Common EDC Lab Viva Questions and Answers

Tricky ECE VIVA Questiions and Answers for Engineering students.

1. What is Electronic?
The study and use of electrical devices that operate by controlling the flow of electrons or other electrically charged particles.

2. What is communication?
Communication means transferring a signal from the transmitter which passes through a medium then the output is obtained at the receiver. (or)communication says as transferring of message from one place to another place called communication.

3. Different types of communications? Explain.
Analog and digital communication.
As a technology, analog is the process of taking an audio or video signal (the human voice) and translating it into electronic pulses. Digital on the other hand is breaking the signal into a binary format where the audio or video data is represented by a series of "1"s and "0"s.
Digital signals are immune to noise, quality of transmission and reception is good, components used in digital communication can be produced with high precision and power consumption is also very less when compared with analog signals.

4. What is sampling?
The process of obtaining a set of samples from a continuous function of time x(t) is referred to as sampling.

5. State sampling theorem?
It states that, while taking the samples of a continuous signal, it has to be taken care that the sampling rate is equal to or greater than twice the cut off frequency and the minimum sampling rate is known as the Nyquist rate.

6. What is cut-off frequency?
The frequency at which the response is -3dB with respect to the maximum response.

7. What is pass band?
Passband is the range of frequencies or wavelengths that can pass through a filter without being attenuated.

8. What is stop band?
A stopband is a band of frequencies, between specified limits, in which a circuit, such as a filter or telephone circuit, does not let signals through, or the attenuation is above the required stopband attenuation level.

9. Explain RF?
Radio frequency (RF) is a frequency or rate of oscillation within the range of about 3 Hz to 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves. Since most of this range is beyond the vibration rate that most mechanical systems can respond to, RF usually refers to oscillations in electrical circuits or electromagnetic radiation.

10. What is modulation? And where it is utilized?
Modulation is the process of varying some characteristic of a periodic wave with an external signals.
Radio communication superimposes this information bearing signal onto a carrier signal.
These high frequency carrier signals can be transmitted over the air easily and are capable of travelling long distances.
The characteristics (amplitude, frequency, or phase) of the carrier signal are varied in accordance with the information bearing signal.
Modulation is utilized to send an information bearing signal over long distances.

11. What is demodulation?
Demodulation is the act of removing the modulation from an analog signal to get the original baseband signal back. Demodulating is necessary because the receiver system receives a modulated signal with specific characteristics and it needs to turn it to base-band.

12. Name the modulation techniques?
For Analog modulation--AM, SSB, FM, PM and SM
Digital modulation--OOK, FSK, ASK, Psk, QAM, MSK, CPM, PPM, TCM, OFDM

13. Explain AM and FM?
AM-Amplitude modulation is a type of modulation where the amplitude of the carrier signal is varied in accordance with the information bearing signal.
FM-Frequency modulation is a type of modulation where the frequency of the carrier signal is varied in accordance with the information bearing signal.

14. Where do we use AM and FM?
AM is used for video signals for example TV. Ranges from 535 to 1705 kHz.
FM is used for audio signals for example Radio. Ranges from 88 to 108 MHz.

15. What is a base station?
Base station is a radio receiver/transmitter that serves as the hub of the local wireless network, and may also be the gateway between a wired network and the wireless network.

16. How many satellites are required to cover the earth?
3 satellites are required to cover the entire earth, which is placed at 120 degree to each other. The life span of the satellite is about 15 years.

17. What is a repeater?
A repeater is an electronic device that receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances without degradation.

18. What is an Amplifier?
An electronic device or electrical circuit that is used to boost (amplify) the power, voltage or current of an applied signal.

19. Example for negative feedback and positive feedback?
Example for –ve feedback is ---Amplifiers And for +ve feedback is – Oscillators.

20. What is Oscillator?
An oscillator is a circuit that creates a waveform output from a direct current input. The two main types of oscillator are harmonic and relaxation. The harmonic oscillators have smooth curved waveforms, while relaxation oscillators have waveforms with sharp changes.

21. What is an Integrated Circuit?
An integrated circuit (IC), also called a microchip, is an electronic circuit etched onto a silicon chip. Their main advantages are low cost, low power, high performance, and very small size.

22. What is crosstalk?
Crosstalk is a form of interference caused by signals in nearby conductors. The most common example is hearing an unwanted conversation on the telephone. Crosstalk can also occur in radios, televisions, networking equipment, and even electric guitars.

23. What is resistor?
A resistor is a two-terminal electronic component that opposes an electric current by producing a voltage drop between its terminals in proportion to the current, that is, in accordance with Ohm's law:
V = IR.

25. What is inductor?
An inductor is a passive electrical device employed in electrical circuits for its property of inductance. An inductor can take many forms.

