Technical Questions on Digital Electronics

if we are measuring dc voltage of battery then why would we get ac voltage component in it?
A signed no is stored in 10-bit register, what is the max and min possible value of the number. Cadence
Which range of signals are used for terrestrial transmission?
what happen when unit step signal is applied to a integrater circuit.explain with graph BARC
How can you convert an SR Flip-flop to a JK Flip-flop?
differnce between timer & counter TCS
HI FRDS AM saranya i did BE (2009 PASSOUT)I PLAN TO DO DOTNET. CAN ANYBODY TELL ME WHICH TRINEE CENTRE WILL BE BEST FOR DOTNET WITH PLACEMENTS
What are Rectifiers and what is the use of it?
i/p sec of atransformer is 230V 5a o/p spc is 12v 1a so i/p power will be 1150w o/p power will be 12w then how the power transfer theorm matching with this?? Bosch
why is there -48 v DC voltage use in CISCO Router.?? is there any advatage to use this type of negative voltage rather than positive voltage??
in a distortion factor meter , the filter at the front end is used supress ?
what is the physical need to find 3bd frequencies?
why scanning is necessary in t.v. transmission and why it is carried out at fast rate?
why we use vsb transmission for video signal transmission and why dont we use ssb transmission?
what is unijunction transistor(ujt)?
Which type of architecture 8085 has?
Telecom BSS related ques: For cascaded 1800 BTS with master 900 BTS,if 900 master BTS is down for its own equipment fault,cascaded slave 1800 BTS gets down/stop carrying traffic without any fault as BCCH and other controllong channels are in master 900 BTS.Is there any technology/system to turn the slave 1800 BTS to a single 1800 BTS autometcally when 900 master BTS is down for its own equipment fault???It is possible to make the slave 1800 BTS single live BTS manually.But I want to know the autometic system/process.if there is any....if not available, how can we generate the system?? Grameen-Phone
What is JKMS FF?
what is a MEMS sensor? What is its advantage? Bosch
Distinguish between Angle modulation and Amplitude modulation

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Technical Interview PHP tutorial

Here is some PHP Interview Questions, that will helpfull to PHP Interview Candidates

1. What is CAPTCHA?

CAPTCHA stands for Completely Automated Public Turing Test to tell Computers and Humans Apart. To prevent spammers from using bots to automatically fill out forms, CAPTCHA programmers will generate an image containing distorted images of a string of numbers and letters. Computers cannot determine what the numbers and letters are from the image but humans have great pattern recognition abilities and will be able to fairly accurately determine the string of numbers and letters. By entering the numbers and letters from the image in the validation field, the application can be fairly assured that there is a human client using it. To read more look here:
http://en.wikipedia.org/wiki/Captcha


2. What is difference between require_once(), require(), include().
Becouse above three function usely use to call a file in another file?

Difference between require() and require_once(): require() includes and evaluates a specific file, while require_once() does that only if it has not been included before (on the same page). So, require_once() is recommended to use when you want to include a file where you have a lot of functions for example. This way you make sure you don't include the file more times and you will not get the "function re-declared" error. Difference between require() and include() is that require() produces a FATAL ERROR if the file you want to include is not found, while include() only produces a WARNING. There is also include_once() which is the same as include(), but the difference between them is the same as the difference between require() and require_once().


3. If you have to work with dates in the following format: "Tuesday, February 14, 2006 @ 10:39 am", how can you convert them to another format, that is easier to use?

The strtotime function can convert a string to a timestamp. A timestamp can be converted to date format. So it is best to store the dates as timestamp in the database, and just output them in the format you like.

So let's say we have
$date = "Tuesday, February 14, 2006 @ 10:39 am";
In order to convert that to a timestamp, we need to get rid of the "@" sign, and we can use the remaining string as a parameter for the strtotime function.

So we have
$date = str_replace("@ ","",$date);
$date = strtotime($date);

now $date is a timestamp
and we can say:

echo date("d M Y",$date);


4. How we know browser properties?

get_browser() attempts to determine the capabilities of the user's browser. This is done by looking up the browser's information in the browscap.ini file.

echo $_SERVER['HTTP_USER_AGENT'] . "

---

\n";

$browser = get_browser();

foreach ($browser as $name => $value) {
echo "$name $value
\n";
}


5. How i will check that user is, logged in or not. i want to make it a function and i want to use in each page and after login i want to go in current page(same page. where i was working)?

For this we can use the session objec($_SESSION)t. When the user login with his/ her user name and password, usually we check those to ensure for correctness. If that user name and password are valid one then we can store that user name in a session and then we can very that session variable has been set or not in a single files and we can include that file in all pages.

6. How i can get ip address?

We can use SERVER var $_SERVER['SERVER_ADDR'] and getenv("REMOTE_ADDR") functions to get the IP address.

7. What is differenc between mysql_connect and mysql_pconnec?

mysql_pconnect establishes a persistent connection. If you don't need one (such as a website that is mostly HTML files or PHP files that don't call the db) then you don't need to use it. mysql_connect establishes a connection for the duration of the script that access the db. Once the script has finished executing it closes the connection. The only time you need to close the connection manually is if you jump out of the script for any reason.

If you do use mysql_pconnect. You only need to call it once for the session. That's the beauty of it. It will hold open a connection to the db that you can use over and over again simply by calling the resource ID whenever you need to interact with the db.

8. What is the difference between echo and print statement?

There is a slight difference between print and echo which would depend on how you want to use the outcome. Using the print method can return a true/false value. This may be helpful during a script execution of somesort. Echo does not return a value, but has been considered as a faster executed command. All this can get into a rather complicated discussion, so for now, you can just use whichever one you prefer.

9. How to make a download page in own site, which i can know that how many file has been loaded by particular user or particular ipaddress?

