The source code is written to use an ANSI C99 compatible compiler for portability between Operating Systems.
Hexed is released under the BSD license
The copy command was added to hexed a little while ago. This command has 2 modes of operation: copy (c) or copy overwrite (co).
Copies data from the source inserting it at the destination
-c 100 200 20
This will copy 32 bytes from 0x100 to 0x200 moving everything at 0x200 up by 32 bytes.
Copies data from the source overwriting the destination
-co 100 200 20
Copy 32 bytes from 0x100 to 0x200 overwriting the original data.