In Unicode the capital K is codepoint U+004B and the lower case k is U+006B.
The ASCII code for capital K is 75 and for lowercase k is 107; or in binary 01001011 and 01101011, correspondingly.
The EBCDIC code for capital K is 210, and for lowercase k, 146.
The numeric character references in HTML and XML are "K" and "k" for upper and lower case respectively.
[edit] See also