Hextrapolate only allows you to type numbers and letters that are valid for a particular base or text encoding. The allowed characters for some of the common bases and text encodings are shown below:

• Hexadecimal: the digits 0 through 9, as well as the letters a through f
• Decimal: the digits 0 through 9
• Octal: the digits 0 through 7
• Binary: the digits 0 and 1
• ASCII: the 95 printable characters of the ASCII character encoding; these include all the 26 lowercase and uppercase letters of the Roman alphabet, the digits 0 through 9, and a number of punctuation and other characters (see ASCII text encoding for a full listing)

If a character you type is rejected Hextrapolate will show information about it in a tool-tip (see digit error (screenshot) and text encoding error (screenshot)).