26. What is conductor?
A substance, body, or device that readily conducts heat, electricity, sound, etc. Copper is a good conductor of electricity.

27. What is a semi conductor?
A semiconductor is a solid material that has electrical conductivity in between that of a conductor and that of an insulator(An Insulator is a material that resists the flow of electric current. It is an object intended to support or separate electrical conductors without passing current through itself); it can vary over that wide range either permanently or dynamically.

28. What is diode?
In electronics, a diode is a two-terminal device. Diodes have two active electrodes between which the signal of interest may flow, and most are used for their unidirectional current property.

29. What is transistor?
In electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals. The transistor is the fundamental building block of computers, and all other modern electronic devices. Some transistors are packaged individually but most are found in integrated circuits.

30. What is op-amp?
An operational amplifier, often called an op-amp , is a DC-coupled high-gain electronic voltage amplifier with differential inputs[1] and, usually, a single output. Typically the output of the op-amp is controlled either by negative feedback, which largely determines the magnitude of its output voltage gain, or by positive feedback, which facilitates regenerative gain and oscillation.

31. What is a feedback?
Feedback is a process whereby some proportion of the output signal of a system is passed (fed back) to the input. This is often used to control the dynamic behaviour of the system.

32. Advantages of negative feedback over positive feedback?
Much attention has been given by researchers to negative feedback processes, because negative feedback processes lead systems towards equilibrium states. Positive feedback reinforces a given tendency of a system and can lead a system away from equilibrium states, possibly causing quite unexpected results.

33. What is Barkhausen criteria?
Barkhausen criteria, without which you will not know which conditions, are to be satisfied for oscillations.
“Oscillations will not be sustained if, at the oscillator frequency, the magnitude of the product of the
transfer gain of the amplifier and the magnitude of the feedback factor of the feedback network ( the magnitude of the loop gain ) are less than unity”.
The condition of unity loop gain -Aβ = 1 is called the Barkhausen criterion. This condition implies that
Aβ= 1and that the phase of - Aβ is zero.

34. What is CDMA, TDMA, FDMA?
Code division multiple access (CDMA) is a channel access method utilized by various radio communication technologies. CDMA employs spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code) to allow multiple users to be multiplexed over the same physical channel. By contrast, time division multiple access (TDMA) divides access by time, while frequency-division multiple access (FDMA) divides it by frequency.
An analogy to the problem of multiple access is a room (channel) in which people wish to communicate with each other. To avoid confusion, people could take turns speaking (time division), speak at different pitches (frequency division), or speak in different directions (spatial division). In CDMA, they would speak different languages. People speaking the same language can understand each other, but not other people. Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only users associated with a particular code can understand each other.

35. explain different types of feedback?
Types of feedback:
Negative feedback: This tends to reduce output (but in amplifiers, stabilizes and linearizes operation). Negative feedback feeds part of a system's output, inverted, into the system's input; generally with the result that fluctuations are attenuated.
Positive feedback: This tends to increase output. Positive feedback, sometimes referred to as "cumulative causation", is a feedback loop system in which the system responds to perturbation (A perturbation means a system, is an alteration of function, induced by external or internal mechanisms) in the same direction as the perturbation. In contrast, a system that responds to the perturbation in the opposite direction is called a negative feedback system.
Bipolar feedback: which can either increase or decrease output.

36. What are the main divisions of power system?
The generating system,transmission system,and distribution system.

37. What is Instrumentation Amplifier (IA) and what are all the advantages?
An instrumentation amplifier is a differential op-amp circuit providing high input impedances with ease of gain adjustment by varying a single resistor.

38. What is meant by impedance diagram? 
The equivalent circuit of all the components of the power system are drawn and they are interconnected is called impedance diagram.

39. What is the need for load flow study?
The load flow study of a power system is essential to decide the best operation existing system and for planning the future expansion of the system. It is also essential for designing the power system.

40. What is the need for base values? 
The components of power system may operate at different voltage and power levels. It will be convenient for analysis of power system if the voltage, power, current ratings of the components of the power system is expressed with referance to a common value called base value.

Hirred Embedded Systems based Viva Questions and Answers

Frequently Asked Embedded Systems viva questions with answers:

Q1. What is an embedded system?
Ans. An embedded system is a special purpose computer system which is completely encapsulated by device it control. It is a programmed hardware device in which the hardware chip is programmed with specific function. It is a combination of hardware and software.

Q2. What are the characteristics of embedded system? 
Ans. The Characteristics of the embedded systems are as follows-
1. Sophisticated functionality
2. Real time behavior
3. Low manufacturing cost
4. Low power consumption
5. User friendly
6. Small size

Q3. What are the types of embedded system? 
Ans. They are of 4 types
1. General computing
2. Control System
3. Digital Signal Processing
4. Communication and network

Q4. What is digital signal controller ?
Ans. DSC is 16 bit RISC machine that combines control advantages of micro-controller and digital signal processing to produce tightly coupled single chip-single instruction stream solution for embedded system design.

Q5. What are the components of embedded system?
Ans. Microcontroller, microprocessor, DSC, DSP, busses, system clock, Read only Memory(ROM), RAM, Real time clock these are the components of embedded system.

Q6. Why we use embedded systems?
Ans. Embedded systems avoid lots of electronic components and they have rich built in functionality. They reduces the cost and maintenance cost and the probability of failure of embedded system is less so embedded system are in very much use now a days.

Q7. What are the languages used in embedded system?
Ans. Assembly language and C are  basically used for embedded system. Java and ADA are also preferred.

Q8. How does combination of functions reduce memory requirement in embedded system?
Ans. By using functions the amount of code that has to be dealt with is reduced thus redundancy is eliminated for everything common in function.

Q9. What is the significance of watchdog timer in ES?
Ans. It is a timing device which is set to predefined time interval and some task is to be performed at that time. It is used to reset original state when an inappropriate event take place.It is usually operated by counter device.

Q10. What is the difference between mutexes and semaphores?
Ans. Semaphores are the synchronization tool to overcome critical section problem.
Mutex is also a tool that is used to provide deadlock free mutual exclusion. It protects access to every critical data item, if the data is locked and is in use,it either waits for the thread to finish or awakened to release the lock from its inactive state.

Q11. What is the difference between FIFO and the memory?
FIFO (first in first out) is a memory structure where data’s can be stored and retrieved. This is a queue where memory is a storage device which can hold data’s dynamically or at any desired locations and can be retrieved in any order.

Q12. What is an anti-aliasing filter?
Anti-aliasing filter reduces errors due to aliasing.

Q13. How to implement a fourth order Butter worth LP filter at 1 KHz if sampling frequency is 8 KHz?
A fourth order butter worth filter can be made as cascade of two second order LP filters with zeta of 0.924 and 0.383. One can use a bilinear transformation approach for realising second order LP filters. Using this technique described well in many texts, one can make second order LP filters and cascade them

Q14. Is 8085 an embedded system?
It’s not an embedded system. B’coz it will be a part of an embedded system and it does not work on any software.

 Q15.What is the role of segment register?
In the 8086 processor architecture, memory addresses are specified in two parts called the segment and the offset. Segment values are stored in the segment registers. There are four or more segment registers: Code Segment (CS) contains segment of the current instruction (IP is the offset), Stack segment (SS) contain stack of the segment (SP is the offset), DS is the segment used by default for most data operations; ES is an extra segment register.

Q16.What type of registers contains an INTEL CPU?
 Special function registers like accumulator, program controller (PC), data pointer (DPTR), TMOD and TCON (timing registers), 3 register banks with r0 to r7, Bit addressable registers like B.

 Q17. What is the difference between microprocessor and micro controller?
Microprocessor is managers of the resources (I/O, memory) which lie out-side of its architecture.
Micro controllers have I/O, memory etc. built into it and specifically designed for control.

Q18. DMA deals with which address (physical/virtual addresses)?
DMA deals with physical addresses. DMA controller is a device which directly drives the data and address bus during data transfer. So it is purely physical address.

 Q19. What is the difference between testing and verification?
Verification is a front end process and testing is a post silicon process. Verification is to verify the functionality of the design during the design cycle. Testing is find manufacturing faults.

Recently Asked Microprocessors and Microcontroller Lab viva Questions with Answers

Most Recently Asked MPMC Viva Questions with Answers:

1.What is a Microprocessor?
Microprocessor is a CPU fabricated on a single chip, program-controlled device, which fetches the instructions from memory, decodes and executes the instructions.

2. What is Instruction Set?
 It is the set of the instructions that the Microprocessor can execute.

3. What is Bandwidth ?
 The number of bits processed by the processor in a single instruction.

4. What is Clock Speed ?
Clock speed is measured in the MHz and it determines that how many instructions a processor can processed.The speed of the microprocessor is measured in the MHz or GHz.

5. What are the features of Intel 8086 ?
Features:
·  Released by Intel in 1978
·  Produced from 1978 to 1990s
·  A 16-bit microprocessor chip.
·  Max. CPU clock rate:5 MHz to 10 MHz
·  Instruction set:  x86-16
·  Package: 40 pin DIP
·  16-bit Arithmetic Logic Unit
·  16-bit data bus  (8088 has 8-bit data bus)
·  20-bit address bus - 220 = 1,048,576 = 1 meg
·  The address refers to a byte in memory.

