1.
In which of the following base systems is 123 not a valid number?
Correct Answer
D. Base 3
Explanation
In base 3, the valid digits are 0, 1, and 2. Since the number 123 contains the digit 3, it is not a valid number in base 3.
2.
Storage of 1 KB means the following number of bytes
Correct Answer
D. 1064
3.
What is the octal equivalent of the binary number:10111101
Correct Answer
B. 275
Explanation
The octal equivalent of the binary number 10111101 is 275. In octal, each digit represents three bits of the binary number. Starting from the rightmost digit, we group the binary number into sets of three bits: 101 111 01. Then, we convert each set of three bits to its octal equivalent: 101 is equivalent to 5, 111 is equivalent to 7, and 01 is equivalent to 1. Therefore, the octal equivalent of the binary number 10111101 is 275.
4.
Pick out the CORRECT statement:
Correct Answer
C. It is not always possible to find the exact binary
Explanation
The statement "It is not always possible to find the exact binary" is correct because in some cases, when representing a decimal number in binary form, the binary representation may be an infinitely repeating decimal. In such cases, it is not possible to find the exact binary representation.
5.
The binary code of (21.125)_{10} is
Correct Answer
A. 10101.001
Explanation
The given decimal number is 21.125. To convert it into binary, we can use the method of successive division by 2. We divide the integer part of the decimal number by 2 repeatedly until we reach 0, and then we concatenate the remainders in reverse order. For the fractional part, we multiply it by 2 repeatedly until we reach 0, and then we concatenate the whole numbers. The binary representation of 21 is 10101, and the binary representation of 0.125 is 001. Therefore, the correct binary representation of 21.125 is 10101.001.
6.
A NAND gate is called a universal logic element because
Correct Answer
B. Any logic function can be realized by NAND gates alone
Explanation
NAND gates are called universal logic elements because they can be used to implement any logic function. This means that any complex logic circuit can be built using only NAND gates. This property is known as functional completeness. By properly connecting and combining NAND gates, any Boolean function can be realized. This makes NAND gates a versatile and powerful component in digital circuit design. Additionally, the other options mentioned in the question, such as being used by everybody or many digital computers using NAND gates, are not accurate explanations for why NAND gates are considered universal logic elements.
7.
Digital computers are more widely used as compared to analog computers, because they are
Correct Answer
C. Useful over wider ranges of problem types
Explanation
Digital computers are more widely used compared to analog computers because they are useful over wider ranges of problem types. This means that digital computers can handle a wider variety of problems and tasks, making them more versatile and adaptable. They can be used in various industries and fields, such as finance, engineering, and healthcare, where different types of problems need to be solved. In contrast, analog computers are limited in the types of problems they can solve, making them less useful in many situations.
8.
Most of the digital computers do not have floating point hardware because
Correct Answer
A. floating point hardware is costly
Explanation
Most digital computers do not have floating point hardware because it is costly. Adding floating point hardware to a computer system requires additional components and resources, which can significantly increase the cost of the computer. Therefore, many computer manufacturers choose not to include floating point hardware in their standard models to keep the overall cost of the computer affordable for the average consumer.
9.
The number 1000 would appear just immediately after
Correct Answer
D. All of the above
Explanation
The number 1000 is represented as 1111 in binary, FFFF in hex, and 7777 in octal. Therefore, it would appear just immediately after all of the given options.
10.
(10101)_{2} is
Correct Answer
A. (21)10
Explanation
The given number in binary form is (10101)2. To convert it to decimal form, we can use the place value method. Starting from the rightmost digit, we have 1 in the 2^0 place, 0 in the 2^1 place, 1 in the 2^2 place, 0 in the 2^3 place, and 1 in the 2^4 place. Calculating the decimal value, we get 1 + 0 + 4 + 0 + 16 = 21. Therefore, the decimal equivalent of (10101)2 is (21)10.
11.
The number of Boolean functions that can be generated by n variables is equal to
Correct Answer
B. 22 n
Explanation
The correct answer is 2^n. This is because for each variable, there are two possible values (True or False), and since there are n variables, the total number of possible combinations is 2^n.
12.
Consider the representation of six-bit numbers by two’s complement, one’s complement, or by sign and magnitude: In which representation is there overflow from the addition of the integers 011000 and 011000?
Correct Answer
D. All three representations
Explanation
In all three representations (two's complement, one's complement, and sign and magnitude), there will be an overflow from the addition of the integers 011000 and 011000. This is because the sum of these two numbers exceeds the maximum value that can be represented with six bits in each of these representations.
13.
A hexadecimal odometer displays F 52 F. The next reading will be
Correct Answer
D. F53O
Explanation
The correct answer is F53O. In hexadecimal, the digits range from 0 to F. Since the last digit is F, the next digit will be 0 and the digit before it will be incremented by 1. Therefore, the next reading will be F53O.
14.
Positive logic in a logic circuit is one in which
Correct Answer
D. logic 0 voltage level is lower than logic 1 voltage level
Explanation
In positive logic, logic 0 is represented by a lower voltage level compared to logic 1. This means that a lower voltage level corresponds to a logical 0 and a higher voltage level corresponds to a logical 1.
