Mock Test CBSE Computer Science Class 12 Term 2 Board Examinations 2022. Practice Mock Test as per new syllabus and Exam pattern.
Total marks: 35 marks
Time : 2 Hrs
N.O of Questions : 13
Mock Test Computer Science Class 12 Term 2
Q.1. What is modulation ? What is the need of modulation? What are two main type of modulation techniques?(2 mark)
Answer: Modulation is a process of changing the characteristic of the wave to be transmitted. Modulation alters the shape of a carrier wave to encode somehow the speech or data information that is to be carried. so signals can be transferred to long distance according to the need various modulation technique exist for long travel to highly encrypted.
Q.2.What are two main type of modulation techniques? How the modulation are different than each other?(2mark)
Answer:AM(Amplitude Modulation) and FM(Frequency Modulation), In Amplitude Modulation, the strength of the carrier signal i.e., the amplitude of the modulating signal. In frequency modulation the frequency varies with frequency.
Q.3. What you understand by collisions in a network? Wired and wireless networks use different mechanism to detect and handle collisions. Name these. (2 mark)
Answer: Transmitting over a shared communication medium that at a time, only one sender and one receiver use the communication medium. If multiple nodes transmits data at the same time then the data collides known a collision and data is lost.
(wireless)CSMA/CA : Carrier sense Multiple Access/Collision avoidance
(wired)CSMA/CD : Carrier sense Multiple Access/Collision detection
Q.4. Why cannot wireless network detect collisions? What are ACK,RTS,CTS signals? (2 mark)
Answer: The wireless communication is half duplex it doesnot listen while sending that is why there is network collisions as sender keeps sending .
ACK -(acknowledgement) the receiver send data to the transmitter that this part of code has been received.
RTS/CTS (Request To Send / Clear To Send) is the optional mechanism used by the 802.11 wireless networking protocol to reduce frame collisions intrAoduced by the hidden node problem.
Q.5.What is the difference between HAVING and WHERE clause? What is the use of GROUP BY clause? (2 marks)
Answer: The difference between WHERE and HAVING clause is that WHERE condition are applicable on individual rows whereas HAVING conditions are applicable on groups as formed by GROUP BY clause. The GROUP BY clause combines all those records that have identical values in the particular field or a group of fields. Or in simple word to the make group.
Q.6.What are aggregate functions? What is their use? Give some examples. (2 marks)
Answer:The function that work on whole records of one column at a time is called aggregate functions.Or in other word Function that works on aggregate of rows. A multiple row function.
An aggregate Function retrieve a single value after performing calculation on set of values.
SUM (),MIN(),MAX(),COUNT(),AVG() etc.
Q.7.Give postfix form of the following expression A(B+(C+D)(E+F)/G)*H (2 marks)
Q.8(a). Which SQL statement allows you to find the highest price from the table BOOK_INFORMATION ? (1 mark)
(a)= SELECT B0OK_ID, BOOK_TITLE, MAX(PRICE) FROM BOOK_INFORMATION ;
(b) = SELECT MAX(PRICE) FROM BOOK_INFORMATION ;
(c)= SELECT MAXIMUM( PRICE) FROM BOOK_INFORMATION ;
(d) SELECT PRICE FROM BOOK_ INFORMATION ORDER BY PRICE DESC ;
(b) = SELECT MAX(PRICE) FROM BOOK_INFORMATION ;
Q.8 (b)Which SQL statement lets you list all stores whose total sales amount is over 5000 ? (1 mark)
(a) = SELECT STORE_ID, SUM(SALES_AMOUNT) FROM SALES GROUP BY STORE_ID HAVING SUM(SALES_AMOUNT) > 5000;
(b) = SELECT STORE_ID, SUM(SALES_AMOUNT) FROM SALES GROUP BY STORE_ID HAVING SALES_AMOUNT > 5000 ;
(c) = SELECT STORE_ID, SUM(SALES_AMOUNT) FROM SALES WHERE SUM(SALES_AMOUNT) > 5000 GROUP BY STORE_ID
(d) = SELECT STORE_ID, SUM(SALES_AMOUNT) FROM SALES WHERE SALES_AMOUNT > 5000 GROUP BY STORE_ID;
Consider this table —
