GATE CS question library

Let $X$ be a recursive language and $Y$ be a recursively enumerable but not recursive language. Let $W$ and $Z$ be two languages such that $\overline{Y}$ reduces to $W$, and $Z$ reduces to $\overline{X}$ (reduction means the standard many-one reduction). Which one of the following statements is TRUE?

Consider the following proposed solution for the critical section problem. There are $n$ processes : $P_0....P_{n-1}$. In the code, function $\text{pmax}$ returns an integer not smaller than any of its arguments .For all $i,t[i]$ is initialized to zero. Code for $P_i$; do { c[i]=1; t[i]= pmax (t[0],....,t[n-1])+1; c[i]=0; for every j != i in …

A function $f: \Bbb{N^+} \rightarrow \Bbb{N^+}$ , defined on the set of positive integers $\Bbb{N^+}$, satisfies the following properties: $f(n)=f(n/2)$ if $n$ is even $f(n)=f(n+5)$ if $n$ is odd Let $R=\{ i \mid \exists{j} : f(j)=i \}$ be the set of distinct values that $f$ takes. The maximum possible size of $R$ is ___________.

Cylinder a disk queue with requests for $I/O$ to blocks on cylinders $47, 38, 121, 191, 87, 11, 92, 10.$ The C-LOOK scheduling algorithm is used. The head is initially at cylinder number $63$, moving towards larger cylinder numbers on its servicing pass. The cylinders are numbered from $0$ to $199$. The total head movement (in number of cylinders) …

Consider the recurrence relation $a_1 =8 , a_n =6n^2 +2n+a_{n-1}$. Let $a_{99}=K\times 10^4$. The value of $K$ is __________.

An IP datagram of size $1000$ $\text{bytes }$arrives at a router. The router has to forward this packet on a link whose MTU (maximum transmission unit) is $100$ $\text{bytes }$. Assume that the size of the IP header is $20$ $\text{bytes }.$ The number of fragments that the IP datagram will be divided into for transmission is________.

Consider a computer system with ten physical page frames. The system is provided with an access sequence $(a_{1}, a_{2},....,a_{20}, a_{1}, a_{2},...a_{20})$, where each $a_{i}$ is a distinct virtual page number. The difference in the number of page faults between the last-in-first-out page replacement policy and the optimal page replacement policy …

Consider the following experiment. Step 1. Flip a fair coin twice. Step 2. If the outcomes are (TAILS, HEADS) then output $Y$ and stop. Step 3. If the outcomes are either (HEADS, HEADS) or (HEADS, TAILS), then output $N$ and stop. Step 4. If the outcomes are (TAILS, TAILS), then go to Step $1.$ The probability that the output of the experiment is $Y$ …

An operator delete$(i)$ for a binary heap data structure is to be designed to delete the item in the $i$-th node. Assume that the heap is implemented in an array and $i$ refers to the $i$-th index of the array. If the heap tree has depth $d$ (number of edges on the path from the root to the farthest leaf ), then what is the time complexity to …

Consider the following context-free grammars; $G_1 : S \to aS \mid B, B \to b \mid bB$ $G_2 : S \to aA \mid bB, A \to aA \mid B \mid \varepsilon,B \to bB \mid \varepsilon$ Which one of the following pairs of languages is generated by $G_1$ and $G_2$ ,respectively?

The following function computes the maximum value contained in an integer array $P[ \ ]$ of size $n$ $(n>=1)$. int max (int *p,int n) { int a = 0, b=n-1; while (__________) { if (p[a]<= p[b]) {a = a+1;} else {b = b-1;} } return p[a]; } The missing loop condition is:

Consider the following two phase locking protocol. Suppose a transaction $T$ accesses (for read or write operations), a certain set of objects $\{O_1,\ldots,O_k \}$. This is done in the following manner: $\text{Step 1}$. $T$ acquires exclusive locks to $O_1,\ldots,O_k$ in increasing order of their addresses. $\text{Step 2}$. The required …

What will be the output of the following pseudo-code when parameters are passed by reference and dynamic scoping is assumed? a = 3; void n(x) { x = x * a; print (x); } void m(y) { a = 1 ; a = y - a; n(a); print (a); } void main () { m(a); }

Consider the following Syntax Directed Translation Scheme $( SDTS )$, with non-terminals $\{S,A \}$ and terminals $\{a,b \}$. $S \to aA \quad \{\text{print }1\}$ $S \to a \quad \{\text{print }2\}$ $A \to Sb \quad \{\text{print }3\}$ Using the above $SDTS$ , the output printed by a bottom-up parser, for the input $aab$ is:

The size of the data count register of a $\text{DMA}$ controller is $16\;\text{bits}$. The processor needs to transfer a file of $29,154$ kilobytes from disk to main memory. The memory is byte addressable. The minimum number of times the $\text{DMA}$ controller needs to get the control of the system bus from the processor to transfer the file from …

The attribute of three arithmetic operators in some programming language are given below. …

A sender uses the Stop-and-Wait $\text{ARQ}$ protocol for reliable transmission of frames. Frames are of size $1000$ bytes and the transmission rate at the sender is $80\;\textsf{Kbps} (1\textsf{Kbps} = 1000\;\text{ bits/second}).$ Size of an acknowledgment is $100$ bytes and the transmission rate at the receiver is $8\;\textsf{Kbps.}$ The one-way …

Consider that $B$ wants to send a message $m$ that is digitally signed to $A$. Let the pair of private and public keys for $A$ and $B$ be denoted by ${K_{x}}^-$ and ${K_{x}}^+$ for $x=A, B$, respectively. Let $K_{x}(m)$ represent the operation of encrypting $m$ with a key $K_{x}$ and $H(m)$ represent the message digest. Which one of …

The coefficient of $x^{12}$ in $\left(x^{3}+x^{4}+x^{5}+x^{6}+\dots \right)^{3}$ is ___________.

The stage delays in a $4$-stage pipeline are $800, 500, 400$ and $300$ picoseconds. The first stage (with delay $800$ picoseconds) is replaced with a functionality equivalent design involving two stages with respective delays $600$ and $350$ picoseconds. The throughput increase of the pipeline is ___________ percent.