Below is a conversion table with decimal numbers next to their binary and hexadecimal equivalents. The matching ASCII characters are listed as well.

If none of these words mean anything to you, jump to the bottom of this page for more information on these systems.

Binary numbers

A computer number system that consists of 2 numerals, 0 and 1. It is sometimes called base-2.

Since computers do not have 10 fingers, all the counting within the computer itself is done using only 2 numerals: 0 and 1 (or “on” and “off” or “false” and “true”).

Hexadecimal numbers

The hexadecimal system (hex for short) uses numbers from 0 to 15. It starts off like the decimal system: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 but then comes A which equals 10 and then B, C, D, E and F (which of course equals 15). The next number is 10 which is actually 16 in decimal and so on….
Because it can be impossible to distinguish between a hex and a decimal number (is that 25 a decimal 25 or is it 25 in hex which equals 37 decimal?) it is customary to put a lower case h after each hex number.

ASCII

ASCII stands for American Standard Code for Information Interchange. It is a standard that was defined in 1965 to allow computers to exchange information, regardless of the manufacturer.

The ASCII character set consists of 128 decimal numbers, ranging from 0 through 127, assigned to letters, numbers, punctuation marks and the most common special characters. For instance, if you look at the table, you can see that number 65 represents a capital A.

The character set is called 7-bit ASCII. All computer systems also use numbers 129 through 255 to represent additional characters but this list is not really standardized so differences can creep up. The only semi-standard is the so-called extended ASCII character set launched by IBM in 1981. This lack of standardization explains why some French characters in your PC document turned into little squares when you opened the file on a Mac.

The competing standard which has virtually disappeared is EBCDIC, developed by IBM.

Because 256 characters are not sufficient to represent all characters used in Asian languages and to solve the annoying compatibility problems, a new standard has emerged. The “Unicode” character set contains more than 32000 characters.