;$IO    WAIT    WAIT ON I/O COMPLETE
;.      13-SEPT-76  P. CANNON
;.
;.      THIS MODULE GIVES THE FORTRAN PROGRAMMER THE OPTION
;.      OF OVERLAPPING I/O AND COMPUTATION. ALL I/O ROUTINES
;.      STARTING WITH I ONLY INITIATE AN I/O OPERATION AND
;.      THE USER MUST CHECK ON I/O COMPLETION USING WAIT.
;.
;.      CALL WAIT(FDB,/NBT/,/IER/)
;.
;.      FDB     FILE DESCRIPTOR BLOCK
;.      NBT     OPTIONAL PARAMETER CONTAINING THE NUMBER OF BYTES
;.              TRANSFERRED
;.      IER     ERROR FLAG
;.              POSITIVE IMPLIES NO ERROR
;.              ZERO IMPLIES END OF FILE
;.              NEGATIVE IMPLIES HARDWARE I/O ERROR
;.
;       THE GENERAL FORM OF THE WAIT$ MACRO IS :
;       WAIT$   FDB,BKEF,BKST,ERR
;
;       WHERE:
;       FDB     ADDRESS OF THE FILE DESCRIPTOR BLOCK
;       BKEF    A NUMERIC VALUE SPECIFYING THE EVENT FLAG NUMBER
;               TO BE USED FOR SYNCHRONIZING BLOCK I/O OPERATIONS.
;       BKST    ADDRESS OF A 2-WORD I/O STATUS BLOCK IN THE USER
;               PROGRAM.
;       ERR     THE SYMBOLIC ADDRESS OF AN OPTIONAL USER-CODED
;               ERROR-HANDLING ROUTINE.
;
        .TITLE  WAIT - WAIT ON I/O COMPLETE
        .IDENT  /V01/
       .PSECT
        .GLOBL  WAIT
        .GLOBL  BIOCMP
        .MCALL  WAIT$
EF:     .WORD   0               ;ADDRESS OF PARAMETER LIST
        .WORD   0               ;NBR OF TIMES CALLED
WAIT:   MOV     R5,EF           ;SAVE ADDRESS OF PARAMETER LIST
        INC     EF+2            ;ADD ONE TO THE NBR OF TIMES CALLED
        MOV     (R5)+,R4        ;LOAD THE NUMBER OF PARAMETERS
        MOV     (R5)+,R0        ;LOAD THE ADDRESS OF THE FDB
        DEC     R4              ;COMPUTE THE NBR OF OPTIONAL PARAMETERS
        JSR     PC,BIOCMP       ;WAIT ON I/O TO COMPLETE,UPDATE THE
                                ;OPTIONAL PARAMETERS
        RTS     PC
        .END