skip to main content
article
Free Access

The structure of microcomputer file systems

Published:01 March 1986Publication History
Skip Abstract Section

Abstract

With an understanding of the structure of microcomputer file systems and what causes incompatibilities between them, it is possible to write software that will enable one system to read files written by another—provided they have physically compatible hardware.

References

  1. 1 Digital Research. CP/M 2.0 Interfacr Guide. Digital Research, Pacific Grove, Calif. 1979.Google ScholarGoogle Scholar
  2. 2 Heath Co. He&l! Dfsk Operafir~g S!jstenr Software Rt+re,rct~ Manual. Heath Co. Benion Harbor. Mich. 1980.Google ScholarGoogle Scholar
  3. 3 Morgan. C. and Sufrin. 13. Specifications of the UNIX filing system. IEEE Tram. Softm. Eng. SE-IO, 2 (Mar. 1984). 128-142.Google ScholarGoogle ScholarDigital LibraryDigital Library
  4. 4 Pelowitz. D.G. The HDOS directory structure. REMark 45 (Oct. 1983). 74-77.Google ScholarGoogle Scholar
  5. 5 Pelowitz, DC. The CP/M directory structure. REMark 46 (Nov. 1983). 31-33.Google ScholarGoogle Scholar
  6. 6 Ritchie. D.hl. and Thompson, K. The UNIX time-sharing system. Bell Syst Tech. \. 10, 2 (Jniy-Aug. 1978). 1905-1929.Google ScholarGoogle Scholar
  7. 7 Thompson, K. UNIX implementation. Bell Sysl. Tech. /. IO. 2 (July- Aug. 1978). 193l-1946.Google ScholarGoogle Scholar
  8. 8 Thompson. L.E. Floppy-disk formats. Byte 9. 10 (Sept. 1984). 147.Google ScholarGoogle Scholar

Index Terms

  1. The structure of microcomputer file systems

              Recommendations

              Reviews

              Paul W. Abrahams

              This paper describes how files are organized on diskettes by microcomputer operating systems and considers the problem of reading files that were written on a diskette by a system other than the host system. It presumes that the diskette formats for the host system and the foreign system are at least physically compatible—that is, the host system can locate and read any disk sector written by the foreign system. It describes disk directories, data pointers that chain through the data of a file, and allocation tables in general. It also discusses specifically the file organizations used by three operating systems: CPM, PC-DOS, and HDOS (the Heath/Zenith operating system). All of these operating systems use diskette formats physically compatible with the IBM PC hardware. The paper suggests that the way to read a diskette written on a foreign system is to construct an allocation table on the host system in a standard format, but then never really follows through on this suggestion. The information proposed for this allocation table seems redundant: It includes both the length of each file segment and the offset of that segment from the start of the file, even though the offset can always be computed as the sum of the previous lengths. Furthermore, the paper does not address at all the question of where the allocation table should be stored. There is no room for it on the diskette itself; but if it is stored in memory, it needs to be reconstructed each time the diskette is changed. In practice, the best way to deal with a diskette from a foreign system is to read it once and copy its files to a host-format diskette, thus removing any need for an allocation table of the sort discussed in this paper. I found this paper disappointing and unfocused. The discussions of specific operating systems are not very interesting for readers who don't have to deal with those particular systems, and not detailed enough for those readers who do. At the same time, the general methods proposed don't seem appropriate to the task. The topic of microcomputer file systems is an interesting and important one, but this paper does not do justice to it.

              Access critical reviews of Computing literature here

              Become a reviewer for Computing Reviews.

              Comments

              Login options

              Check if you have access through your login credentials or your institution to get full access on this article.

              Sign in

              Full Access

              • Published in

                cover image Communications of the ACM
                Communications of the ACM  Volume 29, Issue 3
                The MIT Press scientific computation series
                March 1986
                71 pages
                ISSN:0001-0782
                EISSN:1557-7317
                DOI:10.1145/5666
                Issue’s Table of Contents

                Copyright © 1986 ACM

                Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from [email protected]

                Publisher

                Association for Computing Machinery

                New York, NY, United States

                Publication History

                • Published: 1 March 1986

                Permissions

                Request permissions about this article.

                Request Permissions

                Check for updates

                Qualifiers

                • article

              PDF Format

              View or Download as a PDF file.

              PDF

              eReader

              View online with eReader.

              eReader