Updated: 11/13/2018 by Computer Hope

Uppercase text exampleAlternatively referred to as caps and capital, and sometimes abbreviated as UC, uppercase is a typeface of larger characters. For example, a, b, and c is lowercase, and A, B, and C is uppercase.

Tip: It is bad etiquette to have everything you type in ALL UPPERCASE CHARACTERS. When reading anything typed in all caps, most readers assume you are YELLING or find the text hard to read.

Why is capitalization important?


Passwords are case-sensitive to add an extra level of security. If your caps lock key was enabled while creating your password and disabled while trying to log in the next day, you would not be able to log into your account.

File names, directories, and paths

When dealing with file names, directories, and paths in many operating systems and paths they are case-sensitive. For example, in Microsoft Windows nothing is case-sensitive. However, when uploading a file to the Internet, the files and directories become case-sensitive. For example, the file name of this web page is "uppercase.htm" and must be typed in all lowercase in the URL while online. However, if you were viewing the file locally on a Windows computer, the capitalization would not matter.


When dealing with computer measurements and other measurements capitalization is important for identifying the exact type of measurement. For example, "Mb" (short for megabit) and "MB" (short for megabyte) are two different types of measurements with different values.


Command line commands in operating systems like Linux are case-sensitive, which means if you typed "Ls" to list file you would get an error since the ls command is all lowercase.

Programming functions

In earlier programming languages like Fortran, the keywords and the names of data objects were required to be written in all uppercase because punch card machines did not have a Shift key.


To help differentiate an acronym from other words in a sentence, they are typed in uppercase. For example, the acronym RAM is typed in all uppercase to help identify the word as an acronym.

Using the uc function

Many programming and scripting languages use the uc function to convert a variable into uppercase. For example, in the example below is how the uc and ucfirst functions can be used in Perl.

my $example = "hello world";
print "$example\n";
$example = ucfirst($example);
print "$example\n";
$example = uc($example);
print "$example\n";

In the above example, the $example variable is set to all lowercase. The third line uppercases the first character making the text "Hello world," and the fifth line uppercases the whole string making the text "HELLO WORLD."

What is the difference between capitalize and uppercase?

Capitalize is used when you're describing the first letter of a word or a single letter. For example, the first letter in this sentence is capitalized. Uppercase is used to describe a word with every letter being capitalized. For example, the acronym CPU is in uppercase.

When should I capitalize text?

Below is a list of some of the general rules that should be followed when capitalizing words.

  • Always capitalize the first word of a sentence.
  • If the word is a proper noun or derived from a proper noun, the first letter should be capitalized. For example, a name, book, brand, movie, place, product, and trademark are proper nouns and should be capitalized.
  • Capitalize the first letter of a quote unless it is part of the sentence.
  • Roads and streets should be capitalized.
  • A person's title (not occupation) before their name should be capitalized.

Below is a list of times capitalization should not be used.

  • Never user uppercase for emphasis. Instead, italicize any text you want to emphasize.
  • When writing the full form of an acronym, each word of the acronym should be lowercase unless it is a proper noun.
  • Do not capitalize the word the when used before a proper noun.

Should titles and headings be capitalized?

With formal writing, the titles and headings should use title case. All other forms of writing should follow the rules set by the used style guide. For example, Computer Hope follows the Microsoft Manual of Style and uses sentence case for its headings.

Should I use "uppercase" or "upper case" in my writing?

Both "uppercase" and "upper case" are correct. However, you should only use one form in your writing. According to The Associated Press Stylebook and the Microsoft Manual of Style, you should write "uppercase" as one word when being used as an adjective and as a noun.

Caps lock, Case, Case-sensitive, Character, Computer acronyms, Font, Lowercase, Proper case, Title case, Typography terms