1Which of the following represents the decimal number $25$ in binary?
A.
B.
C.
D.
Correct Answer:
Explanation:To convert decimal to binary, divide by 2 repeatedly and record remainders: rem $1$; rem $0$; rem $0$; rem $1$; rem $1$. Reading remainders bottom-up gives .
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2Convert the hexadecimal number to its decimal equivalent.
A.$29$
B.$30$
C.$31$
D.$28$
Correct Answer: $30$
Explanation:Hexadecimal is calculated as: (since ). .
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3What is the decimal value of the binary number ?
A.$5.50$
B.$5.25$
C.$5.75$
D.$5.35$
Correct Answer: $5.75$
Explanation:Integer part . Fractional part . Total is $5.75$.
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4Which of the following is an unweighted code?
A.BCD Code
B.8421 Code
C.Excess-3 Code
D.2421 Code
Correct Answer: Excess-3 Code
Explanation:Excess-3 is a non-weighted code because the position of the bits does not correspond to a specific weight/value, unlike BCD (8421) where positions represent powers of 2.
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5Convert the binary number to Gray code.
A.$1011$
B.$1010$
C.$1110$
D.$1100$
Correct Answer: $1011$
Explanation:To convert Binary to Gray: MSB stays the same. Subsequent bits are XORed with the previous bit. MSB=$1$. Next=. Next=. Next=. Result: $1011$.
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6The Gray code $1011$ represents which binary number?
A.
B.
C.
D.
Correct Answer:
Explanation:Gray to Binary: MSB stays same ($1$). Next Binary = (Previous Binary) (Current Gray). . . . Result: .
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7What is the BCD (8421) representation of decimal number $12$?
A.$00010010$
B.$1100$
C.$00001100$
D.$00100001$
Correct Answer: $00010010$
Explanation:In BCD, each decimal digit is represented by a 4-bit binary group. , . Combined: $0001 0010$.
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8What is the Excess-3 code for the decimal number $6$?
A.$1000$
B.$0110$
C.$1001$
D.$1100$
Correct Answer: $1001$
Explanation:Excess-3 is calculated by adding 3 to the decimal number and converting to binary. . Binary of $9$ is $1001$.
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9The 2's complement of the binary number $10110$ is:
A.$01001$
B.$01010$
C.$01011$
D.$10111$
Correct Answer: $01010$
Explanation:To find 2's complement: Invert all bits () and add 1 ().
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10In 8-bit 2's complement representation, what is the range of integers that can be represented?
A.-127 to +128
B.-128 to +127
C.-256 to +255
D.0 to 255
Correct Answer: -128 to +127
Explanation:For bits, the range of signed 2's complement numbers is to . For , range is to .
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11Perform the subtraction using 2's complement method.
12Which logic gate is known as the 'Universal Gate'?
A.AND
B.XOR
C.NAND
D.OR
Correct Answer: NAND
Explanation:NAND and NOR gates are universal gates because any other boolean logic gate or function can be implemented using only combinations of them.
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13The output of an XOR gate is HIGH only when:
A.Both inputs are LOW
B.Both inputs are HIGH
C.The inputs are different
D.The inputs are the same
Correct Answer: The inputs are different
Explanation:The Exclusive-OR (XOR) gate outputs a 1 (HIGH) if and only if the inputs are not equal ($0,1$ or $1,0$).
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14Which boolean law states that ?
A.Absorption Law
B.Distributive Law
C.Redundancy Law
D.De Morgan's Law
Correct Answer: Redundancy Law
Explanation:This is a standard simplification often derived from distribution: . It effectively removes the redundant .
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15According to De Morgan's first theorem, is equal to:
A.
B.
C.
D.
Correct Answer:
Explanation:De Morgan's laws state that the complement of a sum is equal to the product of the complements: .
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16A 4-variable K-Map contains how many cells?
A.8
B.12
C.16
D.32
Correct Answer: 16
Explanation:The number of cells in a Karnaugh map is , where is the number of variables. For 4 variables, .
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17In a K-Map, grouping 4 adjacent $1$s (a quad) eliminates how many variables from the term?
A.1
B.2
C.3
D.
Correct Answer: 2
Explanation:Grouping cells eliminates variables. A quad is 4 cells (), so it eliminates 2 variables.
