Interestingly, IBM was a chief proponent of the ASCII standardization committee. However, IBM did not have time to prepare ASCII peripherals (such as card punch machines) to ship with its System/360 computers, so the company settled on EBCDIC at the time. The System/360 became wildly successful, and thus so did EBCDIC.
All IBM mainframe peripherals and operating systems (except Linux on zSeries or iSeries) use EBCDIC as their inherent encoding. but software can translate to and from other encodings. Many hardware peripherals provide translation as well and modern mainframes (such as IBM zSeries) include processor instructions, at the hardware level, to accelerate translation between character sets.
At the time it was devised, EBCDIC made it relatively easy to enter data into a computer with punch cards. Since punch cards are no longer used on mainframes, EBCDIC is used in modern mainframes solely for backwards compatibility. It has no real technical advantage over ASCII-based code pages such as the ISO-8859 series or Unicode. There are some technical niceties in each, e.g., ASCII and EBCDIC both have one bit which indicates upper or lower case. But there are some aspects of EBCDIC which make it much less pleasant to work with than ASCII (such as a non-contiguous alphabet). As with single-byte extended ASCII codepages, most EBCDIC codepages only allow up to 2 languages (English and one other language) to be used in a database or text file.
Where true support for multilingual text is desired, a system supporting far more characters is needed. Generally this is done with some form of Unicode support. There is an EBCDIC Unicode Transformation Format called UTF-EBCDIC proposed by the Unicode consortium, but it is not intended to be used in open interchange environments and, even on EBCDIC-based systems, it is almost never used. IBM mainframes support UTF-16, but they do not support UTF-EBCDIC natively.
Arabic EBCDIC versions are typically in presentation order, in left to right order as displayed by an older mainframe or line printer, rather than in the right to left logical order used by modern encodings such as Unicode.
The Jargon file 4.4.7 gives the following definition:
Another popular complaint is that the EBCDIC alphabetic characters follow an archaic punch card encoding rather than a linear ordering like ASCII. The upshot of this is that incrementing the character code for "I" does not produce the code for "J", and likewise there is a gap between the codes for "R" and "S". Thus programming a simple control loop to cycle through only the alphabetic characters is problematic.
These incompatibilities were also the source of many jokes. A popular one went: