CBSE Previous Year Solved  Papers  Class 12 Computer Science Delhi 2015

Time allowed : 3 hours                                                                                           Maximum Marks: 70

General Instructions :

  1.  There are a total of 26 questions and five sections in the question paper, All questions are compulsory.
  2. Section A contains question number 1 to 5, Very Short Answer type questions of one mark each.
  3.  Section B contains question number 6 to 10, Short Answer type I questions of two marks each.
  4.  Section C contains question number 11 to 22, Short Answer type II questions of three marks each.
  5.  Section D contains question number 23, Value Based Question of four marks.
  6. Section E contains question number 24 to 26, Long Answer type questions of five marks each.
  7. There is no overall choice in the question paper, however, an internal choice is provided in one question of two marks, one question of three marks and all three questions of five marks. An examined is to attempt any one of the questions out of two given in the question paper with the same question number.



Question.1. (a) Name the function/method required to
(i) check if a string contains only upper case letters
(ii) give the total length of the list.
(b) Rewrite the following Code in python after removing all syntax error(s). Underline each correction done in the code.
(c) Find and Write the output of the following python code :
(d) Find and write the output of the following python code :
(e) What are the possible outcome(s) executed from the following code ? Also specify the maximum and minimum values that can be assigned to variable NUMBER.

Question.2. (a) Illustrate the concept of inheritance with the help of a python code.
(b) What will be the output of the following python code ? Explain the try and except used in the code.
(c) Write a class PICTURE in Python with following specifications:
(d) What is operator overloading with methods ? Illustrate with the help of an example using a python code.
(e) Write a method in python to display the elements of list thrice, if it is a number and display the element terminated with ‘#’ if it is not a number.
For example, if the content of fist is as follows :
Answer: (a) Inheritance: Python supports inheritance, it even supports multiple inheritance. Classes can inherit from other classes. A class can inherit attributes and behaviour methods from another class, called the super class. A class which inherits from a super class is called .a subclass, also called heir class or child class. Super classes are sometimes called ancestors as well. There exists a hierarchy relationship between classes, we define a class Calendar Clock, which inherits both from the class Calendar and from the class Clock.
Here try and its except statement form a unit. The scope of the except clause is restricted to those statements specified by the immediately preceding try statement. A except statement cannot catch an exception thrown by another try statement.
(d) Operator overloading is a specific case of polymorphism in which’ some or all operators like +, = or == are treated as polymorphic functions and as such have different behaviours depending on the types of its arguments. here we overload the + sign, in the class Point.

Question.3. (a) What will be the status of the following list after fourth pass of bubble sort and fourth pass of selection sort used for arranging the following elements in descending order ?
14, 10, -12, 9, 15, 35
(b) Write a method in python to Search for a value in a given list (assuming that the elements in list are in ascending order) with the help of Binary Search method. The method sould return -1, if the value not present else it should return position of the value present in the list.
(c) Write PUSH (Books) and POP (Books) methods in python to add Books and remove Books considering them to act as Push and Pop operations of Stack.
(d) Write a method in python to find and display the prime numbers between 2 to N. Pass N as argument to the method.
(e) Evaluate the following post fix notation of expression.
Show status of stack after every operation.
84, 62, -, 14, 3, *, +

Question.4. (a) Differentiate between the following :
(i) f = open (‘diary.txt’, V)
(ii) f = open (‘diary, text’ , ‘w’)
(b) Write a method in python to read the content from a text file diary.txt line by fine and display the same on screen.
(c) Consider the following definition of class Member, write a method in python to write the content in a pickled file member.dat.


Question.5. (a) Observe the following table carefully and write the names of the most appropriate columns, which can be considered as (i) candidate keys and (ii) primary key:
(b) Consider the following DEPT and WORKER tables. Write SQL queries for (i) to (iv) and find outputs for SQL queries (v) to (viii).
Note: DOJ refers to date of joining and DOB refers to date of Birth of workers. in ascending order of Wno.
(ii) To display the Name of all the FEMALE workers from the table WORKER.
(iii) To display the Wno and Name of those workers from the table WORKER who are born between ‘1987 01, 01 and ‘1991-12-01’.
(iv) To count and display MALE workers who have joined after T986-01-01’.

Question.6. (a) Verily the following using Boolean Laws :
X+Y’ = X.Y+X.Y’+ X’.Y‘
(b) Draw the Logic Circuit for the following Boolean Expression :
(U+V>.W + Z
(c) Derive a Canonical SOP expression for a Boolean function F represented by the following truth table.

Question.7. (b) What is a spam mail ?
(c) Differentiate between ftp and http.
(e) What is Worm ? How is it removed ?
(f) Out of the following, which all comes under cyber crime ?
(i) Stealing away a brand new computer from a showroom.
(ii) Getting in someone’s social networking account without his consent and posting pictures on his behalf to harass him.
(iii) Secretly copying files from server of a call center and selling it to the other organization.
(iv) Vewing sites on a internet browser.
(e) Perfect Edu Services Ltd. is an educational organization. – It is planning to set up its India campus at Chennai with its head office at Delhi. The Chennai campus has 4 main buddings – ADMIN, ENGINEERING, BUSINESS and MEDIA.
you as a network expert have to suggest the best network related solutions for their problems raised in (i) to (iv), keeping in mind the distances between the buildings and other given parameters.
(i) Suggest the most appropriate location of the server inside the CHENNAI campus (out of the 4 buildings), to get the best connectivity for maximum number of computers. Justify your answer.
(ii) Suggest and draw the cable layout to efficiently connect various’ buildings within the CHENNAI campus for connecting the computers.
(iii) Which hardware device will you suggest to be procured by the company to be installed to protect and control the internet uses within the campus ?
(iv) Which of the following will you suggest to establish the online face-to-face communication between the people in the Admin Office of CHENNAI campus and DELHI-I Head Office ?
(i) Cable TV
(ii) Email
(iii) Video Conferencing
(iv) Text Chat .
Answer : (b) spam Email, also known as junk email or * unsolicited bulk email (UBE), is a subset of electronic spam involving nearly identical messages sent to numerous
recipients by email. Clicking on links in spam email may send users to phishing web sites or sites that are hosting malware,
(c) As far as file transfer speeds, FTP can be a bit faster for large files, while HTTP can be faster for multiple smaller files. HTTP is’ easier to work with, and it was developed specifically to address some of the inefficiencies of FTP.
(e) A program that when run, has the ability to spread to other computers on its own using either mass-mailing techniques to email addresses found on your computer or by using the Internet to infect a remote computer using known security holes.
There are several steps that should be taken for computer worm removal.

  • Check that all antivirus signatures are up-to-date.
  • Scan the computer with antivirus software.
  • If the scan detects a computer worm or other malware, use the software to remove malware and clean or delete infected files. A scan that detects no malware is usually indicative that symptoms are being caused by hardware or software problems.
  • Check that the computer’s operating system is up-to-date and all software and applications have current patches installed.
  • If a worm is difficult to remove, check online for specific computer worm removal utilities.

(f) Out of the following, following comes under cyber crime Getting in someone’s social networking account without his consent and posting pictures on his behalf to Secretly copying files from server of a call center and selling it to the other organization.
(e) (i) The most appropriate location of the server inside the CHENNAI campus (out of the 4 buildings), is ADMIN block because this block have maximum number of computers.
(iii) Firewall device will be produced by the company to be installed to protect and control the internet uses within the campus.
(iv) Video Conferencing will be best to establish the online face-to-face communication between the people in the Admin Office of CHENNAI campus and DELHI Head Office.

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