High-level programming language
Encyclopedia
A high-level programming language is a programming language
with strong abstraction
from the details of the computer. In comparison to low-level programming language
s, it may use natural language
elements, be easier to use, or be from the specification of the program, making the process of developing a program simpler and more understandable with respect to a low-level language. The amount of abstraction provided defines how "high-level" a programming language is.
The first high-level programming language to be designed for a computer was Plankalkül
, created by Konrad Zuse
. However, it was not implemented in his time, and his original contributions were isolated from other developments.
, complex arithmetic or boolean expressions, subroutines and functions, loops, thread
s, locks, and other abstract computer science concepts, with a focus on usability
over optimal program efficiency. Unlike low-level assembly languages, high-level languages have few, if any, language elements that translate directly into a machine's native opcodes. Other features, such as string handling routines, object-oriented language features, and file input/output, may also be present.
of a program mostly in a high-level language can be hand-coded in assembly language
, leading to a much faster or more efficient optimised program.
However, with the growing complexity of modern microprocessor
architectures, well-designed compilers for high-level languages frequently produce code comparable in efficiency to what most low-level programmers can produce by hand, and the higher abstraction may allow for more powerful techniques providing better overall results than their low-level counterparts in particular settings.
, and similar languages, were most often considered "high-level", as it supported concepts such as expression evaluation, parameter
ised recursive functions, and data types and structures, while assembly language
was considered "low-level". Many programmers today might refer to C as low-level, as it lacks a large runtime-system (no garbage collection, etc.), basically supports only scalar operations, and provides direct memory addressing. It, therefore, readily blends with assembly language and the machine level of CPUs and microcontroller
s.
Assembly language may itself be regarded as a higher level (but often still one-to-one if used without macros) representation of machine code
, as it supports concepts such as constants and (limited) expressions, sometimes even variables, procedures, and data structure
s. Machine code
, in its turn, is inherently at a slightly higher level than the microcode
or micro-operation
s used internally in many processors.
Interpreted : Interpreted language
s are read and then executed directly, with no compilation stage. A program called an interpreter reads each program line following the program flow, converts it to machine code, and executes it; the machine code is then discarded, to be interpreted anew if the line is executed again.
Compiled : Compiled language
s are transformed into an executable form before running. There are two types of compilation:
Translated : A language may be translated into a lower-level programming language for which native code compilers are already widely available. The C programming language
is a common target for such translators.
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
with strong abstraction
Abstraction (computer science)
In computer science, abstraction is the process by which data and programs are defined with a representation similar to its pictorial meaning as rooted in the more complex realm of human life and language with their higher need of summarization and categorization , while hiding away the...
from the details of the computer. In comparison to low-level programming language
Low-level programming language
In computer science, a low-level programming language is a programming language that provides little or no abstraction from a computer's instruction set architecture. Generally this refers to either machine code or assembly language...
s, it may use natural language
Natural language
In the philosophy of language, a natural language is any language which arises in an unpremeditated fashion as the result of the innate facility for language possessed by the human intellect. A natural language is typically used for communication, and may be spoken, signed, or written...
elements, be easier to use, or be from the specification of the program, making the process of developing a program simpler and more understandable with respect to a low-level language. The amount of abstraction provided defines how "high-level" a programming language is.
The first high-level programming language to be designed for a computer was Plankalkül
Plankalkül
Plankalkül is a computer language designed for engineering purposes by Konrad Zuse between 1943 and 1945. It was the first high-level non-von Neumann programming language to be designed for a computer. Also, notes survive with scribblings about such a plan calculation dating back to 1941...
, created by Konrad Zuse
Konrad Zuse
Konrad Zuse was a German civil engineer and computer pioneer. His greatest achievement was the world's first functional program-controlled Turing-complete computer, the Z3, which became operational in May 1941....
. However, it was not implemented in his time, and his original contributions were isolated from other developments.
Features
"High-level language" refers to the higher level of abstraction from machine language. Rather than dealing with registers, memory addresses and call stacks, high-level languages deal with variables, arrays, objectsEntity
An entity is something that has a distinct, separate existence, although it need not be a material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is animate.An entity could be viewed as a set...
, complex arithmetic or boolean expressions, subroutines and functions, loops, thread
Thread (computer science)
In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process...
s, locks, and other abstract computer science concepts, with a focus on usability
Usability
Usability is the ease of use and learnability of a human-made object. The object of use can be a software application, website, book, tool, machine, process, or anything a human interacts with. A usability study may be conducted as a primary job function by a usability analyst or as a secondary job...
over optimal program efficiency. Unlike low-level assembly languages, high-level languages have few, if any, language elements that translate directly into a machine's native opcodes. Other features, such as string handling routines, object-oriented language features, and file input/output, may also be present.
Abstraction penalty
Stereotypically, high-level languages make complex programming simpler, while low-level languages tend to produce more efficient code. Abstraction penalty is the barrier that prevents high-level programming techniques from being applied in situations where computational resources are limited. High-level programming features like more generic data structures, run-time interpretation, and intermediate code files often result in slower execution speed, higher memory consumption, and larger binary program size. For this reason, code which needs to run particularly quickly and efficiently may require the use of a lower-level language, even if a higher-level language would make the coding easier. In many cases, critical portionsCritical Path
Critical Path may refer to:*The Critical Path, the longest necessary path through a network of activities when respecting their interdependencies, which may be identified with the Program Evaluation and Review Technique and the Critical path method...
of a program mostly in a high-level language can be hand-coded in assembly language
Assembly language
An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
, leading to a much faster or more efficient optimised program.
