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*                                                                     *         
* Module name: BLOCKTAP                                               *         
*                                                                     *         
* Syntax: BLOCKTAP ON|OFF|Q|CLOSE <(<TAPN|CCU> <BLOCK|NOBLOCK> SILENCE          
*                            <TYPE|NOTYPE>  <)>>               SILENCE          
*                                                                     *         
*                                                                     *         
* Default Options: TAP1 BLOCK TYPE                             SILENCE          
*                                                                     *         
* Purpose: Trap TAPEIO calls and change the blocksize to 32k (approx) *         
*          This was written expressly to improve the functions of     *         
*          VMFPLC2 and TAPE. There are sequences of I/O operations    *         
*          which are probably NOT handled correctly by this routine   *         
*          but it should work correctly for all sequences generated   *         
*          by VMFPLC2 and TAPE.                                       *         
*                                                                     *         
*          Tapes created withOUT BLOCKTAP will be readable with       *         
*          BLOCKTAP ON.                                               *         
*                                                                     *         
* Author: Steven C. Howes   Brigham Young University                  *         
*                                                                     *         
* Version: 1                                                          *         
*                                                                     *         
* Date: 11 May 1987                                                   *         
*                                                                     *         
* BLOCKTAP ON installs the nucleus extension (unless already          *         
* installed) and turns it ON for the specified (or defaulted) device. *         
*                                                                     *         
* BLOCKTAP OFF turns it OFF for the specified (or defaulted) device   *         
* and removes the nucleus extension if no devices are still ON. It    *         
* performs the CLOSE and Q functions before extracting itself.        *         
*                                                                     *         
* BLOCKTAP CLOSE performs any necessary tape operations to insure     *         
* that the physical tape reflects the commands which have been        *         
* buffered. The buffer is empty after this operation. It performs the *         
* Q function after closing.                                           *         
*                                                                     *         
* BLOCKTAP Q gives statistics for output operations. Included are the *         
* number of bytes, gaps and tape marks written. Also, the length of   *         
* tape written in feet. (Both virtual (what would have been written   *         
* withOUT BLOCKTAP) and real (what was actually written to the tape)  *         
* are reported.                                                       *         
*                                                                     *         
* Option NOBLOCK specifies that the output tape blocksize is NOT to   *         
* be altered. This option will optimize tape movement and eliminate   *         
* the extra gaps produced by superfluous tape marks and subsequent    *         
* re-positioning of the tape.  Tapes created with this option will    *         
* be readable withOUT BLOCKTAP.                                       *         
*                                                                     *         
* Options BLOCK and NOBLOCK may be specified ONLY with the ON         *         
* function.                                                           *         
*                                                                     *         
* Option TYPE specifies that statistics are to be given on the SILENCE          
* CLOSE and OFF functions.                                     SILENCE          
*                                                              SILENCE          
* Option NOTYPE specifies that statistics are NOT to be given  SILENCE          
* on the CLOSE and OFF functions. The confirmation messages on SILENCE          
* the ON function are also suppressed. This option has NO      SILENCE          
* effect on the Q function.                                    SILENCE          
*                                                              SILENCE          
* The TYPE/NOTYPE setting is preserved for the specified       SILENCE          
* device until changed (by specifying the opposite setting).   SILENCE          
*                                                              SILENCE          
* NO warrantee of ANY kind is either expressed or implied             *         
* by the author  or Brigham Young University.                         *         
*                                                                     *         
* This command installs a Nucleus Extension for the TAPEIO function.  *         
* The nucleus extension buffers I/O requests and causes the tape to   *         
* be written in standard OS VariableBlocked format. Each record in    *         
* this format is one TAPEIO request. A block is written to tape ONLY  *         
* when addition of data to it would cause it to exceed 32760 bytes.   *         
* It is also written if an ERG, SENSE, REW or RUN command is given.   *         
*                                                                     *         
* Note that WTM, BSF, FSR and BSR commands are buffered. This saves   *         
* tape when the "standard" CMS command sequence of "write the file,   *         
* WTM, WTM, BSF, BSF" is issued over and over again... 'cause the     *         
* superfluous tape marks are NOT written.                             *         
*                                                                     *         
* The user must NOT re-position the tape with any CP commands while   *         
* BLOCKTAP is ON 'cause the last few commands are probably still in   *         
* the buffer and were NOT written to the tape!!!                      *         
*                                                                     *         
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