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18The canonical sum of products (SOP) form consists of terms called:
A.Maxterms
B.Minterms
C.Midterms
D.Sumterms
Correct Answer: Minterms
Explanation:In Canonical SOP, every term contains all variables (either complemented or uncomplemented) ANDed together. These product terms are called Minterms.
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19Convert the octal number to binary.
A.
B.
C.
D.
Correct Answer:
Explanation:Convert each octal digit to 3-bit binary. , . Concatenated: .
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20What is the 9's complement of the decimal number $27$?
A.$72$
B.$73$
C.$82$
D.$28$
Correct Answer: $72$
Explanation:The 9's complement is found by subtracting each digit from 9. .
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21The boolean expression simplifies to:
A.$0$
B.$1$
C.
D.
Correct Answer: $1$
Explanation:This expression covers all possible combinations of A and B (minterms ). The sum of all minterms in a truth table is always $1$.
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22Which of the following codes is known as a self-complementing code?
A.8421 BCD
B.Excess-3
C.Gray Code
D.Octal
Correct Answer: Excess-3
Explanation:Excess-3 is self-complementing because the 9's complement of a decimal number can be obtained by simply inverting the bits of its Excess-3 code.
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23The simplified boolean expression for the K-Map grouping involving corners of a 4-variable map ($0000, 0010, 1000, 1010$) is:
A.
B.
C.
D.
Correct Answer:
Explanation:Corners correspond to indices 0, 2, 8, 10. In variables : 0($0000$), 2($0010$), 8($1000$), 10($1010$). is always $0$ () and is always $0$ (). and change. Result: .
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24The symbol represents which form?
A.Canonical POS
B.Canonical SOP
C.Simplified SOP
D.Standard POS
Correct Answer: Canonical SOP
Explanation:The summation symbol followed by denotes a Sum of Minterms, which is the Canonical Sum of Products (SOP) form.
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25In boolean algebra,
A.
B.
C.
D.$1$
Correct Answer:
Explanation:This is the Absorption Law. .
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26Which gate is equivalent to an AND gate followed by a NOT gate?
A.NOR
B.NAND
C.XOR
D.XNOR
Correct Answer: NAND
Explanation:NAND stands for NOT-AND. It is logically equivalent to an AND operation whose output is inverted.
28A digital circuit that produces a logic $1$ output when the input number of $1$s is odd is:
A.XNOR gate
B.XOR gate
C.AND gate
D.OR gate
Correct Answer: XOR gate
Explanation:An XOR gate (or a chain of them) acts as an odd parity detector. For 2 inputs, it is 1 if inputs are different (one 1, one 0 - odd number of 1s).
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29If and , what is the value of ?
A.$0$
B.$1$
C.Indeterminate
D.High Impedance
Correct Answer: $1$
Explanation:. . . Total sum .
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30The dual of the boolean expression is:
A.
B.
C.
D.
Correct Answer:
Explanation:To find the dual, swap OR () with AND () and vice versa, and swap 0s with 1s. becomes .
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31In a 3-variable K-map, the cells and are considered:
A.Diagonal
B.Adjacent
C.Opposite
D.Isolated
Correct Answer: Adjacent
Explanation:K-maps wrap around. The top edge and bottom edge are adjacent. In a flat layout, column 00 and column 10 (if organized as gray code columns) might not look adjacent, but logically, minterms differing by one bit ($000$ and $100$ differ only in MSB) are adjacent.
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32Which of the following is equivalent to the Boolean function ?
A.
B.
C.
D.
Correct Answer:
Explanation:For variables, the total indices are 0, 1, 2, 3. If Maxterms are 0 and 3, the Minterms must be the remaining indices: 1 and 2.
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33Convert the binary fraction to decimal.
A.$0.625$
B.$0.500$
C.$0.725$
D.$0.375$
Correct Answer: $0.625$
Explanation:.
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34What is the radix of the octal number system?
A.2
B.8
C.10
D.16
Correct Answer: 8
Explanation:The radix (or base) of the Octal system is 8 (digits 0-7).
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35The boolean expression is equivalent to:
A.
B.
C.
D.
Correct Answer:
Explanation:Distributive law: .
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36To perform binary subtraction using 1's complement:
A.Add to 1's complement of . If carry generated, add 1 to sum.
B.Add to 1's complement of . If carry generated, ignore it.
