Reference Guide

74 Chapter 4

Assembler Directives and Pseudo-Operations

.COMM Directive

The .COMM directive makes a storage request for a speciﬁed number of

bytes.

Syntax

label .COMM [ num_bytes]

Parameters

label Labels the location of the reserved storage.

num_bytes An integer value for the number of bytes you want to

reserve. The Assembler uses a default value of 4 if the

.COMM directive lacks a num_bytes parameter.

Permissible values range from one to 0x3FFFFFFF.

Discussion

The .COMM directive declares a block of storage that can be thought of as

a common block. You must label every .COMM directive. The linker

associates the label with the subspace in which the .COMM directive is

declared and allocates the necessary storage within that subspace.

.COMM always allocates its space in the $BSS$ subspace of the

$PRIVATE$ space. If the label of a .COMM directive appears in several

object modules, the linker uses the maximum size speciﬁed in any

module when it allocates the necessary storage in the current subspace.

Example

This example reserves 16 bytes of storage for mydata.

.BSS

mydata .COMM 16