6.What are the flags in 8086?
In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.

7.Why crystal is a preferred clock source?
Because of high stability, large Q (Quality Factor) & the frequency that doesn’t drift with aging. Crystal is used as a clock source most of the times.

8.What is Tri-state logic?
Three Logic Levels are used and they are High, Low, High impedance state. The high and low are normal logic levels & high impedance state is electrical open circuit conditions. Tri-state logic has a third line called enable line.

9.What happens when HLT instruction is executed in processor?
The Micro Processor enters into Halt-State and the buses are tri-stated.

10.What is Program counter?
Program counter holds the address of either the first byte of the next instruction to be fetched for execution or the address of the next byte of a multi byte instruction, which has not been completely fetched. In both the cases it gets incremented automatically one by one as the instruction bytes get fetched. Also Program register keeps the address of the next instruction.

11.What is 1st / 2nd / 3rd / 4th generation processor?
The processor made of PMOS / NMOS / HMOS / HCMOS technology is called 1st / 2nd / 3rd / 4th generation processor, and it is made up of 4 / 8 / 16 / 32 bits.

12.What is the Maximum clock frequency in 8086?
5 Mhz is the Maximum clock frequency in 8086.

13.What is meant by Maskable interrupts?
An interrupt that can be turned off by the programmer is known as Maskable interrupt.

14.What is Non-Maskable interrupts?
An interrupt which can be never be turned off (ie. disabled) is known as Non-Maskable interrupt

15.What are the different functional units in 8086?
Bus Interface Unit and Execution unit, are the two different functional units in 8086.

16.What are the various segment registers in 8086?
Code, Data, Stack, Extra Segment registers in 8086.

17.What does EU do?
Execution Unit receives program instruction codes and data from BIU, executes these instructions and store the result in general registers.

18.Which Stack is used in 8086? k is used in 8086?
FIFO (First In First Out) stack is used in 8086.In this type of Stack the first stored information is retrieved first.

19.What are the flags in 8086?
In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.

20.What is SIM and RIM instructions?
SIM is Set Interrupt Mask. Used to mask the hardware interrupts.
RIM is Read Interrupt Mask. Used to check whether the interrupt is Masked or not.

21.What are Flag registers?
A:-Divided into 2 parts:-Condition code or status flags and machine control flags.
S-Sign Flag:-Is to set when the result of any computation is negative.
Z-Zero Flag:-Is to set if the result of the computation or comparison performed by the previous instruction is zero.
C-Carry Flag:-Is set when there is carry out of MSB in case of addition or a borrow in case of subtraction.
T-Trap Flag:-Is set,the processor enters the single step execution mode.
I-Interrupt Flag:-Is set,the maskable interrupts are recognized by the CPU.
D-Direction Flag:-Is set for autoincrementing or autodecrementing mode in string manipulation instructions.
AC-Auxiliary Carry Flag:-Is set if there is a carry from the lowest nibble during addition or borrow for the lowest nibble.
O-Overflow Flag:-Is setif the result of a signed operation is large enough to be accommodated in a destination register.

22.Write the flags of 8086?
The 8086 has nine flags and they are
1. Carry Flag (CF)                6. Overflow Flag (OF)
2. Parity Flag (PF)                 7. Trace Flag (TF)
3. Auxiliary carry Flag (AF)   8. Interrupt Flag (IF)
4. Zero Flag (ZF)                  9. Direction Flag (DF)
5. Sign Flag (SF)

23. What are the interrupts of 8086?
The interrupts of 8085 are INTR and NMI. The INTR is general maskable interrupt and NMI is non-maskable interrupt.

24. How clock signal is generated in 8086? What is the maximum internal clock frequency of 8086?
The 8086 does not have on-chip clock generation circuit. Hence the clock generator chip, 8284 is connected to the CLK pin of8086. The clock signal supplied by 8284 is divided by three for internal use. The maximum internal clock frequency of8086 is 5MHz.

25. Write the special functions carried by the general purpose registers of 8086?
The special functions carried by the registers of 8086 are the following.
Register Special function
1. AX 16-bit Accumulator
2. AL 8-bit Accumulator
3. BX Base Register 4. CX Count Register 5. DX .Data Register

26.What is the need for Port?
The I/O devices are generally slow devices and their timing characteristics do not match with processor timings. Hence the I/O devices are connected to system bus through the ports.

27.What is a port?
The port is a buffered I/O, which is used to hold the data transmitted from the microprocessor to I/O device or vice-versa.

28.What is processor cycle (Machine cycle)?
The processor cycle or machine cycle is the basic operation performed by the processor. To execute an instruction, the processor will run one or more machine cycles in a particular order.

