Extended BCD Instruction Code. IBM's (suite of) character encoding(s). If you're not dealing with IBM systems or legacy data, it is almost certainly better to use one of the encodings that have evolved from ASCII instead.
Interestingly enough, EBCDIC was not an IBM invention; it was developed by the same committee that developed ASCII, and the code sets are closely related. EBCDIC was designed for easy encoding on Hollerith cards and decimal computers, while ASCII was designed for paper tape and binary computers.
The fact that the alphabet is disconnected in EBCDIC comes from the fact that it's tied to card code. The most significant nybble of an EBCDIC character represents the zone punches (12, 11, 0) and the least significant one represents the numeric punches (1-9). There's a weird special case surrounding zero, blank, and null.
RS: Here is a list from Oracle's SQL Language Reference Manual:
Decimal Symbol Decimal Symbol 64 blank 108 % 74 cent sign* 109 _ 75 . 110 > 76 < 111 ? 77 ( 122 : 78 + 123 # 79 | 124 @ 80 & 125 ' 90 ! 126 = 91 $ 127 " 92 * 129..137 a - i 93 ) 145..153 j - r 94 ; 162..169 s - z 95 NOT sign* 193..201 A - I 96 - 209..217 J - R 97 / 226..233 S - Z 107 , 240..249 0 - 9 *: characters not in ASCII. NOT sign is a dash with short hook down.