UNIT NAME:  DOS

  DECLARATION:  USES DOS;

      PURPOSE:  DOS Operation, File handling.  ( Not standard to ANSI Pascal )

                          PROCEDURES and FUNCTIONS
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  Interrupt support procedures 

  GetIntVec         Returns the address stored in a specified interrupt
                    vector
  Intr              Executes a specified software interrupt
  MsDos             Executes a DOS function call
  SetIntVec         Sets a specified interrupt vector to a specified
                    address


  Date and Time procedures 

  GetDate           Returns the current date set in the operating system
  GetFTime          Returns the date and time a file was last written
  GetTime           Returns the current time set in the operating system
  PackTime          Converts a DateTime record into a 4-byte, packed
                    Date-and-Time character LongInt used by SetFTime
  SetDate           Sets the current date set in the operating system
  SetFTime          Sets the date and time a file was last written
  SetTime           Sets the current time set in the operating system
  UnpackTime        Converts a 4-byte, packed Date-and-Time character LongInt
                    returned by GetFTime, FindFirst, or FindNext into an
                    unpacked DateTime record


  Disk status functions 

  DiskFree          Returns the number of free bytes on a specified disk
  DiskSize          Returns the total number of bytes on a specified disk


  File handling procedures 

  FindFirst         Searches the specified (or current) directory for the
                    first entry that matches the specified file name and set
                    of attributes
  FindNext          Returns the next entry that matches the name and
                    attributes specified in a previous call to FindFirst
  FSplit            Splits a filename into its three component parts;
                    directory, filename, and extension
  GetFAttr          Returns the attributes of a file
  SetFAttr          Sets the attributes of a file


  File handling functions 

  FExpand           Accepts a file name and returns a fully qualified
                    filename (drive, directory, extension)


  Process handling procedures 

  Execute           Executes a specified program with a specified command line
  Keep              Terminates a program and keeps it in memory; otherwise
                    known as Terminate-and-Stay-Resident (TSR)
  SwapVectors       Swaps all saved interrupt vectors with the current vectors


  Process handling functions 

  DosExitCode       Returns the exit code of a sub-process


  Environment handling functions 

  EnvCount          Returns the number of strings in the DOS environment
  EnvStr            Returns a specified environment string
  GetEnv            Returns the value of a specified environment variable


  Miscellaneous procedures and functions 

  DosVersion        Returns the DOS version number
  GetCBreak         Returns the state of CTRL-Break checking in DOS
  SetCBreak         Sets the state of CTRL-Break checking in DOS
  GetVerify         Returns the state of the verify flag in DOS
  SetVerify         Sets the state of the verify flag in DOS

        (See reference section for details of each procedure/function)