1.Which of the following is an important feature of the sum-of-products form of expressions?
a) All logic circuits are reduced to nothing more than simple AND and OR operations
b) The delay times are greatly reduced over other forms
c) No signal must pass through more than two gates, not including inverters
d) The maximum number of gates that any signal must pass through is reduced by a factor of two
Explanation: An important feature of the sum-of-products form of expressions in the given option is that all logic circuits are reduced to nothing more than simple AND and OR operations. Sum Of Product means it is the sum of product terms containing variables in complemented as well as uncomplemented forms.
2. Which of the following expressions is in the product-of-sums form?
a) (A + B)(C + D)
b) (AB)(CD)
c) AB(CD)
d) AB + CD
Explanation: (A + B)(C + D) represents the product-of-sums form.
3.Controlled inverter is also known as _____________
a) Controlled buffer
b) NOT gate
c) Both controlled buffer and NOT gate
d) Controlled gate
Explanation: Controlled inverter is also known as controlled buffer and NOT gate as well. It is used between output and a bus so that one can control whether the output is fed to the bus or not.
4. Why XOR gate is called an inverter?
a) Because of the same input
b) Because of the same output
c) It behaves like a NOT gate
d) It behaves like a AND gate
Explanation:The XOR (Exclusive Or) gate has a true output when the two inputs are different. When one input is true, the output is the inversion of the other. When one input is false, the output is the non-inversion of the other.
5. Controlled buffers can be useful __________
a) To control the circuit’s output into the bus
b) In comparison of component’s output with its input
c) In increasing the output from its low input
d) All of the Mentioned
Explanation: Controlled buffers can be useful when you have a wire (often called a bus) whose value should match the output of one of several components. By placing a controlled buffer between each component output and the bus, you can control whether that component’s output is fed onto the bus or not
6.A logic circuit that provides a HIGH output for both inputs HIGH or both inputs LOW is __________
a) Ex-NOR gate
b) OR gate
c) Ex-OR gate
d) NAND gate
Explanation: EX-OR gate gives 1 if both inputs are different means 0 or 1 and gives 0 if both are same and EX-NOR is opposite of EX-OR gate, so it provides a HIGH output for both inputs HIGH or both inputs are LOW. Thus, EX-NOR produces output for even number of 1’s or all 0s, while EXOR produces output for odd number of 1’s.
7. What is the first thing you will need if you are going to use a macro-function?
a) A complicated design project
b) An experienced design engineer
c) Good documentation
d) Experience in HDL
Explanation: HDL stands for Hardware Description Language. In order to use a macro function, one needs to have experience in HDL for representing the structure and behaviour of digital circuits
8.What is the major difference between half-adders and full-adders?
a) Full-adders are made up of two half-adders
b) Full adders can handle double-digit numbers
c) Full adders have a carry input capability
d) Half adders can handle only single-digit numbers
Explanation: Half adders have only two inputs A and B. When we add two 4 bit binary number like 0001 and 0011, then half adder can not be used because if the first bit of both the numbers is 1, then the sum would be 0 and carry would be 1. But this carry can not be added with the second bits addition of the number. So, half adders are useless. But in full adders, one more carry input is present, so that, if carry of one stage is present, it can be added with the next stage as it is done in normal addition. So, therefore, full adders have a carry input capability
9. The binary subtraction of 0 – 0 = ?
a) Difference = 0, borrow = 0
b) Difference = 1, borrow = 0
c) Difference = 1, borrow = 1
d) Difference = 0, borrow = 1
Explanation: The binary subtraction of 0 – 0 = 0. Thus, it’s difference is 0 as well as it’s borrow.
10.How many basic binary subtraction operations are possible?
a) 1
b) 4
c) 3
d) 2
Explanation: 4 basic binary subtraction operations (0-0, 1-0, 0-1, 1-1) are possible.
0 – 0 = 0
0 – 1 = 1 ( Borrow 1)
1 – 0 = 1
1 – 1 = 0