编辑“︁A.out”︁（章节）

== 应用 ==

在UNIX第一版中，就出现了给[[PDP-7]]和[[PDP-11]]用的''a.out''格式。<ref>{{cite manual | title = a.out — assembler and link editor output | author = [[Dennis Ritchie]] | date = 1971-11-03 | url = http://cm.bell-labs.com/cm/cs/who/dmr/man51.pdf | format = PDF | publisher = Bell Labs | accessdate = 2006-11-24 | deadurl = yes | archiveurl = https://web.archive.org/web/20061207011324/http://cm.bell-labs.com/cm/cs/who/dmr/man51.pdf | archivedate = 2006-12-07 }}</ref>之后它被[[UNIX System V]]中的[[COFF]]所取代，而COFF最后也被[[SVR4]]中的[[ELF格式]]所取代。

尽管[[BSD]]曾经沿用了一段时间的''a.out''格式，但较新的BSD系统都已切换到ELF。[[NetBSD|NetBSD/i386]]在1.5版中正式从''a.out''切换到ELF，[[FreeBSD|FreeBSD/i386]]则是在2.2到3.0的转换中切换到ELF的。

''a.out''格式对[[调试]]信息的支持是由符号表中称作“[[stabs]]”的特殊项实现的。许多[[COFF]]和[[可執行與可鏈接格式|ELF]]变体中也用到了stabs格式。

[[Linux]]在1.2版内核之前也曾使用''a.out''格式（实验性的1.1.52版中加入了对ELF的支持），在此之后也被ELF取代了。 <ref>{{cite web |url=http://www.ibiblio.org/pub/historic-linux/distributions/slackware/3.9/docs/ELF-HOWTO |title=The Linux ELF HOWTO (v1.29) |author=Daniel Barlow |date=14 July 1996 |accessdate=2008-03-28 |deadurl=yes |archiveurl=https://web.archive.org/web/20040713171954/http://www.ibiblio.org/pub/historic-linux/distributions/slackware/3.9/docs/ELF-HOWTO |archivedate=2004-07-13 }}</ref>Linux之所以转向ELF，或多或少是因为在此平台上构建一个''a.out''格式的函式库所需的复杂性过高：因为Linux中''a.out''的ld.so不能重定位共享函式库，所以需要一个中央机构来注册各个函式库的虚拟地址域。<ref>{{cite paper | title = How To Write Shared Libraries | author = Ulrich Drepper | section = 1.1  A Little Bit of History | version = 4.0 | date = 2006-08-20 | url = http://people.redhat.com/drepper/dsohowto.pdf | format = PDF | accessdate = 2007-06-20 | quote = When introducing shared libraries certain design decisions had to be made to work in the limitations of a.out. (...) For all these reasons and more, Linux converted early on to using ELF (Executable Linkage Format) as the binary format. | archive-date = 2007-06-16 | archive-url = https://web.archive.org/web/20070616175733/http://people.redhat.com/drepper/dsohowto.pdf | dead-url = yes }}</ref>一些BSD变体在[[Linux]]被迫转向ELF之后仍然用了很久的''a.out''格式，因为相比于Linux，BSD的''a.out''略微更灵活一些。<ref>{{cite web | title = BSD Myths: BSD uses the a.out executable format, which is outdated technology | accessdate = 2007-04-10 | url = http://people.freebsd.org/~nik/advocacy/myths.html#aout | archive-date = 2007-04-17 | archive-url = https://web.archive.org/web/20070417095655/http://people.freebsd.org/~nik/advocacy/myths.html#aout | dead-url = no }}</ref>由于a.out格式的相关代码已经老旧并缺乏维护，而且已经几乎没有使用a.out格式的存在，5.1版内核决定移除相应的功能支持。<ref>{{cite web
 |title        = x86: Deprecate a.out support
 |author       = Borislav Petkov
 |date         = 5 March 2019
 |accessdate   = 5 March 2019
 |url          = https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eac616557050737a8d6ef6fe0322d0980ff0ffde
 |quote        = Linux supports ELF binaries for ~25 years now. a.out coredumping has bitrotten quite significantly and would need some fixing to get it into shape again but considering how even the toolchains cannot create a.out executables in its default configuration, let's deprecate a.out support and remove it a couple of releases later, instead.
 |archive-date = 2020-09-19
 |archive-url  = https://web.archive.org/web/20200919224019/https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eac616557050737a8d6ef6fe0322d0980ff0ffde
 |dead-url     = no
}}</ref>

[[MINIX 3]]仍将''a.out''作为二进制文件的格式，但其不支持[[函式库|共享函式库]]。