Programming Languages

V22.0002

Deena Engel’s class

Programming languages and Natural Languages

They both use:

• syntax (e.g. punctuation)

• grammar (“well formed sentences”)

• parts of speech (reserved words)

• semantics (meanings of variables, objects similar to pronouns)

Natural Languages use:

Syntax: punctuation and spacing

Grammar: to create “well formed sentences” (e.g. subject-verb-object)

Parts of speech: nouns, verbs, adjectives

Semantics: the meaning of the words and what they represent (e.g. in English, “cat” refers to a furry, four-pawed mammal in the Great Cats family)

Programming Languages use:

Syntax: punctuation such as parentheses, braces, brackets, semicolons, etc

Grammar: well-formed structures such as “for loops” and others

Parts of speech: different data types such as integers, characters, dates

Semantics: the meaning of the symbols, e.g. x = 3; or the use of reserved words.

Writing

Steps in writing code in a programming language:

Source code

Compiler

Machine language

Style

• Style counts … in both kinds of languages!

• In natural language … style distinguishes the type of writing e.g. the differences between a sonnet by Shakespeare and my weekly shopping list…

• In a programming language, style is both important to make the program readable and in terms of efficiency

How to use programming languages:

• Natural languages: can be used to tell a story … and other purposes … as well as to give instructions.

• Cookbooks and how-to books provide instructions in a natural language: “mix ½ cup of sugar into the butter”

• The instructions might include decisions: “if these are chocolate chip cookies, add chocolate chips and shredded coconut ; otherwise just add shredded coconut”).

Programming Languages...

Give instructions to the computer!

• A computer program is like a cookie recipe except that the computer follows the instructions!

Programming Languages give instructions:

• Any series of repeated instructions can be called an algorithm. In many cases, the programming language mirrors what you would do if you were doing the task manually:

• Keeping a checkbook: order the amounts by the date of the check; if it’s a check, subtract the amount; if it’s a deposit, add the amount; then print the running total

• Create an index for a textbook: read the text; discard extra words (“the”, “and”); list the important terms and their pages; write it up as an index

Storing Data

Programming languages are also used to track information in logical ways:

For example, one can write a program to creating a database of names, addresses and telephone numbers. We will look at this means of expression as well.