UNIVERSITY OF COLOMBO

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UNIVERSITY OF COLOMBO SCHOOL OF
COMPUTING
IT2101 Computer Architecture Operating Systems
DEGREE OF BACHELOR OF INFORMATION TECHNOLOGY
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Agenda
1. Review of RISC 2. Review Memory Access
3. Review Unix Commands
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• Q10. The following are four statements about
  Reduced Instruction Set Computer (RISC)
  architectures.
• (i) The typical RISC machine instruction set is
  small, and is usually a subset of a CISC
  instruction set.
• (ii) No arithmetic or logical instruction can
  refer to the memory directly.
• (iii) A comparatively large number of user
  registers are available.
• (iv) Instructions can be easily decoded through
  hard-wired control units.
• Which of the above statements is/are true?

(a) (i) and (iii) only (b) (i), (iii) and (iv)
only (c ) (i), (ii) and (iii) only (d) (i), (ii)
and (iv) only (e) all are true.
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• RISC Properties in brief
• A simple instruction set ? No complex addressing
  modes
• Constant length instruction
• A large register file
• Hard wired control unit ? no need for micro
  programming

CISC process have almost opposite
characteristics of above.
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• Q10. The following are four statements about
  Reduced Instruction Set Computer (RISC)
  architectures.

(i) The typical RISC machine instruction set is
small, and is usually a subject of a CISC
instruction set. (ii) No arithmetic or logical
instruction can refer to the memory
directly. (iii) A comparatively large number of
user registers are available. (iv) Instructions
can be easily decoded through hard-wired control
units.
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Which of the above statements is/are true?
(a) (i) and (iii) only (b) (i), (iii) and (iv)
only (c ) (i), (ii) and (iii) only (d) (i), (ii)
and (iv) only (e) all are true.
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11. A Reduced Instruction Set Computer (RISC)
architecture differs from a Complex Instruction
Set Computer (CISC) architecture mainly in
relation to

• (a) the large number of general purpose registers
  of RISC.
• (b) all arithmetic/logic instructions which are
  register based in RISC.
• (c) complex addressing modes which are not
  allowed in RISC.
• (d) RISC CPUs which cannot be driven by slower
  clocks.
• (e) typical RISC machine instructions which are
  variable in length.

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• Q24. In a two level memory hierarchy, the access
  time of the cache memory is 12 nano-seconds and
  the access time of the main memory is 1.5
  micro-seconds. The hit ratio is 0.98. What is
  the average access time of the two level memory
  system?
• 13.5 nsec
• 42 nsec
• 756 nsec
• 41.76 nsec
• 30.24 nsec

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For a two level memory system. tavg hctc
(1- hc) (tc tm) tc - Cache access time tm
- Main memory access time hc - hit ratio
tavg 0.9812 0.02(121500) 42 nsec
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• Q24. In a two level memory hierarchy, the access
  time of the cache memory is 12 nano-seconds and
  the access time of the main memory is 1.5
  micro-seconds. The hit ratio is 0.98. What is
  the average access time of the two level memory
  system?
• 13.5 nsec
• 42 nsec
• 756 nsec
• 41.76 nsec
• 30.24 nsec

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Q.25 The memory system of a certain computer
consists of a hard disk with an access time of 3
milliseconds and a main memory with an access
time of 1.5 microseconds. The hit ratio is 0.85.
What is the average access time of the memory
system?

• (a) 0.851.5 0.153103 microseconds.
• (b) 0.851.5 0.15(3103 1.5)microseconds.
• (c) 0.151.5 0.85(3103 1.5) microseconds.
• (d) 0.151.5 0.851.5 microseconds.
• (e) 0.851.5 0.15(31.5) microseconds.

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Average access time of the memory system tavg
hmtm (1- hm) (th tm) tm - Main memory
access time th - Hard disk access time hm
- hit ratio
tavg 0.851.5 0.15(3103 1.5)
microseconds
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Q.25 The memory system of a certain computer
consists of a hard disk with an access time of 3
milliseconds and a main memory with an access
time of 1.5 microseconds. The hit ratio is 0.85.
What is the average access time of the memory
system?

