Device engineer Interview Questions

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Qualcomm
Embedded Software Engineer Device Drivers, Embedded Software Security Engineer was asked...December 1, 2011

what is volatile, static ? how would it affect if the static keyword used for big array inside a function? what are sections of memory and what kind of variable is stored where?

3 Answers

Just clarify one thing, the static variables within a function are not allocated to the function or thread's stack, instead, they are allocated to BSS area, just like other global variables. so it won't affect their function too much. Less

static variable is not stored on stack.

if Volatile used then the compiler dont consider to optimize that variable . Assume that a variable changed at the time of running . But some compiler optimized .to avoid that we use volatile. Static is the keyword which is used to initialized to once that means extra burden for a compiler to keep the variable .and permanantly allocate space in stack.if you diclare static array then stack overflow will occur. Less

Apple

If you have a diving board that is three body lengths long, 1 inch thick and shoulder width wide what dimension should you reduce if you want to decrease deflection the most for the least change?

3 Answers

Length

the thickness is the smallest value of L * w * h doubling the h, will yield 8x less deflection Less

Change the cross section from rectangle to a "T" or a "W"

Netflix

Write a contains function in javascript

3 Answers

HTMLElement.prototype.contains = HTMLElement.prototype.contains || function(child) { var children; var i; var node; if (this == child) { return true; } if (this.hasChildNodes) { for (i = 0, children = this.childNodes; i < children.length; i++) { node = children[i]; // skip for text nodes if (node.nodeType === 1 && (node == child || node.contains(child))) { return true; } } } return false; }; Less

function contains(needle, haystack) { var a = needle, b = haystack, result; return result = b.indexOf(a) !== -1 ? true : false; } Less

function checkContains() { var url = "this is the answer"; if(url.indexOf("answer")!=-1) alert("contains"); else alert("not contains"); } Less

Aptina Imaging

Which one is a more viable option for 45nm technology : NiSi2 vs CoSi2:

2 Answers

completely wrong answer... should be piping concern..

Below 50nm it is difficult to form CoSi2 on poly lines. NiSi2 had advantages such as less Si consumption with Ni than with Co. Also in case of NiSi2 cap layer is optional so that meant reduction in number of process steps. A single RTP step is sufficient for NiSi2. Less

SanDisk

What is gate induced barrier lowering effect?

2 Answers

It also can be confused with "Gate-Induced Drain Leakage", wich is different from DIBL. Due to the high e-field on Gate-Drain interface during off-state (with D-S bias), e-h pairs can be formed through tunneling. Each of them goes to the drain or channel and induces drain current. Please see : http://nanohub.org/resources/5690/download/2008.10.28-ece612-l16.pdf Less

I think it should be "Drain induced barrier lowering" which is related to the reduction in the threshold voltage of the transistor due to the large depletion region created by the Drain potential. " Less

Apple

Write a program to count the '1' bits of an integer.

1 Answers

int sumbits(uint32_t x) { int i,cnt; for (i=32,cnt=0;i>0;) { cnt+=(x>>(--i) & 0x1); } return cnt; } /* not sure if this is exact answer i wrote down there is other tricky solutions using x&(x-1) for those adept at bit hackery */ Less

Apple

Between the following materials, steel, magnesium, titanium, copper, aluminum, which is the most stiff and why? What does the stress strain plot look like for steel versus aluminum? What should you do if you want to increase the force until fracture? What would the stress strain plot look like if you took a material went until ultimate strength and then went back to zero stress and then went back to ultimate strength?

2 Answers

The answer is steel

Steel has the highest stiffness as defined by the Young’s modulus.

Apple

What are the multiple different ways of combining two rectangular bars of a metal into a T-shape

2 Answers

Welding, fastening etc.

Brass Brazing TIG/MIG welding Adhesives - LDA, PSA Fasteners Laser welding spot welding Magnets Over-molding a third component Less

GlobalFoundries

what's the most challenging problems in device engineering nowadays?

2 Answers

Device Mismatches, Sub-threshold/Gate/Junction Leakages, Reliability concerns, Stress effects ... to name a few. Less

to get performance on target without impacting yield and reliability

Amazon

White box Blackbox Sdlc Stlc Types of testing Levels of testing

2 Answers

it's a behavioural based testing i.e., testing internal structural logic design and implementation of different modules Less

it's internal structural design and implementation and it's UI and UX of the product tested which is not known to the tester Less

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