The Erase Characters routine erases characters in a virtual
    display by replacing them with blanks.

    Format

      SMG$ERASE_CHARS  display-id ,number-of-characters ,start-row

                       ,start-column

1  –  Returns

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

2  –  Arguments

 display-id

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

    Specifies the virtual display from which characters will be
    erased. The display-id argument is the address of an unsigned
    longword that contains the display identifier.

    The display identifier is returned by SMG$CREATE_VIRTUAL_DISPLAY.

 number-of-characters

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

    Specifies the number of characters to be replaced with blanks.
    The number-of-characters argument is the address of a signed
    longword that contains the number of characters to be replaced
    with blanks.

 start-row

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

    Specifies the row on which the erase operation begins. The start-
    row argument is the address of a signed longword that contains
    the number of the row at which the erasure is to begin.

 start-column

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

    Specifies the column on which the erase operation begins. The
    start-column argument is the address of a signed longword that
    contains the number of the column at which the erasure is to
    begin.