• (a) 0.851.5 0.153103 microseconds.
• (b) 0.851.5 0.15(3103 1.5)microseconds.
• (c) 0.151.5 0.85(3103 1.5) microseconds.
• (d) 0.151.5 0.851.5 microseconds.
• (e) 0.851.5 0.15(31.5) microseconds.

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• Q39. Consider the following sample directory
  listing of a UNIX file system.
• drwxr-xr-x 2 kamal wheel 512 Jun
  27 1235 robot
• -rw-r- - r - - 1 kamal wheel 551596 Sept
  30 set_bk2.zip
• drwxrwxr-x 2 kamal wheel 512 Mar 20 1427
  sida
• -rwx - - - - - - 1 kamal wheel 4287659 Jun
  27 1236 a.out
• drwxrwxr-x 13 kamal wheel 3584 Apr
  24 2301 ssh
• Which of the following statements is/are true?
• All users of the system can read and modify the
  set_bk2.zip file
• All users of the system can read but not modify
  the set_bk2.zip file
• a.out is a program file, that can be executed by
  all users of the system
• a.out is a program file, that can be executed by
  only its owner
• All users under the wheel group can access and
  create a file under the ssh directory

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UNIX Commands - ls

• ls is used to list the files contained within a
  directory.
• ls lists the contents of the current working
  directory.
• For example
• ls
• testfile1.txt testdir1 testfile2.txt
• shows that there are three files in the current
  working directory.
• does not show which are files, which are
  subdirectories and which are links.
• To get this information a long listing (ls -l) is
  required

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UNIX ls command

• For example
• ls l
• -rw-r--r-- 1 kamal staff 216 March 20
  2230 testfile1.txt
• drwxr-xr-x 2 ajith staff 512 Jan 20 1342
  testdir1
• -rw-r--r-- 1 kamal staff 4523 Mar 22 1720
  testfile2.txt
• The first character in each line indicates if the
  file is a simple file or a subdirectory. A d
  indicates a subdirectory and a (dash) indicates
  a file.
• From the above, testdir1 is a directory and the
  other two files testfile1.txt and testfile2.txt
  are simple files.

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UNIX ls command

• -rw-r--r-- 1 kamal staff 216 March 20
  2230 testfile1.txt
• drwxr-xr-x 2 ajith staff 512 Jan 20 1342
  testdir1
• -rw-r--r-- 1 kamal staff 4523 Mar 22
  1720 testfile2.txt
• Each group of three permissions is r for read, w
  for write and x for execute. The permissions can
  be changed by using the chmod UNIX command.
• File testfile1.txt in the above example has
  owner (kamal) permissions set to read and write
  has group (staff) permissions set to read and has
  world/others permissions set to read.

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UNIX ls command

• -rw-r--r-- 1 kamal staff 216 March 20
  2230 testfile1.txt
• drwxr-xr-x 2 ajith staff 512 Jan 20 1342
  testdir1
• -rw-r--r-- 1 kamal staff 4523 Mar 22
  1720 testfile2.txt
• Each group of three permissions is r for read, w
  for write and x for execute. The permissions can
  be changed by using the chmod UNIX command.
• directory testdir1 in the above example has owner
  (ajith) permissions set to read, write and
  execute has group (staff) permissions set to
  read and execute and has world/others permissions
  set to read and execute.
• The next information given is the number of links
  to a file.

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UNIX ls command

• -rw-r--r-- 1 kamal staff 216 March 20
  2230 testfile1.txt
• drwxr-xr-x 2 ajith staff 512 Jan 20 1342
  testdir1
• -rw-r--r-- 1 kamal staff 4523 Mar 22
  1720 testfile2.txt
• The next information given is the number of links
  to a file.
• The following column shows the owner of the
  file, for example testfile1.txt is owned by
  kamal this is followed by the group name (staff)

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UNIX ls command

• -rw-r--r-- 1 kamal staff 216 March 20
  2230 testfile1.txt
• drwxr-xr-x 2 ajith staff 512 Jan 20
  1342 testdir1
• -rw-r--r-- 1 kamal staff 4523 Mar 22
  1720 testfile2.txt
• The following column gives the size of the file
  in typically in blocks.
• file testfile1.txt has 216 blocks.
• The next column gives the data and time when the
  file was created, or the data and time when the
  file was last changed.
• For example the file testfile1.txt was created,
  or last changed, on March 20 at 2230. The last
  column gives the name of the file.