Answer:(a) = SELECT STORE_ID, SUM(SALES_AMOUNT) FROM SALES GROUP BY STORE_ID HAVING SUM(SALES_AMOUNT) > 5000;
Q.8. (c) Which SQL statement lets you find the sales amount for each store ? (1 mark)
(a) = SELECT STORE_ID, SUM(SALES_AMOUNT) FROM SALES
(b) = SELECT STORE_ID, SUM (SALES_AMOUNT ) FROM SALES ORDER BY STORE_ID;
(c) = SELECT STORE_ID, SUM(SALES_AMOUNT) FROM SALES GROUP BY STORE_ID;
(d) = SELECT STORE_ID, SUM(SALES_AMOUNT) FROM SALES HAVING UNIQUE STORE_ID ;
Answer:(c) = SELECT STORE_ID, SUM(SALES_AMOUNT) FROM SALES GROUP BY STORE_ID;
Answer:(d) = SELECT COUNT (STORE_ID) FROM SALES GROUP BY STORE_ID;
|G101||Power Fit Exerciser||20000||Power Gymea|
|G102||Aquafit hand group||1800||Reliable|
|G104||Protoner Extreme Gym||30000||Cosoore|
|G105||Massage Belt||5000||Massage Expert|
|G106||Cross Trainer||13000||GTC Fitness|
(a) What is the use of UPDATE statement in SQL ? How is it different from ALTER statement . (1 mark)
(b) Mr. Shankar created a table VEHICLE with 3 rows and 4 columns. He added 1 more row to it deleted one column. What is the Cardinality and Degree of the Table VEHICLE ? (1 mark)
(c) Consider the following table named “GYM” with details about fitness items being sold in the store. Write command of SQL for (i) to (iv). (2marks)
(a)UPDATE statement in SQL is used to update the data of an existing table in database .
ALTER is a DDL (Data Definition Language) statement. Whereas the UPDATE is a DML (Data Manipulation Language) statement. ALTER is used for the update of the structure of the table (add/remove field/index etc). Whereas UPDATE is used to update data.
number of cardinality = 4
Number of degree = 3
select * from GYM
Where INAME like “A%”
select ICODE , INAME from GYM
Where BRANDNAME in ( “Reliable” , “Coscore” )
Set BRANDNAME = “Fit Trend India ”
Where ICODE = “G101”;
insert into GYM values (“G107”, “Vibro exerciser”, 21000, “GTCFitness”) ;
Q.10. Explain the working of CSMA/CA and its two implementation.(3 marks)
1.A device listens for an opportunity to transmit its data, i.e., CARRIER SENSE.
2.If the carrier is free, the sending device does not immediately transmit data.
3.Rather, it first transmits a signal notifying other devices (i.e., a warning packet) that it is transmitting for so much time before actually sending the data.
4.The other device refrains from transmitting data for the specified time limit. This means data packets will never collide, although warning packets might.
Q.11.How is FOREIGN KEY commands different and related from PRIMARY KEY command?(3 marks)
1. The Primary key can not accept null values . foreign key can accept multiple null values .
2. While only one primary key in a table while more than one foreign key in a table .
3. The primary key uniquely identify the record in the table while foreign key is a field in the table that is primary key in another table.
The foreign key is a column or a set of columns in one table that references the primary key columns in another table.
Q.12.Convert the following infix notation of expression to an equivalent postfix notation of expression (Show status of
stack after execution of each operation): (A+B)*C-D/E (4 marks)
Q.13.Differentiate between DDL and DML commands.(4marks)
1 . DDL is Data Definition Language
2 . Used to define data structure
3 . Used to define database structure or schema
4 . It uses commands are: CREATE, ALTER, DROP, TRUNCATE, RENAME
5 . Works on whole table
6 . Not have a where clause to filter
7 . The changes done by DDL commands cannot be rolled back
8 . Example — Drop table student
1 . Data Manipulation Language
2 . Used to manipulate the existing databases.
3 . Used for managing data within schema objects
4 . The commands are: SELECT, INSERT, DELETE, UPDATE, MERGE, CALL
5 . Works on one or more rows
6. Where clause to filter records
7 . The changes can be rolled back
8 . Further classified as procedural and non procedural
9 . Example — Select * from student
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