The historical development of programming languages has gone through one stage after another, from machine language to high-level language, it is also closer to the way of human thinking, easy to write, good readability, and more efficient to develop.

  • Machine-oriented programming (MOP)
  • Procedure-oriented Programming (POP)
  • Object-oriented Programming (OOP)
  • …

Programming itself is engineering, not science. This means that all roads lead to Rome, and there is no one size fits all. So, in fact, many people argue about them by different aspects (e.g. coding style, performance, the difficulty of mastering), which language is the best, which framework is better, these are actually philosophical questions, because there is no unified standard answer.

Difficulty of Mastering

Different programming languages have some similarities in common, but also have their own uniqueness, they are all born to solve certain problems, no one language is absolutely good, and they all have their own philosophical ideas.

Languages:

  • Ruby: Optimized for programmer happiness
  • Python: Beautiful is better than ugly
  • PHP: Quick and dirty
  • Java: Compile once, run everywhere
  • …

Categories

Dynamically Typed Language

A language that checks the type of data at runtime. Such languages do not assign a type to a variable, but get the data type when a value is assigned.

Languages:

  • ECMAScript (JavaScript)
  • Python
  • Ruby
  • PHP
  • Erlang
  • VBScript
  • Swift
  • Perl
  • …

Statically Typed Language

Statically typed languages check the type at compile time before running. When writing code, each variable declared must specify the type.

Languages:

  • C/C++
  • C#
  • Object-C
  • Java
  • Scala
  • Go
  • …

PS. Whether a language is dynamically typed or not is completely irrelevant to whether the language is typesafe, don’t tie them together.

Dynamic Programing Language

Dynamic languages (Dynamic Programming Languages) are a class of languages that can change their structure at runtime.

Languages:

  • C#
  • Object-C
  • Python
  • PHP
  • Erlang
  • JavaScript
  • …

Static Programing Language

Static languages (Static Programming Languages) are languages whose structure cannot be changed at runtime.

Languages:

  • C/C++
  • Java
  • …

Strongly Typed Language

Strongly typed means that the type of a value doesn’t change in unexpected ways. A string containing only digits doesn’t magically become a number, as may happen in Perl. Every change of type requires an explicit conversion.

E.g. 1 / 3 = 0, int / int = int

Languages:

  • C/C++
  • C#
  • Object-C
  • Java
  • Python
  • Ruby
  • Go
  • …

Weakly (Loosely) Typed Language

Weakly typed languages are looser in checking variable types and tolerate implicit type conversions.

E.g.

  • 1 / 3 = 0.33333..., int / int = float
  • 1 + "3" = 13, int / string = string

Languages:

  • JavaScript
    • Duck Typing (i.e. looks like a duck, talks like a duck, it’s a duck)
  • PHP
  • …

Compiled Language

Compiled language means that a special compilation process is required before the program is executed, and the program source file is compiled into a file in machine language, which can be executed by the machine and has high execution efficiency.

Languages:

  • C/C++
  • Object-C
  • Pascal
  • Swift
  • …

Interpreted Language

Interpreted language means that the source code does not need to be compiled in advance, at runtime, it must be interpreted before running.

Languages:

  • JavaScript
  • Python
  • PHP
  • Perl
  • Ruby
  • Erlang
  • Java
  • C#
  • …

For Java and C#, it can be said to be a semi-compiled and semi-interpreted language. The source code needs to be converted into an intermediate file (bytecode file), and then the intermediate file is taken to the virtual machine for execution.

Programming Paradigms

Paradigms Relationship

Imperative Programming

This alternative to OOP focuses on function rather than models.

Languages:

  • C++
  • Java
  • …

Declarative Programming

This programming method involves statements on what the task or desired outcome is but not how to achieve it.

Languages:

  • Prolog
  • Lisp
  • …

Logical Programming

This programming method, which is based mostly in formal logic. It contains a set of sentences that express facts or rules about a problem domain. It focuses on tasks that can benefit from rule-based logical queries.

Languages:

  • Prolog
  • …

Functional Programming (FP)

FP is a high level way of programming, the level stands for the degree of abstraction, the higher the programming level is, the least the concern of machine execution details is, such as memory allocation and release, all low level stuff just let the compiler to handle. And it is very worthwhile to exchange a little performance for a clean program.

Behavior: Use imperative rather than declarative

  • Imperative
    • Focus on the steps of execution (machine-oriented)
    • Examples
      • Assembly Language
  • Declarative
    • Focus on the expression of execution (human-oriented)
      • numbers.filter(num => num % 2)
      • SELECT name, age from Students
    • Examples
      • SQL

Basic Concept:

  • Pure Functions
    • It’s actually a kind of functions
    • But it must meet certain restrictions
      • The same input always result the same output
      • No side effects (i.e. Closure)
      • How to handle the side effects
        • It’s to use monad to push the impure part to the boundary of the program, and keep the core part pure
    • Try to make all functions pure as much as possible
    • Advantages
      • Its result is predictable
      • Make unit test very easy, as no any external dependency
  • State Immutability
    • All variables can’t be changed once they are declared.
  • Avoid Loops
    • Recursion > Loops
    • Using recursion rather than explicit looping structure
    • The nature of the loop is actually very mutable

Languages:

  • Haskell
  • Erlang
  • Scala
  • …

Structured or Modular Programming

The structured is any programming when functionality is divided into units like for loop, while loop, if… then etc block structure. The modular is one can create a physical form of package, which are fairly general purpose and re-usable. So one can hardly see modular programs which are not structured and vice versa; the technical definition is subtly different but mostly structured code can be made modular and other way.

