Editing EBCDIC (section)

== Compatibility with ASCII ==
{{More citations needed section|date=November 2022}}
There were numerous difficulties to writing software that would work in both ASCII and EBCDIC.
* The gaps between letters made simple code that worked in ASCII fail on EBCDIC. For example {{code|1=for (c = 'A'; c <= 'Z'; ++c) putchar(c);|lang=c}} would print the alphabet from A to Z if ASCII is used, but print 41 characters (including a number of unassigned ones) in EBCDIC.
* Sorting EBCDIC put lowercase letters before uppercase letters and letters before numbers, exactly the opposite of ASCII.
* Most programming languages and file formats and network protocols designed for ASCII used available punctuation marks (such as the curly braces {{char|{{(}}}} and {{char|{{)}}}}) that did not exist in EBCDIC, making translation to EBCDIC systems difficult. Workarounds such as [[digraphs and trigraphs (programming)|trigraphs]] were used.<ref>{{cite web|title=Rationale for International Standard – Programming Languages – C|version=Revision 5.10|date=April 2003|url=http://www.open-std.org/jtc1/sc22/wg14/www/C99RationaleV5.10.pdf#page=204|at=§ MSE.4: Support for invariant ISO/IEC 646|access-date=2022-11-24 |url-status=live|archive-url=https://web.archive.org/web/20160606072228/http://www.open-std.org/jtc1/sc22/wg14/www/C99RationaleV5.10.pdf|archive-date=2016-06-06}}</ref> Conversely EBCDIC had a few characters such as {{char|¢}} ([[Penny (United States coin)|US cent]]) that were used on IBM systems and could not be translated to ASCII.
* The most common newline convention used with EBCDIC is to use a [[Newline|NEL]] (NEXT LINE) code between lines. Converters to other encodings often replace NEL with [[Line feed|LF]] or [[CR/LF]], even if there is a NEL in the target encoding. This causes the LF and NEL to translate to the same character and be unable to be distinguished.
* If seven-bit ASCII was used, there was an "unused" high bit in 8-bit bytes, and many pieces of software stored other information there. Software would also pack the seven bits and discard the eighth, such as packing five seven-bit ASCII characters in a [[36-bit]] word.<ref>{{cite book|url=http://www.bitsavers.org/pdf/dec/pdp10/1970_PDP-10_Ref/1970PDP10Ref_Part2.pdf|title=PDP-10 Reference Handbook, Book 2: Assembling the Source Program|page=221|publisher=[[Digital Equipment Corporation]]}}</ref> On the [[PDP-11]], bytes with the high bit set were treated as negative numbers, behavior that was copied to [[C (programming language)|C]], causing unexpected problems if the high bit was set. These all made it difficult to switch from ASCII to the 8-bit EBCDIC (and also made it difficult to switch to 8-bit [[extended ASCII]] encodings).