Alternatively referred to as caps and capital, uppercase (UC) 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 just 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 while online 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 does 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.
Using the uc command
my $example = "hello world";
$example = ucfirst($example);
$example = uc($example);
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".