Questions

We know that, there are 7 continents in the world. They are :

Asia, Africa, Australia, North America, South America, Europe and Antarctica.

Africa - 53 countries

Asia - 48 countries

Europe - 45 countries

Antarctica - 0 countries

Hence, the continent Africa has most number of countries with 53 countries and in second place Asia has 48 , third Europe has 45 countries.

The process that allows a network to self-repair networks problems. The stations on the network notify the other stations on the ring when they are not receiving the transmissions. Beaconing is used in Token ring and FDDI networks.

Free memory is maintained in linked lists, each of equal sized blocks. Any such block is of size 2^k. When some memory is required by a process, the block size of next higher order is chosen, and broken into two. Note that the two such pieces differ in address only in their kth bit. Such pieces are called buddies. When any used block is freed, the OS checks to see if its buddy is also free. If so, it is rejoined, and put into the original free-block linked-list.

Adders are generally of five types:

1.Ripple Carry Adder:

The Ripple carry adder(RCA) consists of a building block named Half Adder(HA) which is cascaded to form a Full Adder(FA). These buildingblocks HAs and FAs are also the building blocks of all types of adders.The n full adders are cascaded to form n bit RCA.

The full adder has three input pins(input Ai,input Bi,carryin Ci) and two output pins(Sum and Ci+1).Its equations are:

Sum=Ai^Bi^Ci

Ci+1=Ai.Bi+Bi.Ci+Ai.Ci

2. Carry Lookahead Adder:

The Carry Lookahead Adder(CLA) reduces the delay as that in RCA. Let Gi=Ai.Bi, and Pi=Ai^Bi, then Ci+1=Gi+Pi.Ci.

The expressions for Sum and Ci+1 is then defined completely in terms of input pins rather wait for input carry to appear.

3. Carry Select Adder:

The carry select adder uses duplicate modules for each combination of input carry(i.e. 1 and 0).The multiplexers then select the appropriate sum and carry output according to the carry output of the preceding stages.

4. Carry Skip Adder:

The carry skip adder are as fast as carry lookahead adders which are the fastest adders but its spped decreases to about 20-30% if input operands are 64-bit or more. In these adders we divide the input bit stream into various blocks and make use of two observations:

-if each element of the two bit streams are unequal,i.e. Ai!=Bi than the carry input of the block is equal to the carry input.

-if each element of the two bit streams are equal,i.e. Ai=Bi than the carry input of the block is opposite of the carry input.

5. Carry Save Adder:

The carry save adder reduces the addition of three elements into addition of two elements,i.e. if you want sum of nine numbers it reduces it into sum of six numbers. In first step the sum of three numbers is calculated without bothering for the carry.During the second step only carry is calculated which is then added to the generated sum to give the required sum. 

The support cells of the nervous system are Glia, also called glial cells or neuroglia. In the central nervous system, there are four types of supporting cells. They are ::

* Astrocytes

* Microglial cells

* Ependymal cells

* Oligodendrocytes

A 40% solution of Formaldehyde known as Formalin is used in the preservation of biological specimens because of its hardening action on proteins. 

Defence Research and Development Organisation (DRDO) has developed an unmanned, remotely operated tank which has three variants - surveillance, mine detection and reconnaissance in areas with nuclear and bio threats. It is called Muntra.