29.What is Instruction cycle?
The sequence of operations that a processor has to carry out while executing the instruction is called Instruction cycle. Each instruction cycle of a processor indium consists of a number of machine cycles.

30.What is fetch and execute cycle?
In general, the instruction cycle of an instruction can be divided into fetch and execute cycles. The fetch cycle is executed to fetch the opcode from memory. The execute cycle is executed to decode theinstruction and to perform the work instructed by the instruction.

Top 10 MICROWAVE ENGINEERING LAB VIVA QUESTIONS AND ANSWERS

Latest Microwave Engineering VIVA Questions and Answers:

1. What is Microwave Engineering?
Ans. Microwave engineering is the study and design of microwave circuits , components , and systems. Fundamental principles are applied to analysis , design and measurement techniin this field.The short wavelengths involved distinguish this discipline from electronic engineering . This is because there are different interactions with circuits, transmissions and propagation characteristics at microwave frequencies.a

2. Define s-matrix and its properties?
Ans. In a microwave junction there is an interaction of three or more components.There will be an output port, in addition there may be reflection from the junction of other ports. Totally there may be many combination, these are represented easily using a matrix called S matrix.
Properties of s- matrix
1. it possess symmetric properties sij=sji
2. it possess unitary property
3. [s][s]*=[i]

3. Write the applications of microwave engineering?
Ans. Following are the applications of microwave engineering-
1. Antenna gain is proportional to the electrical size of the antenna. At higher frequencies, more antenna gain is therefore possible for a given physical antenna size, which has important consequences for implementing miniaturized microwave systems.
2. More bandwidth can be realized at higher frequencies. Bandwidth is critically important because available frequency bands in the electromagnetic spectrum are being rapidly depleted.
3. Microwave signals travel by line of sight are not bent by the ionosphere as are lower frequency
signals and thus satellite and terrestrial communication links with very high capacities are possible.

4. Why is s-matrix used in MW analysis?
Ans. Matrix is used in MW analysis to overcome the problem which occurs when H,Y & Z parameter are used in high frequencies.

5. What are the advantages of ABCD matrix?
Ans. The advantages of ABCD matrix are as follows-
1. They are used in power transmission lines
2. They are helpful in case of cascade networks.

6. What are junctions ? Give some example
 Ans. A microwave circuit consists of several microwave devices connected in some way to achieve the desired transmission of MW signal. The interconnection of two or more microwave may be regarded as MW junction.
E.g.: TEE, HYBRID RING

7. What are non-reciprocal devices ?Give two examples?
Ans. The devices which are having the properties that the forward characteristics are not equal to the reverse characteristics are called non-reciprocal devices.

8. What are the applications of reflex klystron?
Ans. The main applications of a reflex klystron are as follows-
1. Signal source in MW generator
2. Local oscillators in receivers
3. It is used in FM oscillator in low power MW links.
4. In parametric amplifier as pump source.

9. What is the purpose of slow wave structures used in TWT amplifiers?
Ans. Slow wave structures are special circuits that are used in microwave tubes to reduce wave velocity in a certain direction so that the electron beam and the signal wave can interact. In TWT, since the beam can be accelerated only to velocities that are about a fraction of the velocity of light, slow wave structures are used.

10.Give two examples for two port junctions?
Ans. Following are the two examples of two port junctions-
1. The junction of two rectangular guides of unequal height
2. A symmetrical junction consisting of two similar rectangular guides joined by an Intermediate guide of greater width.

Recently Asked Digital image processing Viva Questions and Answers

Latest Digital image processing Viva Questions and Answers :

1. Define Image?
An image may be defined as two dimensional light intensity function f(x, y) where x and y denote spatial co-ordinate and the amplitude or value of f at any point (x, y) is called intensity or gray scale or brightness of the image at that point.

2. What is Dynamic Range?
The range of values spanned by the gray scale is called dynamic range of an image. Image will have high contrast, if the dynamic range is high and image will have dull washed out gray look if the dynamic range is low.

3. Define Brightness?
Brightness of an object is the perceived luminance of the surround. Two objects with different surroundings would have identical luminance but different brightness.

4. What do you meant by Gray level?
Gray level refers to a scalar measure of intensity that ranges from black to grays and finally to white.

5. What do you meant by Color model?
A Color model is a specification of 3D-coordinates system and a subspace within that system where each color is represented by a single point.

6. List the hardware oriented color models?
1. RGB model
2. CMY model
3. YIQ model
4. HSI model

7. What is Hue and saturation?
Hue is a color attribute that describes a pure color where saturation gives a measure of the degree to which a pure color is diluted by white light.