C.Add to .
D.Subtract directly.
Correct Answer: Add to 1's complement of . If carry generated, add 1 to sum.
Explanation:In 1's complement subtraction, if an end-around carry is generated, it must be added to the LSB of the result.
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37What is the minimum number of NAND gates required to implement an OR gate?
A.2
B.3
C.4
D.1
Correct Answer: 3
Explanation:. Step 1: Invert A (1 NAND). Step 2: Invert B (1 NAND). Step 3: NAND them (1 NAND). Total 3 gates.
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38In K-Map simplification, 'Don't Care' conditions are represented by:
A.1
B.
C.X
D.Z
Correct Answer: X
Explanation:Don't care conditions are input combinations that never occur or whose output doesn't matter. They are marked with an 'X' and can be grouped as either 0 or 1 to optimize simplification.
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39The Gray code is often used in:
A.Arithmetic operations
B.Shaft position encoders
C.Error correction
D.Floating point operations
Correct Answer: Shaft position encoders
Explanation:Gray codes are used in position encoders because only one bit changes at a time between adjacent values, reducing errors during transition.
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40Which of the following corresponds to the Logic equation ?
A.NAND
B.NOR
C.XOR
D.XNOR
Correct Answer: XOR
Explanation:This is the standard sum-of-products definition for the Exclusive-OR (XOR) function.
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41What is the 1's complement of $100100$?
A.$011011$
B.$011100$
C.$100101$
D.$011010$
Correct Answer: $011011$
Explanation:The 1's complement is obtained by simply flipping every bit. , . .
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42Convert decimal $13$ to Excess-3 code.
A.$10000$
B.$01000110$
C.$0100$
D.$1101$
Correct Answer: $10000$
Explanation:. Binary of $16$ is $10000$.
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43The distributive law applies to:
A.Only boolean algebra
B.Only ordinary algebra
C.Both boolean and ordinary algebra
D.Neither
Correct Answer: Both boolean and ordinary algebra
Explanation:The distributive law holds true in both standard algebraic systems and Boolean logic.
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44If a 3-input NAND gate has inputs , the output is:
A.
B.1
C.High Impedance
D.Undefined
Correct Answer: 1
Explanation:NAND output is Low (0) only if all inputs are High (1). Since , the AND result is 0, and the NOT (NAND) result is 1.
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45The standard POS form of the expression corresponds to:
A.Sum of Minterms
B.Product of Maxterms
C.Product of Minterms
D.Sum of Maxterms
Correct Answer: Product of Maxterms
Explanation:POS stands for Product of Sums. In standard/canonical form, these sum terms are called Maxterms.
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46The binary code for Hexadecimal is:
A.$1010$
B.$1011$
C.$1100$
D.$1101$
Correct Answer: $1100$
Explanation:Hex digits: . Binary for $12$ is $1100$.
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47Which theorem allows moving a bubble from the output of an AND gate to the inputs, changing the gate to OR?
A.Consensus Theorem
B.De Morgan's Theorem
C.Duality Theorem
D.Superposition Theorem
Correct Answer: De Morgan's Theorem
Explanation:De Morgan's theorem conceptually allows 'breaking the bar and changing the sign', essentially swapping NAND for Negative-OR (bubbled inputs on OR).
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48Overflow in 2's complement addition occurs when:
A.Adding a positive and a negative number
B.Carry out occurs from MSB
C.Adding two numbers of same sign yields a result of opposite sign
D.Always when carry out is 1
Correct Answer: Adding two numbers of same sign yields a result of opposite sign
Explanation:Overflow happens if two positives sum to a negative (MSB 1) or two negatives sum to a positive (MSB 0) within the fixed bit width.
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49In a 4-variable K-Map, how are the rows and columns labeled?
A.Binary Sequence ($00, 01, 10, 11$)
B.Gray Code ($00, 01, 11, 10$)
C.Randomly
D.Decimal Order
Correct Answer: Gray Code ($00, 01, 11, 10$)
Explanation:Axes must use Gray code ordering so that adjacent cells differ by exactly one bit, enabling the grouping logic.
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50The value of in boolean algebra is:
A.$1$
B.
C.
D.
Correct Answer: $1$
Explanation:In boolean algebra, $1$ OR anything is always $1$ (High).
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