Specifying a File Code

MPE/iX subsystems often create special-purpose files whose functions are identified by four-digit integers called file codes, written in their system file labels. HPFOPEN/FOPEN, BUILD, and FILE have parameters that enable you to specify a file code for your file when you first create it. For user files, you can use as a file code any number from 0 through 1023. Numbers above 1023 listed in Table 2-7 “Reserved File Codes” are predefined by Hewlett-Packard for special system files and should not be redefined for your use. If you do not specify a file code when you create a file, the MPE/iX default value of zero applies.

For instance, compilers create Native Mode Object (NMOBJ) files, written in a special format and identified by the code 1461, upon which they compile object programs. User programs sometimes create files that must be identified in some unique way, too. Such a program might produce a permanent disk file identified by the integer 1. If you were to run this program several times and want to uniquely identify the file produced on each run (or set of runs) by a special class, purpose, or function, you could use a FILE command to supply a unique file code for each run (or group of runs).

For instance, on the second run, you might wish to classify the file with the file code 2, as follows:

                         File code 

                         |

   FILE DESGX=DESGB;CODE=2

   RUN FILEPROD

If you later wished to determine the classification to which this file belonged, you could use the LISTFILE command with an information level of 1, which prints the file name, file code, and other information about the file. Alternatively, you could determine the file code by calling the FFILEINFO intrinsic. Both LISTFILE and FFILEINFO are discussed in Getting System Information Programmer's Guide (32650-90018). The file codes that have particular Hewlett-Packard-defined meanings are listed in Table 2-7 “Reserved File Codes”.

	NOTE: Default is the unreserved file code of 0.

Using 1090 (LOG) as a designated file code may not yield the number of records that you specify in the DISC= parameter. Most files use the number of records specified in the DISC= parameter as the maximum limit; user logging uses this specified number as a minimum.