8. List the applications of color models?
1. RGB model--- used for color monitors & color video camera
2. CMY model---used for color printing
3. HIS model----used for color image processing
4. YIQ model---used for color picture transmission

9. What is Chromatic Adoption?
The hue of a perceived color depends on the adoption of the viewer. For example,the American Flag will not immediately appear red, white, and blue of the viewer has been subjected to high intensity red light before viewing the flag. The color of the flag will appear to shift in hue toward the red component cyan.

10. Define Resolutions? 
Resolution is defined as the smallest number of discernible detail in an image.Spatial resolution is the smallest discernible detail in an image and gray level resolution refers to the smallest discernible change is gray level.

11. What is meant by pixel?
A digital image is composed of a finite number of elements each of which has a particular location or value. These elements are referred to as pixels or image elements or picture elements or pixls elements.

12. Define Digital image? 
When x, y and the amplitude values of f all are finite discrete quantities , we call the image digital image.

13. What are the steps involved in DIP?
1. Image Acquisition
2. Preprocessing
3. Segmentation
4. Representation and Description
5. Recognition and Interpretation

14. What is recognition and Interpretation?
Recognition means is a process that assigns a label to an object based on the information provided by its descriptors.Interpretation means assigning meaning to a recognized object.

15. Specify the elements of DIP system?
1. Image Acquisition
2. Storage
3. Processing
4. Display

16. List the categories of digital storage?
1. Short term storage for use during processing.
2. Online storage for relatively fast recall.
3. Archival storage for infrequent access.

17. What are the types of light receptors?
The two types of light receptors are
• Cones and
• Rods

18. Differentiate photopic and scotopic vision ?
Photopic vision Scotopic vision
1. The human being can resolve the fine details with these cones because each one is connected to its own nerve end.
2. This is also known as bright light vision.

19. How cones and rods are distributed in retina?
In each eye, cones are in the range 6-7 million and rods are in the range 75-150 million.

20. Define subjective brightness and brightness adaptation?
Subjective brightness means intensity as preserved by the human visual system.Brightness adaptation means the human visual system can operate only from scotopic to glare limit. It cannot operate over the range simultaneously. It accomplishes this large variation by changes in its overall intensity.

21. Define weber ratio?
The ratio of increment of illumination to background of illumination is called as web er ratio.(ie) Δi/i
If the ratio (Δi/i) is small, then small percentage of change in intensity is needed (ie) good brightness adaptation.
If the ratio (Δi/i) is large , then large percentage of change in intensity is needed (ie) poor brightness adaptation.

22. What is meant by mach band effect?
Mach band effect means the intensity of the stripes is constant. Therefore it preserves the brightness pattern near the boundaries, these bands are called as mach band effect.

23. What is simultaneous contrast?
The region reserved brightness not depend on its intensity but also on its background. All centre square have same intensity. However they appear to the eye to become darker as the background becomes lighter.

24. What is meant by illumination and reflectance?
Illumination is the amount of source light incident on the scene. It is represented as i(x, y).
Reflectance is the amount of light reflected by the object in the scene. It is represented by r(x, y).

26. Define sampling and quantization?
Sampling means digitizing the co-ordinate value (x, y).Quantization means digitizing the amplitude value. Several rods are connected to one nerve end. So it gives the overall picture of the image.This is also known as thin lightvision.

Top 30 C LANGUAGE VIVA QUESTIONS AND ANSWERS

Tricky C Language VIVA Questions with Answers:

1)Who invented C Language?
Dennis Ritchie in 1972 developed a new language by inheriting the features of both BCPL and B and adding additional features. He named the language as just C.

2) Who invented B Language?
Ken Thomson at AT&T Bell Labs developed a language and named it B. Even the B language was found to have some short comings to support development of both business applications and system software.

3) Who invented BCPL Language?
Basic Combined Programming Language(BCPL) was developed by Martin Richards, Cambridge university.

4) Why C Language?
C is one of the high level languages. It is a general purpose language, which means it can be used to write programs of any sort.

5) What are the features of C Langauges?
In C one can write programs like that of high level languages as in COBOL, BASIC, FORTRAN etc. as well as it permits very close interaction with the inner workings of the computer.
It is a general purpose programming language. It is usually called system programming language but equally suited to writing a variety of applications.
It supports various data types.
It follows the programming style based on fundamental control flow constructions for structured programming.
Functions may be pre–defined or user defined and they may return values of basic types, structures, unions or pointers.

 6)What are the advantages of c language?
Easy to write
Rich set of operators and functions that are built–in
Support for bit–wise operation
Flexible use of pointers
Direct control over the hardware
Ability to access BIOS/DOS routines
Interacting using Interrupts
Ability to write TSR programs
Ability to create .COM files
Ability to create library files (.LIB)
Ability to write interface programs
Incorporating assembly language in C program

7) What are the disadvantages of c langauge?
C is considered difficult to learn
Because of its conciseness, the code can be difficult to follow
It is not suited to applications that require a lot of report formatting and data file manipulation.

