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21.2.2.2. Write an Image
SDFI, SDFO–System Data Format I/O Routines
Each call to SDFO$ writes one image to the file or element. The calling program must
supply the image and an ICW for the image. The calling program places the image in the
image buffer and places the ICW in word 10 of the SDFO packet. SDFO combines the
ICW and the image and places them in the I/O buffer to be written out.
SDFO does not actually write an image to the file or element every time SDFO$ is called.
SDFO places the images in the I/O buffer or buffers. When the buffer is filled or a call is
made to SDFOC$ to close SDFO, the buffer is written out to the file or element.
SDFO maintains the write address when writing to a file or element. The calling
program only needs to specify the initial write address.
Calling Sequence for SDFO$
Auto Switch Common Bank or
Relocatable
L,U A0,address-of-packet
LMJ X11,CBSDFO$-1
error return
normal return
L,U A0,address-of-packet
I$BJ X11,CBSDFO$
error return
normal return
Relocatable
L,U A0,address-of-packet
LMJ X11,SDFO$
error return
normal return
If SDFO takes the error return, register A4 contains the error code. See 21.3 for an
explanation of error codes.
If SDFO takes the normal return, the image has been successfully written to the file or
element.
21.2.2.3. Close SDFO
After all images have been written, the calling program must close SDFO by calling the
entry point SDFOC$. SDFO places an end-of-file control record (077 in S1 of the ICW) in
the I/O buffer and writes the buffer out to the file or element. If SDFO is writing to mass
storage, it returns a sector address in word 5. This is the next available address to write
to in the file. If SDFO is writing to tape, an end-of-file mark is written to the tape.
Calling Sequence for SDFOC$
Auto Switch Common Bank or
Relocatable
L,U A0,address-of-packet
LMJ X11,CBSDFOC$-1
error return
normal return
L,U A0,address-of-packet
I$BJ X11,CBSDFOC$
error return
normal return
Relocatable
L,U A0,address-of-packet
LMJ X11,SDFOC$
error return
normal return
7833 1733–004 21–17