15.
Which of the following gate is a two-level logic gate
Correct Answer
C. EXCLUSIVE OR gate
Explanation
An EXCLUSIVE OR gate is a two-level logic gate because it can be implemented using only two levels of logic gates. It requires two inputs and produces an output based on whether the inputs are different or not. The output is true only when one of the inputs is true and the other is false. This gate is commonly used in digital systems for various applications such as error detection and data transmission.
16.
Among the logic families, the family which can be used at very high frequency greater than 100 MHz in a 4 bitsynchronous counter is
Correct Answer
C. ECL
Explanation
ECL (Emitter-Coupled Logic) is the logic family that can be used at very high frequencies greater than 100 MHz in a 4-bit synchronous counter. ECL is known for its high-speed operation and is commonly used in applications that require high-performance and high-frequency operation. It uses a differential amplifier configuration that allows for fast switching times and low propagation delays, making it suitable for high-speed applications. TTLAS, CMOS, and TTLLS are not typically used at frequencies greater than 100 MHz in a 4-bit synchronous counter.
17.
An AND gate will function as OR if
Correct Answer
D. All the inputs and outputs are complemented
Explanation
When all the inputs and outputs of an AND gate are complemented, it means that the inputs and outputs are inverted. In other words, if the original inputs were "1", they are now "0", and if the original inputs were "0", they are now "1". This inversion of inputs and outputs effectively changes the behavior of the AND gate, making it function as an OR gate.
18.
An OR gate has 6 inputs. The number of input words in its truth table are
Correct Answer
C. 64
Explanation
An OR gate with 6 inputs can have a total of 64 possible combinations of inputs. This is because each input can be either 0 or 1, and there are 6 inputs in total. So, the number of input words in the truth table would be 64.
19.
A debouncing circuit is
Correct Answer
C. A latch
Explanation
A debouncing circuit is a latch. A latch is a type of digital circuit that has two stable states and can store information. In the context of debouncing, a latch is used to stabilize a signal by removing any noise or fluctuations. It ensures that only a single stable state is maintained, preventing multiple transitions caused by temporary changes in the input signal. Therefore, a latch is the most appropriate type of circuit for debouncing purposes.
20.
NAND. gates are preferred over others because these
Correct Answer
B. Can be used to make any gate
Explanation
NAND gates are preferred over others because they can be used to make any gate. This means that by using NAND gates, we can implement any logic function required in a circuit. This versatility makes NAND gates a popular choice in digital circuit design as it simplifies the overall circuit complexity and reduces the number of different gate types needed.
21.
In case of OR gate, no matter what the number of inputs, a
Correct Answer
A. 1 at any input causes the output to be at logic 1
Explanation
In an OR gate, if there is a 1 at any input, the output will be at logic 1. This is because the OR gate is designed to produce a 1 output if any of its inputs are 1. Therefore, regardless of the number of inputs, as long as there is a 1 at any input, the output will be at logic 1.
22.
The fan put of a 7400 NAND gate is
Correct Answer
D. 10TTL
Explanation
The fan-out of a NAND gate refers to the maximum number of inputs that the gate can drive without affecting its performance. In this case, the correct answer of 10TTL suggests that the fan-out of the 7400 NAND gate is 10, meaning it can drive up to 10 TTL inputs without any issues.
23.
Excess-3 code is known as
Correct Answer
C. Self-complementing code
Explanation
Excess-3 code is known as a self-complementing code because it has the property that the 9's complement of a number is equal to its 1's complement. In other words, to find the 9's complement of a number in Excess-3 code, we simply invert each digit. This property makes arithmetic operations easier to perform in this code.
24.
Assuming 8 bits for data, 1 bit for parity, I start bit and 2 stop bits, the number of characters that 1200 BPS communication line can transmit is
Correct Answer
C. 12CPS
Explanation
The given question is asking about the number of characters that a 1200 BPS communication line can transmit. BPS stands for bits per second, so it refers to the rate at which data is transmitted. In this case, the data consists of 8 bits for the actual data, 1 bit for parity, and 2 stop bits. Therefore, the total number of bits transmitted per character is 11 (8 + 1 + 2). Since the communication line has a rate of 1200 BPS, it can transmit 1200 bits per second. Dividing 1200 by 11 gives us approximately 109.09 characters per second (CPS). Rounding this down to the nearest whole number, we get 109 CPS. Therefore, the correct answer is 12 CPS.
25.
Indicate which of the following three binary additions are correct?
1.1011 + 1010 = 10101
II. 1010 + 1101 = 10111
III. 1010 + 1101 = 11111
Correct Answer
D. II only
Explanation
I. 1.1011 + 1010 = 10101
This addition is not correct. The correct result is 11001.
II. 1010 + 1101 = 10111 - This addition is correct. The result is indeed 10111.
III. 1010 + 1101 = 11111 - This addition is not correct. The correct result is 11011.
So, the correct answers are:
II. 1010 + 1101 = 10111