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### 4.5 bss Section

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.

The `.lcomm` pseudo-op defines a symbol in the bss section; see `.lcomm`.

The `.comm` pseudo-op may be used to declare a common symbol, which is another form of uninitialized symbol; see See `.comm`.

When assembling for a target which supports multiple sections, such as ELF or COFF, you may switch into the `.bss` section and define symbols as usual; see `.section`. You may only assemble zero values into the section. Typically the section will only contain symbol definitions and `.skip` directives (see `.skip`).