The bss section is used for local common variable storage. You may allocate address space in the bss section, but you may not dictate data to load into it before your program executes. When your program starts running, all the contents of the bss section are zeroed bytes.
Addresses in the bss section are allocated with special directives; you
may not assemble anything directly into the bss section. Hence there
are no bss subsections. See section .comm symbol , length ,
see section .lcomm symbol , length.