Languages:

  • C#
  • PHP
  • …

Imperative Programming

This alternative to OOP focuses on function rather than models.

Languages:

  • C++
  • Java
  • …

Declarative Programming

This programming method involves statements on what the task or desired outcome is but not how to achieve it.

Languages:

  • Prolog
  • Lisp
  • …

Logical Programming

This programming method, which is based mostly in formal logic. It contains a set of sentences that express facts or rules about a problem domain. It focuses on tasks that can benefit from rule-based logical queries.

Languages:

  • Prolog
  • …

Object-oriented Programming (OOP)

OOP is a form of structured programming by definition.

Abstraction:

  • Encapsulation
  • Inheritance
    • Override (Type and quantity of parameters are the same)
    • Overload (Anyone of type and quantity of parameters is different)
  • Polymorphism

Accessibility (Access modifier):

  • Public
    • Access by any class
  • Protected
    • Access by subclass
  • Friendly
    • Access by friend’s class (e.g. the same package)
  • Private
    • Access by the class itself

Lifecycle:

  • Construction

  • Destruction

  • Instance function
  • Class function (i.e. Also known as Static Function in POP)

Programming Model

In programming, the way of abstraction, organization or reuse of code. The programming model is mainly methods and ideas.

  • Event-driven (Publish/Subscribe Model)
    • Basic
      • Don’t care about who is the receiver
    • Components
      • Event Queue
      • Event Mediator
      • Event Channel
      • Event Processor
    • Frameworks
      • select
      • poll
      • epoll
      • libev
      • interrupt system
  • Message-driven
    • Basic
      • Care about who is the receiver
    • Framework
      • API Gateway
      • gRPC
      • Micro-service Architect
  • Data-driven

Basic

Automatic Checking

It’s useful to think about three kinds of automatic checking that a language can provide:

  • Static checking: the bug is found automatically before the program even runs.
  • Dynamic checking: the bug is found automatically when the code is executed.
  • No checking: the language doesn’t help you find the error at all. You have to watch for it yourself, or end up with wrong answers.

Needless to say, catching a bug statically is better than catching it dynamically, and catching it dynamically is better than not catching it at all.

Preprocessors

Comment

  • Single-line comment
  • Multi-line comment
  • Documentation comment (Docstring)

Data Types

According to the classification:

  • Basic
    • Number
      • Byte (1 Byte = 8 Bits)
      • Short (2 Bytes = 16 Bits)
      • Integer (4 Bytes = 32 Bits)
      • Long (8 Bytes = 64 Bits)
      • Float (4 Bytes = 32 Bits)
      • Double (8 Bytes = 64 Bits)
    • Character (1 Byte = 8 Bits)
    • Boolean
  • Arrays and Collection
    • Linear
      • Array
      • String
      • List
      • Linked list
      • Tuple
      • Queue
      • Stack
    • Non-linear
      • Set
      • Map

According to the structure:

  • Primitive Types
  • Object Types

Keywords and Identifier

  • Case Sensitive
  • Case Insensitive

Value Notation

  • Definition
    • Literal
    • Constant
    • Variable
  • Lifecycle
    • Static
    • Dynamic
  • Value
    • Mutating values
      • Final
      • Readonly
    • Reassigning variables

Examples:

  • null
  • undefined
  • NaN (Not a Number)
  • POSITIVE_INFINITY
  • NEGATIVE_INFINITY
  • 123
  • 1.23
  • true
  • false
  • 123f
  • ‘1’
  • “123”
  • …

Operators

  • Arithmetic Operators
    • +, -, *, /, %, ++, --, …
  • Relational Operators
    • ==, !=, >, <, >=, <=, ..
  • Logical Operators
    • &&, ||, !, …
  • Bitwise Operators
    • AND &
    • OR |
    • XOR ^
    • FLIPPING ~
    • LEFT SHIFT <<
    • RIGHT SHIFT >>
    • …
  • Assignment Operators
    • =, +=, -=, *=, /=, %=, <<=, >>=, &=, |=, |=, …
  • Misc Operators
    • sizeof()
    • Conditional Expression Condition ? Exp1 : Exp2
    • Address Operator &variable
    • Pointer Operator *variable

Basic Structures

In structured programming, a program is written with only 3 basic structures:

  • Sequences
  • Selections
    • if statement
    • switch statement
  • Loops
    • for loop
    • while loop

Functions

  • Variadic function
  • Default value
  • Keyword arguments

Advanced

Iterator

Generator

Decorator

Exception Handle

Lambda

Closure

Asynchronous Programming

  • .NET: delegate
  • Java:
    • Anonymous inner class
    • Closure (Java 7)
  • C++
    • tr1::function/bind (C++0X)
  • …

Destructuring Assignment

Generics Programming

Garbage Collection (GC)

Higher-order Function (HOF)

Dynamic Type conversion

Meta Programming

  • Introspection
    • JAVA: Reflection

Serialization & Deserialization

Hash Value Omission

Language Characteristics

  • Ruby
    • Block
    • Range
    • Symbols
  • Java
    • Dynamic Proxy
  • C#
    • LINQ
    • Extension Method

How to choose a language?

  • Whether the developer is familiar with a language.
  • Which language provides more powerful features that can be applied to the current project.
  • Focus on robustness or flexibility and expressiveness.
  • Whether there are tools to improve development efficiency, such as peripheral frameworks (libraries), etc.
  • …

References