What is a computer programming language?

Question

At the risk of sounding naive, I ask this question in search of a deeper understanding of the concept of programming languages in general. I write this question for my own e

Answer 1

One thing a lot of "IT" types forget is that there are 2 types of computer programming languages:

1. Software programming languages: C, Java, Perl, COBAL, etc.

2. Hardware programming languages: VHDL, Verilog, System Verilog, etc.

Answer 2

This question is very broad. My favorite definition is that a programming language is a means of expressing computations

• Precisely
• At a high level
• In ways we can reason about them

By computation I mean what Turing and Church meant: the Turing machine and the lambda calculus have equivalent expressive power (which is a theorem), and the Church-Turing hypothesis (which is a conjecture) says roughly that there's no more powerful notion of computation out there. In other words, the kinds of computations that can be expressed in any programming languages are at best the kinds that can be expressed using Turing machines or lambda-calculus programs—and some languages will be able to express only a subset of those calculations.

This definition of computation also encompasses your friendly neighborhood hardware, which is pretty easy to simulate using a Turing machine and even easier to simulate using the lambda calculus.

Expressing computations precisely means the computer can't wiggle out of its obligations: if we have a particular computation in mind, we can use a programming language to force the computer to perform that computation. (Languages with "implementation defined" or "undefined" constructs make this task more difficult. Programmers using these languages are often willing to settle for—or may be unknowingly settling for—some computation that is only closely related to the computation they had in mind.)

Expressing computation at a high level is what programming langauges are all about. An important reason that there are so many different programming languages out there is that there are so many different high-level ways of thinking about problems. Often, if you have an important new class of problems to solve, you may be best off creating a new programming language. For example, Larry Wall's writing suggests that solving a class of problems called "systems administration" was a motivation for him to create Perl.

(Another reason there are so many different programming languages out there is that creating a new language is a lot of fun, and anyone can learn to do it.)

Finally, many programmers want languages that make it easy to reason about programs. For example, today a student of mine implemented a new algorithm that made his program run over six times faster. He had to reason very carefully about the contents of C arrays to make sure that the new algorithm would do the same job the old one did. Luckily C has decent tools for reasoning about programs, for example:

• A change in a[i] cannot affect the value of a[i-1].

My student also applied a reasoning principle that isn't valid in C:

• The sum of of a sequence unsigned integers will be at least as large as any integer in the sequence.

This isn't true in C because the sum might overflow. One reason some programmers prefer languages like Standard ML is that in SML, this reasoning principle is always valid. Of languages in wide use, probably Haskell has the strongest reasoning principles Richard Bird has developed equational reasoning about programs to a high art.

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I will not attempt to address all the tangential details that follow your opening question. But I hope you will get something out of an answer that aims to give a deeper understanding, as you asked, of a fundamental question about programming languages.

Answer 3

As a friend taught me about computer languages, a language is a world. A world of communication with that machine. It is world for implementing ideas, algorithms, functionality, as Alonzo and Alan described. It is the technical equivalent of the mathematical structures that the aforementioned scientists built. It is a language with epxressions and also limits. However, as Ludwig Wittgenstein said "The limits of my language mean the limits of my world", there are always limitations and that's how one chooses it's language that fits better his needs.

It is a generic answer... some thoughts actually and less an answer.

Answer 4

See "Programming Considered as a Human Activity." EWD 117. http://www.cs.utexas.edu/~EWD/transcriptions/EWD01xx/EWD117.html

Also See http://www.csee.umbc.edu/331/current/notes/01/01introduction.pdf

Answer 5

There are many definitions to this but what I prefer is:

Computer programming is programming that helps to solve a particular technical task/problem.

There are 3 key phrases to look out for:

You: Computer will do what you (Programmer) told it to do.

Instruct: Instruction is given to the computer in a language that it can understand. We will discuss that below.

Problem: At the end of the day computers are tools (Complex). They are there to make out life simpler.

The answer can be lengthy but you can find more about computer programming