 8) What are the salient features of c languages?
The following are the salient features of C language are :
C is called a middle level language
C supports structured design approach
C is extensible
C is rich in data types and operators
C is portable

 9) What is a header file?
Header files provide the definitions and declarations for the library functions. Thus, each header file contains the library functions along with the necessary definitions and declarations. For example, stdio.h, math.h, stdlib.h, string.h etc.

10) What is character set?
Character set is the set of characters allowed and supported in the programming language. Generally a program is a collection of instructions, which contain groups of characters. Only a limited set of characters is allowed to write instructions in the program.

11) What is C token?
The smallest individual units of a C program are known as tokens.

12) List the different types of C tokens?
Constants
Identifiers
Keywords
Operators
Special symbols
Strings

13) What is a string?
A string is a sequence of characters ending with NUL. It can be treated as a one–dimensional array of characters terminated by a NUL character.

14) What are qualifiers?
Qualifiers or modifiers are identifiers that may precede the scalar data types (except float) to specify the number of bits used for representing the respective type of data in memory. The qualifiers in C are short, long, signed, and unsigned.

15) What is a function?
A function is a set of statements to perform a specific task.

16) What is a constant?
A constant is a value that does not change during the program execution. A constant used in C does not occupy memory.

17) What are the different types of constants?
There are five types of constants. They are :
Integer constants
Floating point constants
Character constants
String literals
Enumeration constants

18) What is variable?
An identifier is used to identify and store some value. If the value of the identifier is changed during the execution of the program, then the identifier is known as variable.

19) What are the rules for the identifier?
The first character must be an alphabet or underscore (_)
Digits may be included in the variable
The maximum number of characters in a word are 32 (It may vary depending upon the platform)
No other special characters are allowed.

 20) What are global variables?
Global Variables are those, which are required to be acccessed by all the functions defined after their declaration. So, the variables declared before the main {) can be acccessed by all the functions, which follow their declaration.

21) What is a keyword?
Keywords are those words of C which have predefined meaning assigned by the C language. They form a part of the database required by the C compiler.

22) What are the different types of c instructions?
There are basically three types of instructions in C are :
Type Declaration Instruction
Arithmetic Instruction
Control Instruction

 23) What is an expression?
Expression is defined as a combination of operands and operators to obtain some computation. Operands represent variables or values and The operator tells is what operation to be performed.

24) What are the types of data files?
There are two types of data files :
stream oriented or standard data files
system oriented or low level data files

 25) Why C is called a middle level language?
C combines the features of both Assembly Level Languages (Low Level Languages) and Higher Level Languages. For this reason, C is referred to as a Middle Level Language. The feature of ALLs is that of enabling us to develop system level programs and the features of HLLs are those of higher degree of readability and machine independence.

26) How can variables be characterized?
The variables can be categorized by storage class as well as by data type. The storage class specifies the portion of the program within which the variables are recognized.

27) Give the rules for variable declaration?
The rules for variable declaration in C are given below :
A variable name consists of alphabets, digits and the underscore (_) character
The length of variable should be kept upto 8 characters though your system may allow upto 40 characters
They must begin with an alphabet
Some systems also recognize an underscore as the first character
White space and commas are not allowed
Any reserved word (keyword) cannot be used as a variable name.

28) What is the purpose of type declarations?
The type declaration allow to create a synonym for other data types. Its syntax is type def type identifier; The declaration type def unsigned long int INTEGER

29) What is recursion?
C language a function may call another function. When a function calls itself, it is referred to as recursive call and the process is known as recursion. C provides very good facilities for recursion.

30) What is data types?
Data types refer to the classes of data that can be manipulated by C programs. The three fundamental data types supported by C are character, integer and real type.

Commonly Asked Java Programming VIVA Questions and Answers

Top 30 Viva Questions & Answers for Java Developers:

1.What is JVM?
The Java interpreter along with the run time environment required to run the Java application in called as Java virtual machine(JVM)

 2. What is the most important feature of Java?
Java is a platform independent language.

3. What do you mean by platform independence?
Platform independence means that we can write and compile the java code in one platform (eg Windows) and can execute the class in any other supported platform eg (Linux,Solaris,etc).

 4. What is the difference between a JDK and a JVM?
JDK is Java Development Kit which is for development purpose and it includes execution environment also. But JVM is purely a run time environment and hence you will not be able to compile your source files using a JVM.

5. What is the base class of all classes?
java.lang.Object

 6. What are the access modifiers in Java?
There are 3 access modifiers. Public, protected and private, and the default one if no identifier is specified is called friendly, but programmer cannot specify the friendly identifier explicitly.

