DMS DMS DMS RDC PUN
PRT I - 1"""- I , I I I I Channel DMSCIO DMSPID - -+ SIO / DMSIOW I -- -
- I- I I - I I -.,.. - -- I I Figure 18. Flow of Control for Unit Record I/O processing DMSITI I The following are more detailed descriptions of the flow of control for
the read, punch, and print unit record control functions. Initializes block length and unit record size. Initializes areas to read records. Issues an 510 command to read a record. Sets the wait
old PSi from NUCON. read I/O is complete.
bit for the virtual card reader and load the I/O This causes CMS to enter a wait state until the DMSITI: Ensures that this interrupt is for the virtual reader. If not, the--I/O old PSi is loaded, returning CftS to a wait state. If the
interrupt is for the reader, DKSITI resets the wait bit in the I/O old PSi and loads it, causing control to return to Places the symbolic name of the interrupting device in the PLIST and passes control to the calling routine. ChecKs for SENSE information
necessary.
and handle I/O errors, if CMS Method of Operation and Program Organization 2-95

Displays a control record at the console. If another control record is encountered, formats it via D!SSCN. Displays the new control record at the console. Closes the file when end-of-file occurs. Issues a CP CLOSE command to close the card reader. DMSPUN: Ensures that a virtual punch is available; processes PUNCH coiiand options. DMSSTT: Verifies the existence of the file and returns its starting address. If requested, sets up a header record and calls DMSCiR to write it to the console. DMSBRD: Reads a block of data into the read buffer; continues reading untiY-the buffer is filled. Initializes areas to punch records. Issues the SIO instruction to punch the contents of the buffer. Issues a call to DMSIOW to wait for completion of the punch I/O operation. Sets the wait bit on for the virtual punch device and loads the I/O old PSi from NUCOI. This causes CMS to enter a wait state until the
punch operation completes. QMSI!!: Ensures that this interrupt is for the punch. If not, the I/O old PSi is loaded returning CMS to a wait state. If the interrupt is for
the punch, DMSITI resets the wait bit in the I/O old PSW and then loads
the PSi, returning control to DMSIOW. DMSIOW: Places the symbolic name of the interrupting device in the PLIST and passes control to DMSCIO. Checks for SENSE information and handles I/O errors, if any. Handles error returns and resets constants for the next punch
operation. Closes the file and returns control to the co.mand handler, DMSINT. 2 Determines the device type of the printer. Checks out the specified fileid. Checks out the options specified on the PRINT command line. DMSSCN: Verifies the existence of the file and returns its starting address. 2-96 IBM VM/310 System Logic and Program Determination--Volume 2