Lower case refers to the smaller of the two cases (i.e., forms) of letters that characterize most modern alphabets, particularly those based on the Roman and Greek alphabets.
An alphabet is the ordered, standardized set of letters that is used to write or print a written language. A letter is a character in an alphabet that represents one, or several, phonemes (i.e., the fundamental sounds of a spoken language) and/or that is used in combinations with other letters to represent one, or several, phonemes. A character is any letter, symbol or mark that is used in writing or printing a language.
The Roman alphabet was originally used by the ancient Romans to write their Latin language more than 2000 years ago. English and many other languages, including all Western European languages, have writing systems that are based on the Roman alphabet.
The Roman alphabet originally contained only a single form of letters, which today are referred to as upper case letters or, more commonly, capital letters. (Moreover, there was no spacing between words, nor was there any punctuation!)
Lower case letters originated from manuscript writing in the Middle Ages. Writing with pens caused the original, largely angular, characters to become rounder and simpler, and it also resulted in some of them extending beyond the lower boundary that restrained capital letters. Lower case became irresistible to manuscript writers because it was faster to write, it was easier to read and it conserved space on the costly parchment (which was made from animal skins and used instead of paper).
As it had already been common to make the first letter of each sentence as well as the first letter of each noun slightly larger than the other letters, it was a fairly logical progression to retain upper case letters for those situations and use lower case letters for almost everything else.
If an alphabet has case, all of its letters generally have both upper and lower case forms. Both forms of each letter are, for most purposes, considered to be the same letter; that is, they have the same name and the same pronunciation and they are treated (virtually) identically when sorting in alphabetical order.
Standardized rules for determining which case should be used in a given context began to emerge in the early eighteenth century. In modern English, upper case is used for (1) the first letter of each sentence, (2) the first letter of each proper noun (i.e., the name of a person, place, organization, etc.), (3) all letters in initials and (4) all letters in acronyms. The capitalization rules for German are similar, except that the older practice of using upper case for the first letter of every noun, rather than just for proper nouns, has been retained.
The terms lower case and upper case originated from the way that type (i.e., individual letters that were cast from special metal alloys for use in printing) was stored in the days of hand typesetting. The type was sorted by letter and kept in specially designed wooden or metal cases, with separate cases for capital and small letters. Usually the two cases were placed one above the other on a rack on the typesetter's desk, with the case containing the capital letters (i.e., the upper case) positioned above that containing the small letters (i.e., the lower case).
Advantages of Lower Case
The invention and application of lower case letters has been highly beneficial to the reading and writing of text. The most important benefit is that it can be easier on the eyes and can make text easier to read.
This is because of the greater variety of shapes of lower case letters as compared with upper case letters. In particular, nine lower case letters (b d f h i j k l t) have segments (or dots) that extend above the upper base line for the main body of lower case letters, and five letters (g j p q y) extend below the lower base line for the main body of all characters. The variety of shapes, and the consequent greater ease of reading, is further increased by the occasional use of upper case letters (e.g., the first letters in sentences and in proper nouns) in text that is composed of mostly lower case letters.
A second advantage is that text that is written predominantly in lower case occupies less space than text that is written in all upper case when using proportional fonts. A proportional font is one in which the horizontal space occupied by a letter is proportional to the width of the letter. Most common fonts today are proportional, although a few, such as Courier (which was commonly used on typewriters and is still available on most computers) are monospaced, i.e., every letter occupies the same horizontal space.
This space reduction can be particularly convenient in a computer context when using long commands, including multiple commands that are combined through the use of pipes on Unix-like operating systems. This is because it reduces the need for wrapping such long commands or pipelines of commands to multiple lines, thus improving readability and making it easier to correct errors in or to make changes to such commands prior to executing (i.e., running) them.
An operating system, programming language or application program is said to be case-sensitive if it differentiates between upper case and lower case letters. For example, in a case-sensitive operating system, files with the names alice and Alice would be treated as two completely different files.
Most modern operating systems and programming languages are case sensitive. Unix-like operating systems are case-sensitive for almost everything, not just file names.
One notable exception is the apropos command, which displays a list of all topics in the man pages (i.e., pages in the standard manual that is built into Unix-like operating systems) that are related to the subject of a query. apropos was purposely designed with a lack of case sensitivity in order to enhance its convenience and efficiency, just as has been done with the Google, Yahoo and other Internet search engines (which are almost always run on case-sensitive Unix-like operating systems, particularly Linux).
Older operating systems such as MS-DOS are not case sensitive. With MS-DOS, it is a convention, although not required, to use upper case letters for commands and file names.
Microsoft Windows 95 is likewise case-insensitive, but it is case-preserving. This means that although file names with different capitalization, such as alice and Alice, are considered to be identical, the names are stored in the system just as they were typed into it.
HTML (hypertext markup language), the basic language for writing web pages, is case insensitive. However, web page programming is moving in the direction of becoming case sensitive with the introduction of HTML's successor, XHTML (eXtensible HTML), which makes specific recommendations (but not yet mandatory requirements) about the use of case. Interestingly, these recommendations follow the Unix concept of using lower case in most situations.
Modern character encoding systems such as ASCII (which is the default standard for most computers) and Unicode (which attempts to provide a unique encoding for every character used by the world's languages) assign different code numbers to lower case letters and their upper case counterparts, just as they assign different code numbers to completely different letters. This should not necessarily be interpreted as meaning that such encoding systems are taking a position in favor of case sensitivity for operating systems, programming languages, etc. Rather, it could be seen as merely a means of taking a neutral stance on the issue and thus making it possible for the developers of operating systems and programming languages which use such character encoding systems to make their own decisions regarding case sensitivity.
Lower Case and the Unix Philosophy
One of the tenets of the Unix philosophy, on which the Linux philosophy is based, is that lower case should be used for almost everything. There are several reasons for this.
UNIX was designed to be simple and easy to use. Despite its reputation of being complex and difficult to use, it represented a major advance in simplicity and user friendliness as compared with other operating systems that were available at the time of its development. In fact, even today in many respects Unix-like operating systems are simpler and easier for computer professionals to use than are some of the popular alternatives.
The advantages of using mostly lower case on computers are similar to those of using it in other situations. Most importantly, it is easier to read. Also, it helps save space on what can sometimes be smaller-than-desired display screens. Moreover, distinguishing between lower case and upper case characters increases the total number of unique characters that are available for use in file names, commands, etc., thereby adding to system flexibility.
There are several situations in Unix-like operating systems in which upper case is used, in addition to its normal usage in text. However, these exceptions do not contradict the basic Unix philosophy; rather, they strengthen it by enhancing its overall flexibility and ease of use.
Environment variables, by convention, are normally given names that consist entirely of upper case letters in order to easily distinguish them from files and commands. Environmental variables are a class of variables that tell the shell (a program that provides the traditional, text-only user interface for Unix-like operating systems) and scripts (small programs designed to be interpreted by the shell) how to behave.
Upper case is also used for some command options. Options are used to fine tune (i.e., customize) commands, and each is usually denoted by a single, lower case letter. However, many commands also have additional options that are represented by upper case letters in order to distinguish them from those with lower case letters.
For example, the wc command, whose default behavior is to count the number of lines, words and characters that are contained in a text file or in text entered from the keyboard, has an -l option, that tells it to show only the number of lines, and an -L option, that tells it to display only the number of letters in the longest line.
Another of the few recommended uses for upper case in Unix-like operating systems is in passwords. This is because using a mixture of lower and upper case as well as other characters (e.g., punctuation) makes it more difficult for passwords to be guessed by password cracking programs.
Created December 30, 2004.