Differences between gcca. out and ELF in linux

Differences between gcca. out and ELF in linux-general Linux technology-Linux programming and kernel information. The following is a detailed description. Recently I used the new version of gcc to find the ELF binary format, and later I found their differences in a book;
A. out is the binary format used by Linux in the past, while ELF is another binary format. It is currently used in many systems.
As the ELF format is growing more elastically than the Linux a. out format in the past, ELF is also more convenient in setting shared libraries.
In 1995, developers of gcc and C library decided to use ELF as the Linux Standard binary format.
However, I found that most gcc compilers still use the. out format.