Number Systems


Question 1
If (1235)_{x}\:=\:(3033)_{y}, where x and y indicate the bases of the corresponding numbers, then
A
x\:=\:7 and y\:=\:5
B
x\:=\:8 and y\:=\:6
C
x\:=\:6 and y\:=\:4
D
x\:=\:9 and y\:=\:7
GATE EC 2021   Digital Circuits
Question 1 Explanation: 
x^{3}+2 x^{2}+3 x+5=3 y^{3}+3 y+3
Option (B) will satisfy the equation.
Question 2
P, Q, and R are the decimal integers corresponding to the 4-bit binary number 1100 considered in signed magnitude, 1's complement, and 2's complement representations, respectively. The 6-bit 2's complement representation of (P+Q+R) is
A
110101
B
110010
C
111101
D
111001
GATE EC 2020   Digital Circuits
Question 2 Explanation: 
Given, binary number 1100
1's complement of 1100 = -3
Sign magnitude of 1100 = -4
2's complement of 1100 = -4
P + Q + R = -4 - 3 - 4 = -11
The 6 digit 2's complement of (-11) = 110101


Question 3
The number of bytes required to represent the decimal number 1856357 in packed BCD (Binary Coded Decimal) form is_______.
A
2
B
3
C
4
D
5
GATE EC 2014-SET-2   Digital Circuits
Question 3 Explanation: 
To represent decimal number into BCD number each decimal number is represented in 4 -bits while converting in BCD numbers, as
\begin{array}{ll}1 \rightarrow 0001 & 6 \rightarrow 0110 \\ 8 \rightarrow 1000 & 3 \rightarrow 0011 \\ 5 \rightarrow 0101 & 5 \rightarrow 0101 \\ & 7 \rightarrow 0111\end{array}


So total 4 bytes are required.
Question 4
The two numbers represented in signed 2's complement form are P = 11101101 and Q = 11100110. If Q is subtracted from P, the value obtained in signed 2's complement is
A
1000001111
B
00000111
C
11111001
D
111111001
GATE EC 2008   Digital Circuits
Question 4 Explanation: 
\because Signed 2 's complement of
\begin{aligned} P&=11101101\\ \therefore \text{No.} \quad P&=00010011 \end{aligned}
\because Signed 2 's complement of
\begin{aligned} Q &=11100110 \\ P-Q=P+(2 ' s& \text { complement of }Q) \\ &=00010011 \\ &\frac{+11100110}{11111001} \\ \text{2's complement of }\\ (P-Q)&=00000111 \end{aligned}
Question 5
X = 01110 and Y =11001 are two 5-bit binary numbers represented in two's complement format. The sum of X and Y represented in two's complement format using 6 bits is
A
100111
B
001000
C
000111
D
101001
GATE EC 2007   Digital Circuits
Question 5 Explanation: 
\begin{array}{cccccccc} x &=&&0&1&1&1&0 \\ Y &=&&1&1&0&0&1 \\ x+y &=&1&0&0&1&1&1 \end{array}
Carry is discarded in the addition of numbers represented in 2's complement form. X + Y in 6 bits is 000111.


There are 5 questions to complete.