Open the file in hexl-mode.
M-x hexl-find-file
Or you can open the file and enter hexl-mode.
M-x hexl-mode
Exit hexl-mode.
M-x hexl-mode-exit
Insert a byte with a code typed in hex.
C-M-x <hex>
Open the file in hexl-mode.
M-x hexl-find-file
Or you can open the file and enter hexl-mode.
M-x hexl-mode
Exit hexl-mode.
M-x hexl-mode-exit
Insert a byte with a code typed in hex.
C-M-x <hex>