Interview Questions.

Top 100+ Linux Embedded Systems Interview Questions And Answers

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Top 100+ Linux Embedded Systems Interview Questions And Answers

Question 1. Explain What Is Embedded System In A Computer System?

Answer :

An embedded device is a pc device that is part of a bigger gadget or device.  It is a system with a committed function within a bigger electric or mechanical system.

Question 2. Mention What Are The Essential Components Of Embedded System?

Answer :

Essential components of embedded machine includes
•Hardware
•Processor
•Memory
•Timers
•I/O circuits
•System application precise circuits
•Software
•It ensures the provision of System Memory
•It tests the Processor Speed availability
•The want to restriction power lost when strolling the system continuously
•Real Time Operating System
•It runs a method as per scheduling and do the switching from one technique to another

Red Hat Linux Essentials Interview Questions
Question three. Why Embedded System Is Useful?

Answer :

With embedded machine, it is possible to update dozens or even more of hardware common sense gates, enter buffers, timing circuits, output drivers, and so forth. With a noticeably cheap microprocessor.

Question 4. Explain What Are Real-time Embedded Systems?

Answer :

Real-time embedded structures are computer systems that display, respond or control an outside surroundings. This environment is hooked up to the computer gadget thru actuators, sensors, and other input-output interfaces.

Linux Embedded structures Tutorial
Question five. Explain What Is Microcontroller?

Answer :

The microcontroller is a self-contained gadget with peripherals, memory and a processor that may be used as embedded device.

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Question 6. Mention What Is The Difference Between Microprocessor And Microcontroller?

Answer :

Microprocessor is managers of the resources (I/O, memory) which lie outside of its architecture Microcontroller have I/O, memory, and many others. Built into it and in particular designed for manipulate.

Question 7. What Does Dma Address Will Deal With?

Answer :

DMA address offers with physical addresses. It is a tool which immediately drives the facts and address bus during data transfer. So, it is in basic terms physical cope with.

Unix/Linux Tutorial Ubuntu Certified Professional Interview Questions
Question 8. Explain What Is Interrupt Latency? How Can You Reduce It?

Answer :

Interrupt latency is a time taken to go back from the interrupt carrier recurring post coping with a selected interrupt.  By writing minor ISR routines, interrupt latency may be decreased.

Question nine. Mention What Are Buses Used For Communication In Embedded System?

Answer :

For embedded gadget, the buses used for verbal exchange includes

• I2C: It is used for communique between more than one ICs
• CAN: It is utilized in cars with centrally managed community
• USB: It is used for verbal exchange among CPU and devices like mouse, and so forth.

While ISA, EISA, PCI are popular buses for parallel communication used in PCs, computer network gadgets, and so forth.

IBM AIX Interview Questions
Question 10. List Out Various Uses Of Timers In Embedded System?

Answer :

Timers in embedded system are utilized in a couple of methods

• Real Time Clock (RTC) for the device
• Initiating an occasion after a preset time put off
• Initiating a good after a contrast of preset instances
• Capturing the count number cost in timer on an event
• Between two activities finding the time c program languageperiod
• Time slicing for diverse responsibilities
• Time department multiplexing
• Scheduling of numerous obligations in RTOS

Question 11. Explain What Is A Watchdog Timer?

Answer :

A watchdog timer is an digital tool or electronic card that execute specific operation after certain term if some thing is going incorrect with an electronic machine.

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Question 12. Explain What Is The Need For An Infinite Loop In Embedded Systems?

Answer :

Embedded systems require countless loops for time and again processing or tracking the state of the program.  For example, the case of a software country continuously being confirmed for any first-rate mistakes that could simply take place at some stage in run-time such as memory outage or divide by way of zero, and so forth.

Red Hat Linux Essentials Interview Questions
Question 13. List Out Some Of The Commonly Found Errors In Embedded Systems?

Answer :

Some of the generally located errors in embedded systems are
• Damage of reminiscence gadgets static discharges and brief cutting-edge
• Address line malfunctioning because of a short in circuit
• Data traces malfunctioning
• Due to garbage or mistakes some reminiscence locations being inaccessible in garage
• Inappropriate insertion of reminiscence devices into the reminiscence slots
• Wrong manipulate alerts

Question 14. Explain What Is Semaphore?

Answer :

A semaphore is an summary datatype or variable that is used for controlling get admission to, by way of multiple tactics to a not unusual aid in a concurrent device which include multiprogramming running system.  Semaphores are commonly used for 2 functions

• To proportion a common reminiscence area
• To share get admission to to files

Question 15. When One Must Use Recursion Function? Mention What Happens When Recursion Functions Are Declared Inline?

Answer :

Recursion characteristic can be used whilst you are aware about the variety of recursive calls isn't immoderate. Inline capabilities assets says each time it's going to referred to as, it's going to reproduction the entire definition of that feature. Recursive characteristic declared as inline creates the load at the compilers execution.

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Question 16. Explain Whether We Can Use Semaphore Or Mutex Or Spinlock In Interrupt Context In Linux Kernel?

