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What is the result of evaluating the following two expressions using threedigit floating point arithmetic with rounding?
(113. + 111.) + 7.51
113. + (111. + 7.51)
Let A = 1111 1010 and B = 0000 1010 be two 8bit 2’s complement numbers. Their product in 2’s complement is
A = 1111 1010 = 6
B = 0000 1010 = 10
A*B = 60
=1100 0100
Using a 4bit 2's complement arithmetic, which of the following additions will result in an overflow?
i. 1100 + 1100
ii. 0011 + 0111
iii. 1111 + 0111
Only (ii) is the answer.
In 2's complement arithmetic, overflow happens only when
1. Sign bit of two input numbers is 0, and the result has sign bit 1
2. Sign bit of two input numbers is 1, and the result has sign bit 0.
Overflow is important only for signed arithmetic while carry is important only for unsigned arithmetic.
A carry happens when there is a carry to (or borrow from) the most significant bit. Here, (i) and (iii) cause a carry but only (ii) causes overflow.
(123456)_{8} = (001 010 011 100 101 110)_{2} = (00 1010 0111 0010 1110)_{2} = (A72E)_{16}
= (00 10 10 01 11 00 10 11 10)_{2} = (22130232)_{4}
The range of integers that can be represented by an bit 2’s complement number system is:
An nbit two'scomplement numeral system can represent every integer in the range −(2^{n − 1}) to +(2^{n − 1} − 1).
while ones' complement can only represent integers in the range −(2^{n − 1} − 1) to +(2^{n − 1} − 1).
A is answer
657_{8} = (110 101 111)_{2} = (1 [10 10] [1 111])_{2} =(1AF)_{16}
We consider the addition of two 2`s complement numbers A binary adder for adding unsigned binary numbers is used to add the two numbers. The sum is denoted by and the carryout byC_{out} .
Which one of the following options correctly identifies the overflow condition?
Number representation in 2's complement representation:
So, the overflow conditions are
1. When we add two positive numbers (sign bit 0) and we get a sign bit 1
2. When we add two negative numbers (sign bit 1) and we get sign bit 0
3. Overflow is relevant only for signed numbers and we use carry for Unsigned numbers
4. When the carry out bit and the carry in to the most significant bit differs
PS: When we add one positive and one negative number we won't get a carry. Also points 1 and 2 is leading to point 4.
Now the question is a bit tricky. It is actually asking the condition of overflow of signed numbers when we use an adder
which is meant to work for unsigned numbers.
So, if we see the options, B is the correct one here as the first part takes care of case 2 (negative numbers) and the second part takes care of case 1 (positive numbers)  point 4. We can see a counter example each for other options:
A  Let n = 4 and we do 0111 + 0111 =. This overflows as in 2`s complement representation we can store only up to 7. But the overflow condition in A returns false as .
C_{out} = 0.
C  This works for the above example. But fails for 1001 + 0001 = 1010 where there is no actual overflow (7+1 = 6), but the given condition gives an overflow as C_{out} = 0 and c_{n1} = 1.
D  This works for both the above examples, but fails for 1111 + 1111 = 1110 (1 + 1 = 2) where there is no actual overflow but the given condition says so.
The addition of 4bit, two's complement, binary numbers 1101 and 0100 results in
The addition results in 0001 and no overflow with 1 as carry bit.
In 2's complement addition Overflow happens only when :
(C012.25)_{H}  (10111001110.101)_{B}
= 1100 0000 0001 0010. 0010 0101
 0000 0101 1100 1110. 1010 0000
= 1011 1010 0100 0011. 1000 0101
= 1 011 101 001 000 011 . 100 001 010
= (135103.412)o
Binary subtraction is like decimal subtraction: 00 = 0, 11 = 0, 10 = 1, 01 = 1 with 1 borrow
Let r denote number system radix. The only value(s) of r that satisfy the equation
So any integer r satisfies this but r must be > 2 as we have 2 in 121 and radix must be greater than any of the digits .(D) is the most appropriate answer
A processor that has carry, overflow and sign flag bits as part of its program status word (PSW) performs addition of the following two 2's complement numbers 01001101 and 11101001. After the execution of this addition operation, the status of the carry, overflow and sign flags, respectively will be:
01001101
+ 11101001

100110110
Carry = 1
Overflow = 0 (In 2's complement addition Overflow happens only when : Sign bit of two input numbers is 0, and the result has sign bit 1 OR Sign bit of two input numbers is 1, and the result has sign bit 0.)
