C: : Types, Values, and Variables (part 1)

Chapter Three: Types, Values, and Variables

General Overview of Types

  • Types refer to the kinds of values that something can take on and the operations that can be performed on these values in programming.

Operations on Different Types

  • Numbers

    • Operations: Add (+), Subtract (-), Multiply (*), Divide (/)

    • Example: If x = 2, then x + 3 = 5

  • Strings

    • Defined as a series of characters.

    • Example: The string "one" and the string "two" can be concatenated using the plus symbol (+) to become "onetwo".

    • Concatenation: The process of joining strings together.

Variables

  • Definition: Variables are named references used to store values for later use in a program.

  • Examples of Variable Assignments:

    • x = 2

    • shoe_cost = 99.99

  • Use Cases for Variables:

    • Storing user input.

    • Assigning constants for later use (e.g., tax rate).

Types of Groupings in JavaScript

  • JavaScript categorizes types into primitive types and object types.

  • Primitive Types:

    • Includes:

    • Numbers

    • Strings

    • Booleans

    • Null

    • Undefined

  • Object Types:

    • Everything that is not a primitive type, allowing for holding multiple values, methods, and attributes.

Memory Management

  • Garbage Collection

    • A mechanism that automatically manages memory allocation and deallocation, freeing memory that is no longer in use.

    • In contrast to older languages, where programmers had to manage memory manually, JavaScript does it automatically.

Working with Numbers in JavaScript

  • Type of Numbers:

    • JavaScript uses a unified number type, which is a 64-bit floating point.

    • This means that both integers and floating points are treated as floating points.

  • Arithmetic Operations Example:

    • 1 + 1 equals 2.

Math Object Functions

  • Functions available in the Math object include:

    • Math.pow(base, exponent) - Raises base to an exponent.

    • Example: Math.pow(2, 53) gives a large number.

    • Math.round(value) - Rounds to nearest integer.

    • Math.ceil(value) - Rounds upwards to nearest integer.

    • Math.floor(value) - Rounds downwards to nearest integer.

    • Math.abs(value) - Gets the absolute value.

    • Common properties: Math.PI, Math.E.

Special Numerical Cases

  • Overflow and Underflow

    • Overflow: Occurs when a variable exceeds its limit, resulting in the value being represented as infinity.

    • Underflow: Occurs when a number becomes too close to zero, which can result in the default value of zero.

  • Division by Zero:

    • In JavaScript, dividing by zero produces Infinity or -Infinity, depending on the sign of the number.

    • Dividing zero by zero results in NaN (Not a Number).

  • NaN Characteristics:

    • NaN is not equal to anything, including itself.

Binary Floating Point Representation

  • Concept: Numbers in computers are represented as binary floating-point numbers, which can lead to precision issues and rounding errors.

  • Rounding Errors: Comparing floating point values directly can lead to unexpected results due to small inaccuracies in representation.

Working with Dates and Times

  • Date Creation: Using the new Date() constructor.

    • Example: var then = new Date(2010, 0, 1); creates a date object for January 1, 2010.

    • Example: var now = new Date(); retrieves the current date and time.

  • Date Methods:

    • getFullYear(), getMonth(), getDate() for retrieving respective date components.

Understanding Strings in JavaScript

  • Strings are defined as immutable sequences of characters.

    • Once a string is created, it cannot be changed; any modification results in a new string.

  • String Properties:

    • Length Property: name.length returns the number of characters in the string.

    • Example: If var name = "Adrian";, then name.length returns 6.

  • String Literals:

    • Can be single or double-quoted (e.g., "Hello World!").

    • Escape Sequences: Used to include special characters in strings.

    • Example: "This is a string with a newline character:\nNext Line!"

Boolean Values

  • Boolean values only return true or false.

    • Example: 5 == 5 evaluates to true, while 5 == 4 evaluates to false.

  • Usage in Conditional Statements:

    • Commonly used in conditionals (e.g., if statements) to control program flow based on logical comparisons.

Conclusion of Lecture

  • This lecture has introduced fundamental concepts surrounding types, values, and variables in JavaScript, providing a foundation for deeper exploration in subsequent lectures.