CBSE Guess > Papers > Important Questions > Class XII > 2010 > Computer Science > Computer Science By Ravi Kiran
CBSE CLASS XII
5. (a) Primary Key: The attribute (Column) or set of attributes (Columns) which is used to identify
a tuple/row uniquely are known as Primary Key.
Degree of a relation: Number of attribute or column in a table form cardinality of a relation.
(b) (i) Select FIRSTNAME, LASTNAME, ADDRESS, CITY From EMPLOYEES
Where CITY= ‘Paris’;
convenience) of correct SQL Command]
(ii) Select * From EMPLOYEES
Order By FIRSTNAME;
(iii) Select FIRSTNAME, LASTNAME, SALARY From EMPLOYEES, EMPSALARY
Where EMPLOYEES.EMPID=EMPSALARY.EMPID;
(iv) Select Max(SALARY) From EMPSALARY
Where DESIGNATION = ‘Manager’ OR DESIGNATION = ‘Clerk’;
(v) FIRSTNAME SALARY
Rachel 32000
Peter 28000
(vi) COUNT (DISTINCT DESIGNATION)
(vii) DESIGNATION SUM(SALARY)
Manager 215000
Clerk 135000
6. (a) Associative Laws of Boolean Algebra:
A.(B.C) = (A.B).C
OR
A+(B+C) = (A+B)+C
Verification of A.(B.C) = (A.B).C
A B C B.C A.(B.C) A.B (A.B).C
0 0 0 0 0 0 0
0 0 1 0 0 0 0
0 1 0 0 0 0 0
0 1 1 1 0 0 0
1 0 0 0 0 0 0
1 0 1 0 0 0 0
1 1 0 0 0 1 0
1 1 1 1 1 1 1
7. (a) Message switching: The saurce computer sends data (message) to the
switching office, which stores data in a buffer. It then looks for a free link
to another switching office and sends data to that office. This process
continues until data is delivered to the destination computer. This type of
switching technique is also known as ‘store and forward’ switching.
Packat switching: A fixed size of packet that can be transmitted across the network is specified. All the packets are stored in the main memory instead of disk. As a result accessing time of packets is reduced.
(b) (i) Tranmission Control Protocol/Internet Protocol
(ii) eXtensible Markup Language OR extendable Markup Language
(iii) Code Division Multiple Access
(iv) Wireless in a Local Loop
(c) Cyber law encompasses a wide variety of political and legal issues related
to the Internet and other communications technology, including intellectu \\
property, privacy, freedom of expression, and jurisdiction.
Paper By Mr. Ravi Kiran
Email Id : [email protected]