Sign bit = 0
P is a 16bit signed integer. The 2's complement representation of P is (F87B)_{16}. The 2's complement representation of
Multiplication can be directly carried in 2's complement form. F87B = 1111 1000 0111 1011 can be left shifted 3 times to give 8P = 1100 0011 1101 1000 = C3D8.
Or, we can do as follows:
MSB in (F87B) is 1. So, P is a negative number. So, P = 1 * 2's complement of (F87B) = 1 * (0785) = 1 * (0000 0111 1000 0101)
8 * P = 1 * (0011 1100 0010 1000) (P in binary left shifted 3 times)
In 2's complement representation , this equals, 1100 0011 1101 1000 = C3D8
The smallest integer that can be represented by an 8bit number in 2's complement form is
Range of 2's compliment no = > ( 2^{n1})to + (2^{n1}  1)
Here n = No of bits = 8.
So minimum no = 2 ^ 7 = (B) 128
The base (or radix) of the number system such that the following equation holds is____________. 312/20 = 13.1
Let ‘x’ be the base or radix of the number system .
The equation is : (3.x^{2}+1.x1+2.x^{0}) /(2.x^{1} +0.x^{0}) =1.x^{1} +3.x^{0} +1.x^{1}
=>(3.x^{2}+x +2) /(2.x) =x +3 +1/x
=>(3.x^{2}+x +2) /(2.x) =(x^{2 }+3x +1) /x
By solving above quadratic equation you will get x=0 and x=5
As base or radix of a number system cannot be zero, here x = 5
Consider the equation (123)_{5} = (x8)_{y} with x and y as unknown. THe number of possible solutions is ______.
Changing (123) base 5 into base 10= 1*25+2*5+3*1=38
Changing x8 base y in decimal= x*y+8
Equating both we get xy+8=38
xy=30
possible combinations =(1,30)(2,15),(3,10)
but we have ‘8’ present in x8 so base y>8 as all three are satisfying the conditions so total solutions =3
Consider the equation (43)x = (y3)_{8} where x and y are unknow. The number of possible solutions is _____
(43)_{x} = (y3)_{8}
Since a number in base k can only have digits from 0 to (k1), we can conclude that: x > 5 and y < 7
Now, the original equation, when converted to decimal base gives:
So, we have the following constraints:
The set of values of (x,y) that satisfy these constraints are:
I am counting 5 pairs of values.
When two 8bit numbers complement representation (with A_{0} and B_{0} as the least significant bits) are added using a ripplecarry adder, the sum bits obtained are and the carry bits are . An overflow is said to have occurred if
Overflow is said to occur in the following cases
The 3rd condition occurs in the following case A7B7S7', now the question arises how ?
NOW, A7=1 AND B7=1 S7=0 is only possible when C6=0 otherwise s7 would become 1 C7 has to be 1 (1+1+0 generates carry)
ON similar basis we can prove that C7=0 and C6=1 is produced by A7'B7'S7. Hence either of the two conditions cause overflow . Hence ans is C .
Why not A ? when C7=1 and C6 =1 this doesnt indicate overflow (4th row in the table)
Why not B ? if all carry bits are 1 then C7=1 and C6=1 (This also generates 4th row)
Why not D ? These combinations are C0 and C1 , the lower carrys dont indicate overflow
The representation of the value of a 16  bit unsigned integer X in hexadecimal number system is BC A9. The representation of the value of X in octal number system is
Given: ( BCA9)_{16}
1011 1100 1010 1001
....for octal number system...grouping of three three bits from right to left..
Answer: Option D (1 3 6 2 5 1)_{8}
A variable that takes thirteen possible values can be communicated using?
As there are only 13 possible values variable can take, we can use ceil [log13] = 4 bits. As variable can take only 13 values we don't need to worry what those values are. Answer
: Option D
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