can you answer 8a and 8b Assume you have a magnetic hard disk with tracks number

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can you answer 8a and 8b

Assume you have a magnetic hard disk with tracks numbered from 0.127, track o being the outermost track. As a simplifying assumption, assume tracks have 64 sectors 0-63. Given the list of read requests to specific sectors listed below, show the order in which the scheduling. Use the following assumptions: Given a sector, S, another sector in the same track as s will be closer (and therefore have a shorter seek time) than a sector in a different track. Seek time is directly proportional to the difference between track numbers. For example, moving from track 1 to track 2 would take half as long as moving from track 5 to track 7. Multiple sectors in the same track will be read in ascending order (lowest number first). The sequence should always start with the first request in the list (track 40, sector 5) Once that request has been serviced, all other requests can be serviced in any order. Request list: i. Track 40, sector 5 ii. Track 15, sector 60 iii. Track 100, sector 0 iv. Track 95, sector 12 v. Track 40, sector 63 vi. Track 0, sector 0 vii Track 15, sector 59 viii. Track 127, sector 63 a. Operating systems often contain direct support for one specific file type but otherwise require applications to impose other types based on file structure. What one type must the operating system support, and why? b. A file created on a Unix system should be readable to public, readable and the executable to its and readable, writeable, and executable to its owner. What 3-dagit integer represents the access rights for this file? Briefly explain your answer.

Explanation / Answer

8 a) The OS normally provides direct support for system file types.
- System file types are distinguished from normal file types in a way that they their existence helps in normal system functioning. Common extensions being .DLL, .DRV, .SYS, and .CAB.
- Without the help of these important system files, any OS would be redundant to perform any OS related functions namely important ones like-
Memory Management
Processor Management
Device Management
File Management
- Because of criticality of the system files in normal functioning of the OS, they are normally hidden are are read-only.

8 b) It needs to be understood that file permission in unix are imposed on 3 levels: owner,group and public level.
- Each level has 3 permissions: rwx (read-write-execute) with assigned digits (4-2-1) i.e. numbers are assigned with 2 to the power of the locations from right to left at a particular level.
- A file having following permission means:
   -rwxrwxr--
   Skipping the left most significant bit, which is marked with an underscore is the special permission flag whose meaning can vary.

   The next 3 digits encountered are rwx: which is permissions imposed on the owner level, it translates in number as (421) i.e. 7.
   The next 3 digits encountered are rwx: which is permissions imposed on the group level, it translates in number as (421) i.e. 7.
   The next 3 digits encountered are r--: which is permissions imposed on the other level, it translates in number as (4--) i.e. 4.

   So the combined file permission is 774.

- So keeping this in mind, we can see that the information given in the question translates to the following:
file should be readable, writeable and executable to the owner. 421=7
file should be readable and executable to the group. 4_1=5
file should be only readable to the public. 4__=4

so the 3 digit file rights of this file is 754.

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