Answer :

Semaphore or Mutex can not be used for interrupt context in Linux Kernel. While spinlocks may be used for locking in interrupt context.

Question 17. What Is The Need For An Infinite Loop In Embedded Systems?

Answer :

Infinite Loops are the ones program constructs where in there's no break statement so that it will get out of the loop, it simply keeps looping over the statements within the block defined.

Example:

While(Boolean True) OR for(;;);

//Code


Embedded systems want limitless loops for time and again processing/tracking the country of the program. One example might be the case of a program country continuously being checked for any brilliant mistakes that might simply arise at some stage in run time consisting of memory outage or divide by way of zero etc.,

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Question 18. A Vast Majority Of High Performance Embedded Systems Today Use Risc Architecture Why?

Answer :

•According to the training sets used, computer systems are typically categorized into RISC and CISC. RISC stands for 'Reduced Instruction Set Computing' . The layout philosophy of RISC structure is such that simplest one training is done on each machine cycle hence taking very much less time and dashing up whilst compared to their CISC counterparts.
•Here the use of registers is optimised as maximum of the memory get admission to operations are restrained to shop and cargo operations.
•Fewer and simple addressing modes, and easy education codecs results in extra efficiency, optimisation of compilers, re-company of code for higher throughput in phrases of area and time complexities. All these capabilities make it the choice of architecture in majority of the Embedded systems.
•CISC once more have their personal benefits and they may be preferred whenever the overall performance and compiler simplification are the troubles to be looked after.

Red Hat Linux System Administration Interview Questions
Question 19. Why Do We Need Virtual Device Drivers When We Have Physical Device Drivers?

Answer :

Device drivers are basically a hard and fast of modules/workouts with a purpose to take care of a tool for which an immediate manner of communique is not viable via the person's application software and these can be idea of as an interface for this reason preserving the machine small offering for minimalistic of additives of code, if any.

Physical tool drivers can’t carry out all of the logical operations needed in a machine in instances like IPC, Signals and so forth...

The primary reason for having digital tool drivers is to mimic the behaviour of certain hardware devices without it virtually being gift and those could be attributed to the high cost of the gadgets or the unavailability of such gadgets.

These essentially create an illusion for the users as though they may be the use of the real hardware and permit them to carryout their simulation results.

Examples may be using virtual drivers in case of Network simulators,additionally the help of virtual tool drivers in case a person runs an additional OS in a virtual box sort of a software.

Question 20. What Is The Need For Dmac In Es?

Answer :

•Direct memory access is especially used to overcome the risks of interrupt and progam managed I/O.
•DMA modules usually take the control over from the processor and carry out the memory operations and this is in particular due to the fact to counteract the mismatch in the processing speeds of I/O gadgets and the procesor. This is relatively quicker.
•It is an crucial part of any embedded structures,and the cause for their use is they may be used for bursty data transfers instead of single byte methods.
•It has to anticipate the structures resources inclusive of the machine bus in case it is already in control of it.

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Question 21. What Is Endianness Of A System And How Do Different Systems Communicate With Each Other?

Answer :

•Endianness basically refers to the ordering of the bytes inside words or larger bytes of statistics treated as a unmarried entity.
•When we recollect a several bytes of records say as an instance four bytes of statistics,XYZQ the lower byte if stored in a Higher deal with and others in successively decreasing addresses, then it refers back to the Big Endian and the vice versa of this refers to Little Endian structure.
•Intel 80x86 normally follows Little Endian and others like IBM systems comply with Big Endian formats.
•If the facts is being transmitted care has to be taken with a purpose to realize as to which byte,whether the better or the decrease byte is being transmitted.
•Hence a common layout prior to communication has to be agreed upon to avoid incorrect interpretation/calculations.
•Usually layer modules are written with a view to automate those conversion in Operating structures.

Question 22. How Are Macros Different From Inline Functions?

Answer :

•Macros are usually used each time a set of commands/obligations must be repeatedly done. They are small packages to carryout some predefined movements.
•We usually use the #outline directive in case we want to define the values of a few constants so in case a trade is needed simplest the fee can be modified and is contemplated all through.
#define mul(a,b) (a*b) 
•The most important disadvantage of macros is that they may be now not sincerely features and the usual error checking and stepping thru of the code does now not occur. 
•Inline capabilities are extended on every occasion it's miles invoked instead of the manipulate going to the location where the function is described and avoids all of the sports such as saving the return deal with when a bounce is accomplished. Saves time in case of brief codes.
Inline waft upload(waft a,flow b)

 return a+b;

•Inline is just a request to the compiler and it's far upto to the compiler whether to replacement the code at the area of invocation or perform a bounce based totally on its performance algorithms.

Question 23. What Could Be The Reasons For A System To Have Gone Blank And How Would You Debug It?