 7. What is are packages?
 A package is a collection of related classes and interfaces providing access protection and namespace   management.

 8. What is meant by Inheritance and what are its advantages?
 Inheritance is the process of inheriting all the features from a class. The advantages of inheritance are reusability  of code and accessibility of variables and methods of the super class by sub classes.

 9. What is the difference between superclass and subclass?
 A super class is a class that is inherited whereas sub class is a class that does the inheriting.

 10. What is an abstract class?
 An abstract class is a class designed with implementation gaps for sub classes to fill in and is deliberately  incomplete.

 11. What are the states associated in the thread?
 Thread contains ready, running, waiting and dead states.

 12. What is synchronization?
 Synchronization is the mechanism that ensures that only one thread is accessed the resources at a time.

 13. What is deadlock?
 When two threads are waiting each other and can’t precede the program is said to be deadlock.

 14. What is an applet?
 Applet is a dynamic and interactive program that runs inside a web page displayed by a java capable browser

 15. What is the lifecycle of an applet?
init() method - Can be called when an applet is first loaded
start() method - Can be called each time an applet is started.
paint() method - Can be called when the applet is minimized or maximized.
stop() method - Can be used when the browser moves off the applet’s page.
destroy() method - Can be called when the browser is finished with the applet.


 16. How do you set security in applets?
  using setSecurity Manager() method

 17. What is a layout manager and what are different types of layout managers available in java AWT?
 A layout manager is an object that is used to organize components in a container. The different layouts are    available are FlowLayout, BorderLayout, CardLayout, GridLayout and GridBagLayout

 18. What is JDBC?
 JDBC is a set of Java API for executing SQL statements. This API consists of a set of classes and interfaces to  enable programs to write pure Java Database applications.

 19. What are drivers available?
 a) JDBC-ODBC Bridge driver b) Native API Partly-Java driver
 c) JDBC-Net Pure Java driver d) Native-Protocol Pure Java driver

 20. What is stored procedure?
Stored procedure is a group of SQL statements that forms a logical unit and performs a particular task. Stored Procedures are used to encapsulate a set of operations or queries to execute on database. Stored procedures can be compiled and executed with different parameters and results and may have any combination of input/output parameters.

 21. What is the Java API?
The Java API is a large collection of ready-made software components that provide many useful capabilities, such as graphical user interface (GUI) widgets.

 22. Why there are no global variables in Java?
Global variables are globally accessible. Java does not support globally accessible variables due to following reasons:
1)The global variables breaks the referential transparency
2)Global variables creates collisions in namespace.

 23. What are Encapsulation, Inheritance and Polymorphism?
 Encapsulation is the mechanism that binds together code and data it manipulates and keeps both safe from outside interference and misuse. Inheritance is the process by which one object acquires the properties of another object. Polymorphism is the feature that allows one interface to be used for general class actions.

 24. What is the use of bin and lib in JDK?
Bin contains all tools such as javac, appletviewer, awt tool, etc., whereas lib contains API and all packages.

 25. What is method overloading and method overriding?
Method overloading: When a method in a class having the same method name with different arguments is said to be method overloading. Method overriding : When a method in a class having the same method name with same arguments is said to be method overriding.

 26. What is the difference between this() and super()?
this() can be used to invoke a constructor of the same class whereas super() can be used to invoke a super class constructor.

 27. What is Domain Naming Service(DNS)?
It is very difficult to remember a set of numbers(IP address) to connect to the Internet. The Domain Naming Service(DNS) is used to overcome this problem. It maps one particular IP address to a string of characters. For example, www. mascom. com implies com is the domain name reserved for US commercial sites, moscom is the name of the company and www is the name of the specific computer, which is mascom’s server.

 28. What is URL?
URL stands for Uniform Resource Locator and it points to resource files on the Internet. URL has four components: http://www. address. com:80/index.html, where http - protocol name, address - IP address or host name, 80 - port number and index.html - file path.

 29. What is RMI and steps involved in developing an RMI object?
Remote Method Invocation (RMI) allows java object that executes on one machine and to invoke the method of a Java object to execute on another machine. The steps involved in developing an RMI object are: a) Define the interfaces b) Implementing these interfaces c) Compile the interfaces and their implementations with the java compiler d) Compile the server implementation with RMI compiler e) Run the RMI registry f) Run the application.

30. What is RMI architecture?
RMI architecture consists of four layers and each layer performs specific functions: a) Application layer - contains the actual object definition. b) Proxy layer - consists of stub and skeleton. c) Remote Reference layer - gets the stream of bytes from the transport layer and sends it to the proxy layer. d) Transportation layer - responsible for handling the actual machine-to-machine communication.