TNPSC2012PolytechnicCS
Question 1 
Which of the following computers is least powerful?
Mini  
Micro
 
Mainframe  
Super 
Question 1 Explanation:
Micro computer is the least powerful computer and super computer is the most powerful computer.
Question 2 
The technique which repeatedly uses the same block of internal storage during different stages of problem is called
Overlay  
Overlapping  
Swapping  
Reuse 
Question 2 Explanation:
In a general computing sense, overlaying means "the process of transferring a block of program code or other data into main memory, replacing what is already stored". Overlaying is a programming method that allows programs to be larger than the computer's main memory.
Question 3 
The number of instructions needed to add n numbers and store the result in memory using only one address instruction is
n  
n+1  
n1  
independent of n

Question 3 Explanation:
At first instruction we will load the first no. in accumulator and then from second instruction we will add remaining n1 no. using accumulator. Till now n instruction is used. And finally we will use one more instruction to store the result back to memory. So in total n+1 instruction is required.
Question 4 
The most relevant addressing mode to write position independent code is
Direct mode  
Indirect mode
 
Relative mode  
Indexed mode 
Question 4 Explanation:
Relative mode is the most relevant addressing mode to write position independent code.
Indexed mode is for arrays and structure.
Indirect mode is used for pointers.
Indexed mode is for arrays and structure.
Indirect mode is used for pointers.
Question 5 
The CPU of a computer takes instruction from the memory and executes them. This process is called
Load cycle  
Time sequences  
Fetchexecute cycle  
Clock cycle 
Question 5 Explanation:
The process in which a CPU of a computer takes instruction from memory and executes them is called fetchexecute cycle.
Question 6 
A five figure number is formed by the digits 0, 1, 2, 3, 4 without repetition. Then probability that the number formed is divisible by 4 in
3/15  
5/16  
7/16  
9/16 
Question 7 
If A and B be sets with cardinalities m and n respectively, then number of oneone mappings (injections) from A to B, when m < n, is
m^{n}  
^{n}P_{m}  
^{n}C_{m}  
None of these 
Question 7 Explanation:
The formula for above given question is ^{n}P_{m}.
Question 8 
The set of all n^{th} roots of unity under multiplication of complex numbers form a/an
Semigroup with identity  
Communicative semi groups with identity  
Group  
Abelian group 
Question 8 Explanation:
More generally, if C is a group and z∈C with z^{n} = 1, where 1 is the identity of C, then G = {1,z,z^{2},...,z^{n1}} is a group (actually, a subgroup of C).
Indeed:
• Closure: z^{j}z^{k} = z^{j+k} = z^{r} ∈ G, where r = (j+k) mod n.
• Associativity: comes from C.
• Identity: 1 ∈ G by definition, and 1 is the identity of C.
• Inverse: z^{j}z^{nj} = 1.
• Commutativity: z^{j}z^{k} = z^{j+k} = z^{k+j} = z^{k}z^{j}.
Indeed:
• Closure: z^{j}z^{k} = z^{j+k} = z^{r} ∈ G, where r = (j+k) mod n.
• Associativity: comes from C.
• Identity: 1 ∈ G by definition, and 1 is the identity of C.
• Inverse: z^{j}z^{nj} = 1.
• Commutativity: z^{j}z^{k} = z^{j+k} = z^{k+j} = z^{k}z^{j}.
Question 9 
How many 10 digit numbers can be written by using the digits 1 and 2?
10 C_{1} + 9 C_{2}  
2^{10}  
10 C_{2}  
10 1 
Question 9 Explanation:
For each digit we have two choices ‘1 or 2’. So no. of possible 10 digits nos.
2*2*2*2*2*2*2*2*2*2 = 2^{10}
2*2*2*2*2*2*2*2*2*2 = 2^{10}
Question 10 
T is a graph with n vertices. T is connected and has exactly n – 1 edges. Then
T is a tree  
T contains no cycles
 
Every pair of vertices in T is connected by exactly one path  
Addition of a new edge will create a cycle 
Question 10 Explanation:
Any graph with n vertices and n1 edges which is connected will definitely be a tree.
Question 11 
Eigenvectors of a real symmetric matrix corresponding to different eigenvalues are
Orthogonal  
Singular  
Nonsingular  
None of these 
Question 11 Explanation:
Eigenvectors of a real symmetric matrix corresponding to different eigenvalues are orthogonal to each other.
Question 12 
If L_{1} and L_{2} are context free language and R is a regular set. Which one of the languages below is not necessarily a context free language?
L_{1}L_{2}  
L_{1}∩L_{2}  
L_{1}∪R  
L_{1}∪L_{2} 
Question 12 Explanation:
Context free language is not closed under intersection. Hence B is the correct option.
Question 13 
CSG can be recognized by
pushdown automata  
2 way linear bounded automaton  
finite state automata  
none of these 
Question 13 Explanation:
Context sensitive grammar can be recognized by linear bounded automata.
Question 14 
Consider the following grammar:
S → Ax By A → ByCw B → xBw C → yWhich of the regular expressions describes the same set of strings as the grammar?
xw+y+xw*yx+ywx  
xwy+xw*xy*ywx
 
xw*y+xw*yx+ywx  
xwxy+xww*yywx 
Question 14 Explanation:
Option A do not contain xy which is generated by the grammar.
Option B do not contain xy which is generated by the grammar.
Option C do not contain xy which is generated by the grammar.
Option B do not contain xy which is generated by the grammar.
Option C do not contain xy which is generated by the grammar.
Question 15 
Recursively enumerable languages are not closed under
Union  
Intersection  
Complementation  
Concatenation 
Question 15 Explanation:
Recursively enumerable language are not closed under complementation.
Question 16 
Turing machine is more powerful than FMs because
Tape movement is confined to one direction  
It has no finite state  
It has the capability to remember arbitrarily long sequences of input symbols  
None of these

Question 16 Explanation:
Turing machines is more powerful than finite machines because it has the capability to remember arbitrarily long sequences of input symbols.
Question 17 
Which of the following statements is wrong?
The language accepted by finite automata is the languages denoted by regular expressions.
 
For every DFA there is a regular expression denoting its language
 
For a regular expression r, there does not exist any NFA with transit that accepts L(r)  
None of these 
Question 17 Explanation:
NFA, DFA and regular expression are equal in power. So for every regular expression there exists DFA and NFA.
Question 18 
Can a DFA simulate NFA?
No  
Yes
 
Sometimes  
Depends of NFA

Question 18 Explanation:
DFA has equal power as NFA.
Question 19 
Let a and b be the regular expressions, then (a*∪b*)* is not equivalent to
(a∪b)*  
(b*∪a*)*  
(b∪a)*  
(a∪b) 
Question 19 Explanation:
The given regular expression is not equal to option D.
Question 20 
FDDI is a
Ring network  