Javascript history

In the past decades, a large number of programming languages have been invented, replaced, modified or combined. Although people have tried many times to create a universal programming language, none of them succeeded. There are so many different programming languages because the original intention of writing programs is actually different; There is a big technical gap between novices and veterans, and many languages are too difficult for novices to learn. In addition, the runtime costs vary from program to program.

There are many special-purpose languages, which are only used in special occasions. For example, PHP is dedicated to displaying web pages; Perl is more suitable for text processing; C language is widely used in the development of operating systems and compilers (so-called system programming).

Programming languages make computer programs no longer overly dependent on specific machines or environments. This is because programming languages will be compiled into different machine languages on different platforms instead of being directly executed by machines. FORTRAN, one of the earliest programming languages, aims to achieve platform independence.

Although most languages can be compiled and interpreted, most languages work well in only one case. In some programming systems, the program must go through several compilation stages. Generally speaking, the later stage of compilation is often closer to machine language. This common technique was first used in BCPL in the late 1960s. The compiler first compiles a demo program named "Code 0", and then uses a virtualizer to convert it into real code that can run on the machine. This successful technology was later used in Pascal and P codes, as well as Smalltalk and binary codes, although in many cases, intermediate codes are often interpreted rather than compiled.

If the translation mechanism used is to translate the program code to be translated as a whole and then run the internal format, then the translation process is called compilation. Therefore, a compiler is a compiler that takes human-readable program text (called source code) as input data and then outputs executable files (object code). The output executable file can be machine language, directly run by the central processing unit of the computer, or it can be the binary code of some simulators.

If the program code is translated immediately at runtime, then this translation mechanism is called interpretation. Interpreters are usually slower than compilers, but they are usually more flexible because they can interact with the execution environment. See Interpretation Language.

Table of Contents [Show Hide]

Characteristics of 1

1. 1 data and data structure

1.2 instruction and process control

1.3 reference mechanism and reuse

2 History of programming languages

Three Common Programming Languages

[edit] feature

Every programming language can be regarded as a set of formal specifications including grammar, vocabulary and meaning.

These specifications usually include:

Data and data structure

Command and process control

Reference mechanism and reuse

design principle

Most widely used or persistent languages have organizations responsible for standardization, and often meet to create and publish formal definitions of languages and discuss extending or implementing existing definitions.

[Edit] Data and data structure

The data in modern computers are only stored in binary mode, that is, switch mode. In the real world, all kinds of data representing information, such as names, bank account numbers, measured values and the same low-end binary data, are arranged by programming languages and become high-end concepts.

A system that processes data in a program is called a type system); Programming language. The research and design of type system is called type theory. Languages can be divided into static type systems, such as C++ and Java, and dynamic type systems, such as Lisp, JavaScript, Tcl and Prolog. The former can be further divided into languages containing manifest type, that is, the type of each variable and function is explicitly declared, or it is a type inference language (such as mumps, ML).

Most languages can also combine complex data structure patterns (using arrays, lists, stacks, files, etc.). ) Based on the built-in mode. Object-oriented languages (also translated into object-oriented languages) allow programmers to define new data types, namely "objects" or "objects", as well as functions and methods running on objects.

In addition to when and how to determine the relationship between expressions and types, another important issue is which types are defined by the language and which types are allowed as the values of expressions. Low-end languages, such as C programming language, allow programs to name memory locations, memory regions and constants at compile time; ANSI C even allows expressions to return structural values. Functional languages usually allow variables to directly use the value calculated at runtime, rather than indicating the memory address where the value may be stored.

[Edit] Description and Process Control

Once the data is determined, the machine must be told how to deal with it. Simple instructions can be completed using keywords or defined grammatical structures. Different languages use sequential systems to acquire or combine these sentences. In addition, other instructions in the language can also be used to control processing (such as branching, looping, etc.). ).

[Edit] Reference Mechanism and Reuse

The central idea of quotation is that there must be an indirect way to design storage space. The most common method is to name variables. Depending on the language, further references may include pointers to other storage spaces. A similar approach is to name a set of instructions. Most programming languages use macro calls, procedure calls or function calls. Using these alternative names can make the program more flexible and reusable.

[Edit] History of Programming Languages

When computers first appeared in the 1940s, programmers had to control them manually. At that time, computers were very expensive, and the only person who thought of using programming language to solve problems was German engineer Konrad Zuse.

Decades later, the price of computers has dropped sharply, and computer programs have become more and more complicated. In other words, development time is far more precious than running time.

Therefore, the new integrated and visual development environment is becoming more and more popular. They reduce the time, money (and brain cells) spent. With a few keystrokes, you can use a whole piece of code. This also benefits from a reusable program code base.

[Edit] Common programming languages

APL, a+ and j

active server pages

language

assembler language

AWK

Basic、Fortran

mentally-retarded person

C、C++

clipper

Commercial computer programming language

database