The Allocate Virtual Memory routine allocates a specified number
    of contiguous bytes in the program region and returns the 32-bit
    virtual address of the first byte allocated.

    Format

      LIB$GET_VM  number-of-bytes, base-address [,zone-id]

1  –  Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

2  –  Arguments

 number-of-bytes

    OpenVMS usage:longword_signed
    type:         longword integer (signed)
    access:       read only
    mechanism:    by reference

    Number of contiguous bytes that LIB$GET_VM allocates. The number-
    of-bytes argument is the address of a longword integer containing
    the number of bytes. LIB$GET_VM allocates enough memory to
    satisfy the request. Your program should not reference an address
    before the first byte address allocated (base-address) or beyond
    the last byte allocated (base-address + number-of-bytes-1) since
    that space may be assigned to another routine. The value of
    number-of-bytes must be greater than zero.

 base-address

    OpenVMS usage:address
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference

    First virtual address of the contiguous block of bytes allocated
    by LIB$GET_VM. The base-address argument is the address of an
    unsigned longword containing this base address.

 zone-id

    OpenVMS usage:identifier
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference

    The zone-id argument is the address of a longword that contains a
    zone identifier created by a previous call to LIB$CREATE_VM_ZONE
    or LIB$CREATE_USER_VM_ZONE. This argument is optional. If zone-id
    is omitted or if the longword contains the value 0, the 32-bit
    default zone is used.