What You Need To Know

# Top Digital System Questions And Answers – Intro to Digital Systems  This system is part of electrical engineering which have digital circuits with two well-defined state. Information about circuits signals are in binary form. Application of digital system circuits are on wide range such as our daily-life uses appliances, video games, phone, office automation, computers having wide range of capabilities.

Computer is the best example of digital system device. Digital system devices give optimum accuracy in results and faster workings but this system is complex or we can say that more complex system. To present on the basis of implementation of digital system by a network of similar components. Specification of this system divides in three part: High-Level, Binary-Level, and Algorithmic-level. It gives discrete value of signals.

1. What are the main areas where computers can replace human workers? Do you think computers will increase unemployment? Justify your answer.

Some areas are

1. Transportation
2. Agricultural Sectors
3. Manufacturing Sectors

2. How are floating point numbers represented? Explain with an example.

Floating-point representation is an alternative technique based on scientific notation. For example, the number `55.66` can be represented as `5.566×101``0.5566×102``0.05566×103`, and so on. The fractional part can be normalized. In the normalized form, there is only a single non-zero digit before the radix point. For example, decimal number `123.4567` can be normalized as `1.234567×102`; binary number `1010.1011B` can be normalized as `1.0101011B×23`.

3. Explain the terms underflow and overflow

An underflow is condition or exception that is generated when a calculation or computer operation results in a number that is smaller than what is capable of being shown and overflow is also a condition that occurs when a calculation produces a result that is greater in magnitude than that which a given register or storage location can store or represent.

4. What are synchronous counter? Explain a 3-bit synchronous counter.

A synchronous counter is a synchronous sequential circuit. In synchronous counter, all flips-flops are under the control of the same clock pulse. Also, the clock inputs of all flip-flops are connected together and are triggered by the input pulses.

3-bit synchronous counter

The J and K inputs of FF0 are connected to HIGH. FF1 has its J and K inputs connected to the output of FF0, and the J and K inputs of FF2 are connected to the output of an AND gate that is fed by the outputs of FF0 and FF1. Both FF0 and FF1 are HIGH. The positive edge of the 4th clock will cause FF2 to change its state due to the AND gate.

5. Explain the importance of flip flops in digitals systems.

Basically, flip flops are building blocks of sequential logic circuits and sequential logic circuits depends on the past output system. So they require a memory element to store the past outputs. For this purpose, flip-flops are used. Therefore, flip-flops are used in sequential circuits used to store past output of a system.

6. What is half adder and full adder? Explain with the help of circuit diagram and its truth table.

Half Adder: Half adder is a logic circuit that accepts two binary digits on its inputs and produces two binary digit outputs, a sum bit and a carry bit. The circuit diagram for half adder is below:

The truth table for half adder is below:

 Input Output A B Sum bit Carry bit 0 0 0 0
 0 1 1 0 1 0 1 0 1 1 0 1

Full adder accepts two input bits and an input carry and generates a sum output and an output carry. The circuit diagram for full adder is represented below:

The truth table for the full adder is below:

 Input Output An Bn Cn-1 Sum Sn Carry Cn 0 0 0 0 0 0 0 1 1 0 0 1 0 1 0 0 1 1 0 1 1 0 0 1 0 1 0 1 0 1
 1 1 0 0 1 1 1 1 1 1

7. What are some operations performed by ALU? Explain

• Fixed Point Operations.
Fixed-point arithmetic operations are performed on integral or whole numbers where the binary point is assumed to be to the right of the least significant bit (bit 0). For example, if we have an 8-bit register, we may express integer decimal numbers between 0 and 28minus 1 (or 255), by converting the decimal number to its binary equivalent. If we have a 16-bit register, we can store integer decimal numbers between 0 and 216minus 1 (or 65535).
• Floating Point Operations.
Floating-point operations are used to simplify the addition, subtraction, multiplication, and division of fractional numbers. They are used when dealing with fractional numbers, such as 5.724 or a very large number and signed fractional numbers. When performing arithmetic operations involving fractions or very large numbers, it is necessary to know the location of the binary (radix) point and to properly align this point before the arithmetic operation. For floating-point operations, the location of the binary point will depend on the format of the computer. All numbers are placed in this format before the arithmetic operation. The fractional portion of the number is called the mantissa and the whole integer portion, indicating the scaled factor or exponent, is called the characteristic.

8. Differentiate between register reference and memory reference instructions. Give an example of each type.

Memory reference instructions are set of instructions that have one or more of its operand addresses referring to a location in memory, as opposed to one of the CPU registers or some other way of specifying an operand and register reference instructions are also those which refer registers instead of some memory address or memory location for data to perform on. Examples are: for register reference instructions, we have instructions such as SZE, SZA, CMA, SNA, SPA, INC, CIL, CIR, CME, CLE, CLA, HLT and for memory reference instructions, we also have instructions such as AND to AC, ADD TO AC, LOAD TO AC, STORE AC, BUN, BSA.

9. What are the merits of DVD ROMs over CD ROMs?

1. DVD ROMs offers the ability to manage content and control user experience and also involve the audience.
2. DVD ROMs use a higher sampling rate and can store more information
3. It produces a richer, fuller sound and delivers a video image that’s twice as clear as VHS
4. It also offers copy protection and a lockout feature to prevent unauthorized access
5. Unlike CD-ROM, DVD doesn’t degrade each time it is played, so the life expectancy is indefinite

10. What is a computer bus? How are they useful in a pc? 