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UNIX ls command

• -rw-r--r-- 1 kamal staff 216 March 20
  2230 testfile1.txt
• drwxr-xr-x 2 ajith staff 512 Jan 20
  1342 testdir1
• -rw-r--r-- 1 kamal staff 4523 Mar 22
  1720 testfile2.txt
• The following column gives the size of the file
  in typically in blocks.
• file testfile1.txt has 216 blocks.
• The next column gives the data and time when the
  file was created, or the data and time when the
  file was last changed.
• For example the file testfile1.txt was created,
  or last changed, on March 20 at 2230. The last
  column gives the name of the file.

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UNIX ls command

• ls l a.out
• Mode links user group size d/t last
  modified file name
• -wr-rr-- 1 joe staff 6325 Apr 18
  a.out
• - w r - r - - r- -

- (dash) indicates a plain file. File owner
(joe) has read and write permission. Group
members (staff) and others have only read
permission
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• Q39. Consider the following sample directory
  listing of a UNIX file system.
• drwxr-xr-x 2 kamal wheel 512 Jun
  27 1235 robot
• -rw-r- - r - - 1 kamal wheel 551596 Sept 30
  set_bk2.zip
• drwxrwxr-x 2 kamal wheel 512 Mar 20 1427
  sida
• -rwx - - - - - - 1 kamal wheel 4287659 Jun
  27 1236 a.out
• drwxrwxr-x 13 kamal wheel 3584 Apr
  24 2301 ssh
• Which of the following statements is/are true?
• All users of the system can read and modify the
  set_bk2.zip file
• All users of the system can read but not modify
  the set_bk2.zip file
• a.out is a program file, that can be executed by
  all users of the system
• a.out is a program file, that can be executed by
  only its owner
• All users under the wheel group can access and
  create a file under the ssh directory

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• Q41. You are given that the following set of
  UNIX commands is issued.
• ps gt file_1
• ls l gt file_2
• grep secret file_2 gt file_3
• Which of the following can be observed after the
  issue?
• file_2 contains the current directory list and a
  list of current processes
• Each line of file_3 if that file exists, contains
  the word secret
• file_1 contains a list of current processes
• file_2 contains a current directory listing
• file_3 contains a current directory listing with
  the word secret attached.

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UNIX ps command

• The ps command reports information about active
  processes. If no options are specified, you will
  see information about only those processes
  connected to your current terminal session.
• Useful options
• ps -e
• shows information about all processes currently
  running on the system.
• ps -l
• shows, among other things, the priority of your
  job, the memory size in blocks of your process,
  and the cumulative CPU time of the process.

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UNIX grep command

• The grep command allows you to search for a
  specified pattern in one or more files, printing
  any lines which contain the specified pattern.
• grep has the following format
• grep pattern file(s)
• Useful options
• grep -i pattern file
• prints all lines of file that contain the
  pattern, regardless of case.
• For example,
• grep -i cg data
• prints any line of data that contains "cg," "Cg,"
  "cG," or "CG." The -i option ignores the case of
  the string when searching.

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• Q41. You are given that the following set of
  UNIX commands is issued.
• ps gt file_1
• ls l gt file_2
• grep secret file_2 gt file_3
• Which of the following can be observed after the
  issue?
• file_2 contains the current directory list and a
  list of current processes
• Each line of file_3 if that file exists, contains
  the word secret
• file_1 contains a list of current processes
• file_2 contains a current directory listing
• file_3 contains a current directory listing with
  the word secret attached.

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Contact

• External Degree Unit (EDU) of the University of
  Colombo School of Computing
• No. 221/2A, Dharmapala Mawatha,
• Colombo 7.
• Phone [phone]
• Fax [phone]
• http//www.bit. lk

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Thank you