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Q:15 With respect to CRT, the horizontal retrace is defined as:

(A) The path an electron beam takes when returning to the left side of the CRT.

(B) The path an electron beam takes when returning to the right side of the CRT.

(C) The technique of turning the electron beam off while retracing.

(D) The technique of turning the electron beam on/off while retracing.


Answer: (A)

Explanation: In computer graphics Horizontal Retrace is defined as: The path an electron beam takes when returning to the left side of the CRT.

The scanning process sweeps the beam from left to right across the screen. At the end of the scanline the beam is moved to the start of the next (horizontal retrace). After the last scanline the beam is returned to the start position. (Vertical retrace).

So, option (A) is correct.

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Q:14 Which of the following is not true in case of Oblique Projections?
(A) Parallel projection rays are not perpendicular to the viewing plane.
(B) Parallel lines in space appear parallel on the final projected image.
(C) Used exclusively for pictorial purposes rather than formal working drawings.
(D) Projectors are always perpendicular to the plane of projection.


Answer: (D)

Explanation: 

 

(A) → Parallel projection rays are not perpendicular to the viewing plane. TRUE
(B) → Parallel lines in space appear parallel on the final projected image. TRUE
(C) → Used exclusively for pictorial purposes rather than formal working drawings. TRUE

(D) → Projectors are always perpendicular to the plane of projection. False

The projectors in oblique projection intersect the projection plane at an oblique angle to produce the projected image, as opposed to the perpendicular angle used in orthographic projection. 

So, option (D) is correct.

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Q:11 Given two relations R1(A, B) and R2(C, D), the result of following query

Select distinct A, B
from R1, R2

is guaranteed to be same as R1 provided one of the following condition is satisfied.
(A) R1 has no duplicates and R2 is empty.
(B) R1 has no duplicates and R2 is non – empty.
(C) Both R1 and R2 have no duplicates.
(D) R2 has no duplicates and R1 is non – empty.


Answer: (B)

Explanation: Select A,B
From R1, R2 :
In this query first we will take Cartesian product of R1, R2 (R2 must be non empty)for this 0- R2 then select distinct A,B from Cartesian product of R1, R2 (for A,B being distinct there should not any duplicate A,B).
And
Select A,B
From R2
For this query A,B → No duplicate A,B.
By combining condition for both query we will get the right condition.
So, option (B) is correct.

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Q:10 Consider a relation R (A, B, C, D, E, F, G, H), where each attribute is atomic, and following functional dependencies exist.

CH → G
A → BC
B → CFH
E → A
F → EG

The relation R is __________ .
(A) in 1NF but not in 2NF
(B) in 2NF but not in 3NF
(C) in 3NF but not in BCNF
(D) in BCNF


Answer: (A)

Explanation: If we find closure of A:

A+ → All atribute except D.
Similarly for other keys we can find closure, but D can’t be derived from any key and it must be added to all keys to be derived from. That’s why this relation is in 1NF, since there is partial dependency so, this relation is not in 2NF.
So, option (A) is correct.

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Q: 9 If every non-key attribute is functionally dependent on the primary key, then the relation is in __________ .

(A) First normal form
(B) Second normal form
(C) Third normal form
(D) Fourth normal form


Answer: (B)

Explanation: Conditions for various normal forms:

1. 1 NF – A relation R is in first normal form (1NF) if and only if all underlying domains contain atomic values only.
2. 2 NF – A relation R is in second normal form (2NF) if and only if it is in 1NF and every non-key attribute is fully dependent on the primary key.
3. 3 NF – A relation R is in third normal form (3NF) if and only if it is in 2NF and every non-key attribute is non-transitively dependent on the primary key.
4. BCNF – A relation R is in Boyce-Codd normal form (BCNF) if and only if every determinant is a candidate key.

 

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GATE 2016 SET-2 Q:32

Topic: DBMS

Q: 8 Suppose a database schedule S involves transactions T1, T2, ………….,Tn. Consider the precedence graph of S with vertices representing the transactions and edges representing the conflicts. If S is serializable, which one of the following orderings of the vertices of the precedence graph is guaranteed to yield a serial schedule ?

(A) Topological order
(B) Depth – first order
(C) Breadth – first order
(D) Ascending order of transaction indices


Answer: (A)

Explanation: For a schedule, we can check its serializability by drawing a precedence graph and find its topological order, precedence graph of schedule must not contain any cycle to be conflict free.