However, with the growing complexity of modern microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
architectures, well-designed compilers for high-level languages frequently produce code comparable in efficiency to what most low-level programmers can produce by hand, and the higher abstraction may allow for more powerful techniques providing better overall results than their low-level counterparts in particular settings.
Relative meaning
The terms high-level and low-level are inherently relative. Some decades ago, the C languageC (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, and similar languages, were most often considered "high-level", as it supported concepts such as expression evaluation, parameter
Parameter
Parameter from Ancient Greek παρά also “para” meaning “beside, subsidiary” and μέτρον also “metron” meaning “measure”, can be interpreted in mathematics, logic, linguistics, environmental science and other disciplines....
ised recursive functions, and data types and structures, while assembly language
Assembly language
An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
was considered "low-level". Many programmers today might refer to C as low-level, as it lacks a large runtime-system (no garbage collection, etc.), basically supports only scalar operations, and provides direct memory addressing. It, therefore, readily blends with assembly language and the machine level of CPUs and microcontroller
Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
s.
Assembly language may itself be regarded as a higher level (but often still one-to-one if used without macros) representation of machine code
Machine code
Machine code or machine language is a system of impartible instructions executed directly by a computer's central processing unit. Each instruction performs a very specific task, typically either an operation on a unit of data Machine code or machine language is a system of impartible instructions...
, as it supports concepts such as constants and (limited) expressions, sometimes even variables, procedures, and data structure
Data structure
In computer science, a data structure is a particular way of storing and organizing data in a computer so that it can be used efficiently.Different kinds of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks...
s. Machine code
Machine code
Machine code or machine language is a system of impartible instructions executed directly by a computer's central processing unit. Each instruction performs a very specific task, typically either an operation on a unit of data Machine code or machine language is a system of impartible instructions...
, in its turn, is inherently at a slightly higher level than the microcode
Microcode
Microcode is a layer of hardware-level instructions and/or data structures involved in the implementation of higher level machine code instructions in many computers and other processors; it resides in special high-speed memory and translates machine instructions into sequences of detailed...
or micro-operation
Micro-operation
In computer central processing units, micro-operations are detailed low-level instructions used in some designs to implement complex machine instructions .Various forms of μops have long been the basis for traditional microcode routines used to simplify the implementation of a...
s used internally in many processors.
Execution models
There are three models of execution for modern high-level languages:Interpreted : Interpreted language
Interpreted language
Interpreted language is a programming language in which programs are 'indirectly' executed by an interpreter program. This can be contrasted with a compiled language which is converted into machine code and then 'directly' executed by the host CPU...
s are read and then executed directly, with no compilation stage. A program called an interpreter reads each program line following the program flow, converts it to machine code, and executes it; the machine code is then discarded, to be interpreted anew if the line is executed again.
Compiled : Compiled language
Compiled language
A compiled language is a programming language whose implementations are typically compilers , and not interpreters ....
s are transformed into an executable form before running. There are two types of compilation:
-
- Machine code generation : Some compilers compile source code directly into machine codeMachine codeMachine code or machine language is a system of impartible instructions executed directly by a computer's central processing unit. Each instruction performs a very specific task, typically either an operation on a unit of data Machine code or machine language is a system of impartible instructions...
. This is the original mode of compilation, and languages that are directly and completely transformed to machine-native code in this way may be called "truly compiled" languages. - Intermediate representations : When a language is compiled to an intermediate representation, that representation can be optimized or saved for later execution without the need to re-read the source file. When the intermediate representation is saved, it is often represented as byte code. The intermediate representation must then be interpreted or further compiled to execute it. Virtual machineVirtual machineA virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
s that execute byte code directly or transform it further into machine code have blurred the once clear distinction between intermediate representations and truly compiled languages.
- Machine code generation : Some compilers compile source code directly into machine code
Translated : A language may be translated into a lower-level programming language for which native code compilers are already widely available. The C programming language
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
is a common target for such translators.
See also
- Abstraction (computer science)Abstraction (computer science)In computer science, abstraction is the process by which data and programs are defined with a representation similar to its pictorial meaning as rooted in the more complex realm of human life and language with their higher need of summarization and categorization , while hiding away the...
- Generational list of programming languagesGenerational list of programming languagesHere, a genealogy of programming languages is shown. Languages are categorized under the ancestor language with the strongest influence. Of course, any such categorization has a large arbitrary element, since programming languages often incorporate major ideas from multiple sources.-ALGOL...
- Low-level programming languageLow-level programming languageIn computer science, a low-level programming language is a programming language that provides little or no abstraction from a computer's instruction set architecture. Generally this refers to either machine code or assembly language...
s - Very high-level programming languageVery high-level programming languageA very high-level programming language is a programming language with a very high level of abstraction, used primarily as a professional programmer productivity tool....
s - Categorical list of programming languagesCategorical list of programming languagesThis is a list of programming languages grouped by category. Some languages are listed in multiple categories.- Array languages :Array programming generalize operations on scalars to apply transparently to vectors, matrices, and higher dimensional arrays.* APL* Chapel* X10* ZPL- Aspect-oriented...
External links
- http://c2.com/cgi/wiki?HighLevelLanguage - The WikiWikiWebWikiWikiWebWikiWikiWeb is a term that has been used to refer to four things: the first wiki, or user-editable website, launched on 25 March 1995 by Ward Cunningham as part of the Portland Pattern Repository ; the Perl-based application that was used to run it, also developed by Cunningham, which was the first...
's article on high-level programming languages