The true definition of a code page is a key that describes each available character in a specific character set. This technical definition is slowly being supplanted by a non-technical definition. In this case, a code page is the page of programing that is displayed when looking at the inner workings of a webpage, computer file or program. The original definition has been in use for decades, but the new usage gains ground all the time as more non-technical computer users enter the picture.
In the original definition, a code page is almost like the key to a secret code. It will have a list of numerical values that corresponds to a specific character in a non-machine language. For example, ‘0040’ may correspond to the character ‘@.’ This allows a computer to use numbers and humans to use words, but they both have access to the same information.
A code page is typically arranged in a table that has a specific number of columns and rows. A hexadecimal, or 16-bit, code page will have 16 columns and 16 rows making a total of 256 total spaces. Other common sizes are 8x8, or 8-bit, and the common 8-bit variation of 7x7. The larger the table, the more characters the set may possess and the more complex the overall encoding may be.
There are many different code sets in common use today. The most common codes are Unicode and American Standard Code for Information Interchange (ASCII), but each language has its own version of the code for use with each specific alphabet. Some languages, such as Finnish or Japanese, have extremely complex sets to account for their isolated languages. In addition, major computer hardware companies, such as IBM®, or operating system companies, such as Microsoft®, use their own proprietary code pages. These companies need to maintain a different page for each language as well.
The newer definition relies on the common usage of the word code. In this case, code refers to any type of programming regardless of its origin, usage or language. It is just as correct to use code to describe computer assembly language as the inner working of a webpage. This generic code is often encountered by people with low technical knowledge as they go about using a computer system.
This code is often displayed in error messages and in web browsers. These pages are often blocks of neutral background, usually cream or white, with what appears to be long lines of random text. These are often called code pages since they contain the generic code on a page like background.