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GOALS
To study
To study the basic principles
of I/O and buffering.
To get familiar with directory
and file management and the duties of
the OS when a process uses files.
To be able to describe the differences
between processes and threads and their usage in the systems.
Key words: I/O methods, device dependent and device independent I/O, file management, disk management, threads
TEXT IN COURSE BOOK
- Stallings ch. 11.1-11.4:
I/O Management
- 5.ed: pages 158-172
- 4.ed: pages 154-168
- Stallings ch. 12.1-12.7:
File Management
- 5.ed: pages 480-493
- 4.ed: pages 474-486
- Stallings ch. 4.1:
Threads.
- 5.ed: pages 536-570
- 4.ed: pages 526-554
SLIDES and OTHER MATERIALS
- Slides in Finnish are available from the course page
- Luento 8: I/0 2s/A4, 6s/A4
- Luento 9: File system - part 1 2s/A4, 6s/A4
- Luento 10: File Systems - part 2 2s/A4, 6s/A4
- Luento 11: Threads 2s/A4, 6s/A4
- Luento 12: Operating system development and features 2s/A4, 6s/A4
- Official book site: See also Stallings's pages If you need to have English slides that are based on this book. You can find them from the 'instructor resourses' link. Please notice that they cover the whole book, while our course only covers certain parts.
Other Materials: Tanenbaum A.S.: Modern Operating Systems. 2nd ed. 2001. Pages 81-94,269-300, 399-408, 445-448.
STUDY TEAMS
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Before the first meeting: Study the following team task carefully. Think about possible solutions. Write down all your ideas, results, problems, and unclear parts. 1. meeting: In a study group, study the task together. Think and discuss about what issues you already know, what items you need to find more information about, what information is needed, etc. You can consult the teacher of the small group session, but he will not solve the problems for you. He can gie you hints and show the right way for solveing the problem, if you are totally lost. Between the two meetings: You may need to discuss together between the meetings to write your report. These discussion you need to organise yourselves. You may wish to use personal meetings at Exactum or somewhere else, use e-mail, irc, webCT (if you want to use webCT, please contact Tiina Niklander). You are expected to write your report before the second meeting. 2. meeting: Study groups present their solutions and report contents to other groups during the meeting. After the 2. meeting: If you feel that you need to modify your report, you'll have until Monday after the meeting to finalise your report. For example, you may want to add/change/correct some items in your report based on the presentations during the meeting. |
The report (containing part A-C) must be returned on paper latest on Monday 17.10. into the mailbox beside the room D225 (before 12 o'clock). You can also leave the report to the teacher during the small group meeting on Wednesday 12.10.
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This time the process needs to access file JEMMA. Actually the process wants to read only one byte from the file. However, it does not want to read the first byte, but 2152nd byte. Please describe in your report, using the detail level of the course book, all the features and parts of operating system, hardware and file sytems, which particiapte in fulfilling the processes task. Describe also what happens in the system, when it servers the process's request. The process may open and close the file implicitly or explicitly. You must chose one model and justify your selection. Explicit file opening means that the process must before accessing the file open the file using a spcific system call. When the system uses implicit file opening, the operating system opens the file when process makes first access to it. For this the process can use using any available system call. Please remember also to explain the directory structure you use. Describe how it is used in the file opening and maintaining the access control information. The file JEMMA is stored on a file system that uses File Allocation Table (FAT). A FAT file system considers the disk to be a queue of continuously numbered blocks. The numbering starts from the outermost track. First you number all the sectors in the outermost track and then continue the numbering track by track numbering all sectors in each track. This block numer can be though as the index to a one-dimensional array, where the elements are the blocks. The specific disk, where the file JEMMA is located, has two surfaces (numbered as 0 and 1). Both surfaces have 80 tracks (numbered from 0 to 79.) Track 0 is the outermost track. Each track is divided to 18 sectors (numbers 1 to 18). The size of one sector and one block is the same, 512 bytes. The first sector is reserved for the Master Boot Record, 18 sectors have been reserved for the file allocation table including its backup, and 14 sectors for the root directory. These sectors are all reserved from the beginning of the disk. The file allocation is done using chained allocation. The directory contains the file name, file attributes and the number of the file's first block. All the other block can be found from the file allocation table folowing the links stored there. The first block of File JEMMA is block number 44, and the content of the file allocation table is: 43: 44: 45 45: 46 46: 50 47: 48: 49: 50: 51 51: 52 52: 60 During your explanation make sure that you also explain where (surface, track, sector) the byte 2152 can be found. Take extra care to explain how this information travels between the operating system and the disk itself. As an additional discussion you could concider what happens in a FAT file system, if the Free Block List or BitTable is lost due to some failure? Can the disk still be used safely, what can be done to recover the list? Is it still safe to read or write on the disk?
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Each team: List five review questions that you consider most relevant for this section, and explain why it is important to understand the answers. A good review question requires understandin a lot about the issue. A question that only asks about some very small details is not a very good review question. If there are areas that would need more detailed explanations, please give a hint. |
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Each team: Please evaluate your teams work as well as your own work using the following pdf form . The form will be handed to the team in the small group session. The evaluation has two goals: (1) to collect information about the exercises and study groups, and (2) to help study groups to make their work even better. We appriciate short answers that give the essentials in a compact form. Please try to be open minded. Answer to each question and give also your reasonings. |
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