Programming Language History and Grammar Concepts

Programming Language History

• COBOL: Developed by Grace Hopper, used for businesses and defense.
• ALGOL: First language to have syntax formally defined with Backus-Naur Form (BNF).
• Fortran: Pioneered high-level programming languages.
• LISP/Scheme: Used for artificial intelligence.
• Ada: First widely used language named after Ada Lovelace.
• BASIC: Emphasized user convenience over computer efficiency, easy for non-science students.
• Java: High-level, object-oriented language with classes.
• Python: High-level, known for being easy to learn.

Grammar

• Grammar Components: Consists of terminals, non-terminals, the start symbol, and the result.
• Left Derivation: Derivations are performed one at a time.
• Legal Phrases: Can be found within the defined grammar, while illegal phrases are absent.

Axiomatic Semantics

• Precondition: Found by determining the statements that need to be true in the postcondition to ensure the correctness of the program.

Types of Semantics

• Operational Semantics: Looks at the overall program execution and output.
• Denotational Semantics: Analyzes each line of code to verify compliance with language rules.
• Axiomatic Semantics: Focuses on verifying the truth of postconditions.

Language Constructs

• Syntax: The rules governing the structure of a language.
• Semantics: The meaning of a language's constructs.
• Lexer: A compiler component that identifies lexemes.
• Parser: A compiler component that creates syntax trees from lexemes.
• Compiler: Translates high-level programs into machine code for execution.
• Interpreter: Executes programs directly without translation, enabling immediate error reporting.
• Token: A categorization of lexemes.
• Lexemes: The smallest meaningful units in a language.

Evaluating Languages

• Readability: How easily programs can be understood.
• Writability: How easily programs can be written.
• Reliability: Conformance to specifications and desired behavior.
• Cost: The total cost of using and maintaining a language.

Variable Attributes

• Type: The data type a variable holds.
• Value: The data stored in a variable.
• Address: The memory location where a variable is stored.
• Scope: The region of code where a variable is accessible.
• Lifetime: The duration during which a variable exists in memory.
• Name: The identifier used to reference a variable.

Types of Scope

• Static Scope: The scope of a variable is determined by its position within the program structure.
• Dynamic Scope: The scope of a variable is determined by the calling sequence of subprograms.

Primitive Data Types

• Int: Integer numbers.
• Char: Single characters.
• Boolean: True or False values.
• Float: Single-precision floating-point numbers.
• Double: Double-precision floating-point numbers.
• String: Sequences of characters.

Memory Problems

• Dangling Pointers: Pointers that point to memory locations that no longer hold valid data.
• Garbage: Unreachable memory blocks that are no longer in use.

Garbage Collection Techniques

• Mark-Sweep: Reclaims unused memory cells only when available space becomes low.
• Reference Counting: Reclaims cells when they stop being referenced.

Range Types

• Ordinal: Ranges of values that can be mapped to integers.
• Enumeration: Explicitly specifies all possible values.
• Subrange: A contiguous subsequence of an ordinal type.

Referencing Environment

• Referencing Environment: The set of names that are visible within a particular statement.

Ancestor Relationships

• Static Ancestor: The parent program and its parent programs up to the main program (including the program itself).
• Dynamic Ancestor: The calling function and its calling functions up to the initially invoked program.

Binding Times

• Load Time: Binding happens when the program is loaded into memory for execution.
• Compile Time: Binding happens during the compilation process.
• Run Time: Binding happens during the execution of the program.
• Link Time: Binding occurs when different program modules are combined into a single executable file.

Stack vs. Heap

• Stack: A memory region that uses a Last-In-First-Out (LIFO) strategy to allocate memory for local variables and function calls. It's faster but has limited capacity.
• Heap: A memory region that allows dynamic memory allocation for data with longer lifespans. It offers flexibility but requires manual management and is slower than the stack.

Object-Oriented Programming (OOP)

• Key Principles: Abstraction, Inheritance, Polymorphism.
• Abstract Data Types: Defines the structure and behavior of objects.
• Inheritance: Allows classes to inherit properties and methods from other classes (superclasses).
• Polymorphism: Enables objects to behave differently based on their type, allowing for diverse and flexible object interactions.

OOP Concepts

• Object: An instance of a class.
• Derived Class: A class that inherits from another class (subclass).
• Superclass: The class from which another class inherits (parent class).
• Method: A subprogram that defines an operation on an object.
• Message: A call to a method.
• Dynamic Binding: Determines the specific method to be called at runtime based on the object's type.
• Polymorphic Variable: A variable that can reference objects of a class and any of its descendants.
• Abstract Method: A method that is declared but not defined, providing an interface for derived classes to implement.

Inheritance Types

• Single Inheritance: A class inherits from a single parent class.
• Multiple Inheritance: A class can inherit from more than one parent class.

Explore the evolution of programming languages from COBOL to Python and the foundational grammar components that define them. This quiz also delves into axiomatic semantics, examining preconditions and legal phrases. Test your knowledge on the critical elements of programming languages and their grammar!