Cycle in precedence graph tells that schedule is not conflict serializable. DFS and BFS traversal of graph are possible even if graph contains cycle. And hence DFS and BFS are also possible for non serializable graphs. But Topological sort of any cyclic graph is not possible. Thus topological sort guarantees graph to be serializable . Option D is not valid because in a transaction with more indices might have to come before lower one. Also two non- conflicting schedule can occur simultaneously.

So, option (A) is correct.

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Question 65 GATE-CS-2014-(Set-1) | Question 65 2014 GATE

Q:7 Consider the following four schedules due to three transactions (indicated by the subscript) using read and write on a data item X, denoted by r(X) and w(X) respectively. Which one of them is conflict serializable ?

S1: r1(X); r2(X); w1(X); r3(X); w2(X)

S2: r2(X); r1(X); w2(X); r3(X); w1(X)

S3: r3(X); r2(X); r1(X); w2(X); w1(X)

S4: r2(X); w2(X); r3(X); r1(X); w1(X)

(A) S1
(B) S2
(C) S3
(D) S4


Answer: (D)

Explanation: We can draw precedence graph for each schedule and for conflict serializability graph must not contain cycle.

So, option (D) is correct.

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Q:6 A micro-instruction format has micro-ops field which is divided into three subfields F1, F2, F3 each having seven distinct micro-operations, condition field CD for four status bits, branch field BR having four options used in conjunction with address field ADF. The address space is of 128 memory locations. The size of micro-instruction is:

(A) 17
(B) 20
(C) 24
(D) 32


Answer: (B)

Explanation: Microprocessor instruction format, which is divided into three subfields F1, F2, F3 each having seven distinct micro-operations, condition field CD for four status bits, branch field BR having four options used in conjunction with address field ADF. The address space is of 128 memory locations.ie:

F1,F2,F3 each having seven distinct micro-operation. So, 3 bits are required for each.
Condition field have four status, it needs 2 bits for four different condition.
Branch field have four option so,it needs 2 bits for four option.
Now there are 128 different memory location, So, there 7 bits atre required for 128 diffeent location.
Instruction Field:
Total bits are 20.
So, option (B) is correct.

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Q:5 Which of the following is correct statement ?

(A) In memory – mapped I/O, the CPU can manipulate I/O data residing in interface registers that are not used to manipulate memory words.
(B) The isolated I/O method isolates memory and I/O addresses so that memory address range is not affected by interface address assignment.
(C) In asynchronous serial transfer of data the two units share a common clock.
(D) In synchronous serial transmission of data the two units have different clocks.


Answer: (B)

Explanation:

• The isolated I/O method isolates memory and I/O addresses so that memory address range is not affected by interface address assignment.
• Memory based I/O uses same address space for memory and I/O devices.
• In asynchronous serial transfer of data the two units do not share a common clock.
• In synchronous serial transfer of data the two units share a common clock.

Option (B) is correct.

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Q:4 Which of the following addressing mode is best suited to access elements of an array of contiguous memory locations ?

(A) Indexed addressing mode
(B) Base Register addressing mode
(C) Relative address mode
(D) Displacement mode


Answer: (A)

Explanation: Indexed addressing mode is best suited for accessing an array in contiguous memory location.

So, option (A) is correct.

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Q:3 In the architecture of 8085 microprocessor match the following:

(A) (1)
(B) (2)
(C) (3)
(D) (4)


Answer: (B)

Explanation:

• ALU is the arithmetic logic unit and it involves processing of input into desired output.
• Timing and control instruction are covered in instruction unit of microprocessor.
• There are some general purpose register in storage and interface unit.
• While an interrupt is a signal to the processor which required attention from processor, an interrupt is serviced on the basis of priority and need.

So, option (B) is correct.

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Q:2 In 8085 microprocessor the address bus is of __________ bits.
(A) 4
(B) 8
(C) 16
(D) 32


Answer: (C)

Explanation: In 8085 microprocessor 16 bits are used for address bus and 65,536(216 = 65,536) different memory location are possible.
So, option (C) is correct.

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Q:1 In 8085 microprocessor which of the following flag(s) is (are) affected by an arithmetic operation ? 

(A) AC flag Only 

(B) CY flag Only 

(C) Z flag Only 

(D) AC, CY, Z flags 

 Answer: (D) 

Explanation: AC is auxiliary-Carry flag, CY is Carry flag and Z is Zero flag. All these flags will be affected during arithmetic operation. So, option (D) is correct.