables are accessible only within the method they are declared in. Example: public static void example() { int localVar = 10; }.

For primitive types, only the value is passed, and changes do not affect the original variable. Example: modifyValue(original); // original remains unchanged.

A copy of the reference is passed; changes to the object affect the original. Example: modifyArray(numbers); // Changes numbers[0].

Recursion is when a method calls itself to solve smaller instances of a problem. Example: public static int factorial(int n) { if (n == 1) return 1; return n * factorial(n - 1); }.

The practice of securing information through encryption to prevent unauthorized access.

An encryption algorithm that shifts each letter in the plaintext by a fixed number of positions in the alphabet. Example: HELLO shifted by 3 becomes KHOOR.

Reducing the size of data to save space or improve transmission speed.

Lossless Compression (no data lost, e.g., ZIP files) and Lossy Compression (some data lost, e.g., MP3, JPEG).

Encoding repeated characters as a single character and count. Example: Input: AAAABBBCCDAA, Output: 4A3B2C1D2A.

Manipulating images to improve quality or extract information.

The smallest unit of an image, representing its color.

30,000 bytes (30 KB). Formula: width × height × color depth / 8.

Manipulating audio signals to improve quality or extract features.

Sampling converts continuous audio into discrete values at intervals, while quantization assigns numeric values to the sampled data.

To save storage space, reduce bandwidth usage, and make large files more manageable.

Computers use binary because it aligns with their electrical states (1 = ON, 0 = OFF).

Computers use binary because it aligns with their electrical states (1 = ON, 0 = OFF).

A bit is the smallest unit of data, representing 0 or 1. A byte consists of 8 bits and can represent values from 0 to 255.

An unsigned integer represents non-negative numbers. Range for n bits: 0 to 2n−12^n - 12n−1.

The range is 0 to 15.

A signed integer can represent both positive and negative numbers. Common representations include Sign-Magnitude and Two's Complement.

The MSB represents the sign (0 = positive, 1 = negative), and the remaining bits represent the magnitude. Example: +5+5+5 in 4 bits = 0101, −5-5−5 = 1101.

Two's Complement represents negative numbers by inverting the bits of the absolute value and adding 1. Example: +5+5+5 = 0101, −5-5−5 = 1011.

The range is −8-8−8 to 777.

The IEEE 754 standard defines the representation of floating-point numbers with Sign, Exponent, and Mantissa.

Sign = 1, Exponent = 130, Mantissa = Binary equivalent of 5.755.755.75.

Single precision: 32 bits. Double precision: 64 bits.

Two's Complement simplifies arithmetic and provides a unique representation for zero.

Overflow occurs when the result exceeds the range of the representation. Example: 4-bit unsigned 15+1=015 + 1 = 015+1=0, signed 7+1=−87 + 1 = -87+1=−8.

A Deterministic Finite Automaton is a theoretical machine used to recognize patterns in input strings.

States, Alphabet, Transitions, Start State, Accept State(s).

The initial state where the DFA begins processing input.

The state where the DFA accepts the input string.

Use four states: q0 (start), q1, q2, and q3 (accept). Transitions: q0 -> q1 on 1, q1 -> q2 on 0, q2 -> q3 on 0.