DOS Fn 49H: Free Allocated Memory Block

                                                         Compatibility: 2.0+ 
 Expects: AH    49H
          ES    segment address (paragraph) of allocated memory to release
 Returns: AX    error code if CF is set to CY
    Info: Deallocates (frees) the block of memory starting at ES:0000.
          This block will become available for other system resources.

          DOS prevents a process from freeing blocks of memory that were
          allocated by another process (the PID▲ of the owner is saved
          in the MCB).  The undocumented DOS Fn 50H lets you become the
          "current process" and thus free blocks you don't really own.

          It is recommended that a TSR program free its environment block
          during installation (that is, if it won't need it again!).  This
          allows the next program to reuse that block.

See Also: Memory Control Functions
          Memory Control Block
          DOS Functions