Answer :

Possible reasons may be:
•PC being overheated.
•Dust having being amassed all round.
•CPU enthusiasts now not working properly .
•Faulty energy connections.
•Faulty circuit board from where the power is being drawn.
•Support Drivers no longer having being mounted. 
•Debugging steps which may be taken are:
•Cleaning the device very well and keeping it in a dust-free surroundings. Environment that is cool enough and enables for smooth passage of air must be ideal enough.
•By locating the precise support drivers for the machine in attention and having them hooked up.

Unix/Linux Interview Questions
Question 24. Explain Interrupt Latency And How Can We Decrease It?

Answer :

1.Interrupt latency essentially refers back to the time span an interrupt is generated and it being serviced through the suitable ordinary described, generally the interrupt handler.
2.External indicators, some circumstance inside the software or by way of the prevalence of some occasion, these can be the reasons for era of an interrupt.
3.Interrupts also can be masked in order to ignore them despite the fact that an occasion happens for which a recurring must be finished.
4.Following steps may be accompanied to reduce the latency

•ISRs being simple and short.
•Interrupts being serviced right now
•Avoiding the ones commands that increase the latency length.
•Also by prioritizing interrupts over threads.
•Avoiding use of irrelevant APIs.

Ubuntu Certified Professional Interview Questions
Question 25. How To Create A Child Process In Linux?

Answer :

Prototype of the characteristic used to create a baby technique is pid_t fork(void);
•Fork is the gadget name this is used to create a child manner. It takes no arguments and returns a cost of type pid_t.
•If the function succeeds it returns the pid of the child procedure created to its discern and toddler gets a 0 cost indicating its a success introduction.
•On failure, a -1 may be lower back inside the parent's context, no toddler system could be created, and errno might be set.
•The infant technique usually plays all its operations in its mother and father context but each procedure independently of 1 nother and additionally inherits a number of the crucial attributes from it together with UID, modern-day listing, root directory and so forth.

Significance of watchdog timer in Embedded Systems.
•Watchdog timer is basically a timing device that is set for predefined time c program languageperiod and some occasion have to occur throughout that point c program languageperiod else the device generates a day trip sign.
•One utility where it's far maximum widely used is while the cellular telephone hangs and no hobby takes location, in those instances watchdog timer performs a restart of the system and is derived to the rescue of the users.
•It is used to reset to the original country every time a few beside the point activities take vicinity which include too many commands being given at the same time or other sports that bring about malfunctioning of the GUI. It is usually operated by counter devices.

Question 26. If You Buy Some Rtos, What Are The Features You Look For In?

Answer :

•Deterministic working machine having assured worst-case interrupt latency and context-transfer times.
•Documentation imparting for the minimum, average, and maximum variety of clock cycles required with the aid of each device name.
•Interrupt response instances need to be very minute.
•Context transfer time must be very low.
•Compatibility with numerous plugin devices.
•Overall it need to be very reliable.

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Question 27. Why Is Java Mostly Used In Embedded Systems?

Answer :

•Java become specifically designed and conceptualised for code which could paintings on distinctive structures without any hassles and additionally for being relaxed enough which will no longer harm or corrupt different modules of code.
•Features like exception dealing with, simple syntax and Automatic Garbage series all work in its favour as the language for use in ES's.
•Also that it is extensively used inside the shape of Java applets makes it very popular confining it to the bounds of JVM. It is Dynamic in nature.
•Its use is likewise being exploited in organisation structures in the shape of J2EE, J2SE, J2ME in case of cell applications.

IBM AIX Interview Questions
Question 28. What Are The Commonly Found Errors In Embedded Systems?

Answer :

•Damage of reminiscence gadgets due to brief current and static discharges.
•Malfunctioning of cope with strains due to a quick inside the circuit.
•Malfunctioning of Data strains.
•Some reminiscence places being inaccessible in storage due to rubbish or mistakes.
•Improper insertion of Memory gadgets into the memory slots.
•Faulty manipulate alerts.

Question 29. What Is The Need For Having Multibyte Data Input And Output Buffers In Case Of Device Ports?

Answer :

•It’s normally the case that a few gadgets transfer the output both in a bursty or a sequential way and additionally during enter access. If we take the example of keyboards, all of the statistics entered is stored in a buffer and given at a time or one man or woman at a time.
•In case of networking there can be numerous requests to access the equal aid and all these are queued in a buffer and serviced inside the order they are acquired. Hence to avoid the enter/output devices from getting overloaded with requests, we use multibyte buffers.

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Question 30. What Is The Difference Between Hardware Design And Software Design?

Answer :

•Hardware design is designed with the collaboration of interconnected parallel additives that inherits the residences of each different. Whereas, Software layout is designed with sequential components, that are primarily based on items and threads.
•Hardware design shape doesn’t trade dynamically and it is able to’t be created, modified or removed without difficulty. Whereas, Software layout structure can be modified dynamically and re-usability functions, used to define the components. It additionally includes smooth introduction, modification and elimination of the components from the software program.
•Hardware layout specializes in character components which are represented the use of analytical version that makes use of the switch capabilities. Whereas, Software design constitute the additives the usage of computation version that can have abstract execution engine or it is able to use the digital machine which might be non-deterministic.




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