We can use hyperlink having URL where file are kept. and we only allow regisetered user to download. from session of user we can get the user detail

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Technical Interview "C" Q & A Part 2

Predict the output or error(s) for the following:

1. main()
{
int i, n;
char *x = “girl”;
n = strlen(x);
*x = x[n];
for(i=0; i
{
printf(“%s\n”,x);
x++;
}
}

Answer:
(blank space)
irl
rl
l

Explanation:
Here a string (a pointer to char) is initialized with a value “girl”. The strlen function returns
the length of the string, thus n has a value 4. The next statement assigns value at the nth location
(‘\0’) to the first location. Now the string becomes “\0irl” . Now the printf statement prints the
string after each iteration it increments it starting position. Loop starts from 0 to 4. The first
time x[0] = ‘\0’ hence it prints nothing and pointer value is incremented. The second time it prints
from x[1] i.e “irl” and the third time it prints “rl” and the last time it prints “l” and the loop
terminates.

2. int i,j;
for(i=0;i<=10;i++)
{
j+=5;
assert(i<5);
}

Answer:
Runtime error: Abnormal program termination.
assert failed (i<5), ,

Explanation:
asserts are used during debugging to make sure that certain conditions are satisfied. If assertion
fails, the program will terminate reporting the same. After debugging use,
#undef NDEBUG
and this will disable all the assertions from the source code. Assertion
is a good debugging tool to make use of.

3. main()
{
int i=-1;
+i;
printf("i = %d, +i = %d \n",i,+i);
}

Answer:
i = -1, +i = -1

Explanation:
Unary + is the only dummy operator in C. Where-ever it comes you can just ignore it just because it has
no effect in the expressions (hence the name dummy operator).

4. What are the files which are automatically opened when a C file is executed?
Answer:
stdin, stdout, stderr (standard input,standard output,standard error).

5. what will be the position of the file marker?
a: fseek(ptr,0,SEEK_SET);
b: fseek(ptr,0,SEEK_CUR);

Answer :
a: The SEEK_SET sets the file position marker to the starting of the file.
b: The SEEK_CUR sets the file position marker to the current position
of the file.

6. main()
{
char name[10],s[12];
scanf(" \"%[^\"]\"",s);
}
How scanf will execute?
Answer:
First it checks for the leading white space and discards it.Then it matches with a quotation mark and then
it reads all character upto another quotation mark.

7. What is the problem with the following code segment?
while ((fgets(receiving array,50,file_ptr)) != EOF)
;
Answer & Explanation:
fgets returns a pointer. So the correct end of file check is checking for != NULL.

8. main()
{
main();
}

Answer:
Runtime error : Stack overflow.

Explanation:
main function calls itself again and again. Each time the function is called its return address is stored in
the call stack. Since there is no condition to terminate the function call, the call stack overflows at runtime.
So it terminates the program and results in an error.

9. main()
{
char *cptr,c;
void *vptr,v;
c=10; v=0;
cptr=&c; vptr=&v;
printf("%c%v",c,v);
}

Answer:
Compiler error (at line number 4): size of v is Unknown.

Explanation:
You can create a variable of type void * but not of type void, since void is an empty type. In the second
line you are creating variable vptr of type void * and v of type void hence an error.

10. main()
{
char *str1="abcd";
char str2[]="abcd";
printf("%d %d %d",sizeof(str1),sizeof(str2),sizeof("abcd"));
}

Answer:
2 5 5

Explanation:
In first sizeof, str1 is a character pointer so it gives you the size of the pointer variable. In second sizeof
the name str2 indicates the name of the array whose size is 5 (including the '\0' termination character).
The third sizeof is similar to the second one.

11. main()
{
char not;
not=!2;
printf("%d",not);
}

Answer:
0

Explanation:
! is a logical operator. In C the value 0 is considered to be the boolean value FALSE, and any non-zero value
is considered to be the boolean value TRUE. Here 2 is a non-zero value so TRUE. !TRUE is FALSE (0) so it prints 0.

12. #define FALSE -1
#define TRUE 1
#define NULL 0
main() {
if(NULL)
puts("NULL");
else if(FALSE)
puts("TRUE");
else
puts("FALSE");
}

Answer:
TRUE

Explanation:
The input program to the compiler after processing by the preprocessor is,
main(){
if(0)
puts("NULL");
else if(-1)
puts("TRUE");
else
puts("FALSE");
}
Preprocessor doesn't replace the values given inside the double quotes. The check by if condition is boolean
value false so it goes to else. In second if -1 is boolean value true hence "TRUE" is printed.

13. main()
{
int k=1;
printf("%d==1 is ""%s",k,k==1?"TRUE":"FALSE");
}

Answer:
1==1 is TRUE

Explanation:
When two strings are placed together (or separated by white-space) they are concatenated (this is called as
"stringization" operation). So the string is as if it is given as "%d==1 is %s". The conditional operator( ?: )
evaluates to "TRUE".

14. main()
{
int y;
scanf("%d",&y); // input given is 2000
if( (y%4==0 && y%100 != 0) || y%100 == 0 )
printf("%d is a leap year");
else
printf("%d is not a leap year");
}

Answer:
2000 is a leap year

Explanation:
An ordinary program to check if leap year or not.

15. #define max 5
#define int arr1[max]
main()
{
typedef char arr2[max];
arr1 list={0,1,2,3,4};
arr2 name="name";
printf("%d %s",list[0],name);
}

Answer:
Compiler error (in the line arr1 list = {0,1,2,3,4})

Explanation:
arr2 is declared of type array of size 5 of characters. So it can be used to declare the variable name of
the type arr2. But it is not the case of arr1. Hence an error.
Rule of Thumb:
#defines are used for textual replacement whereas typedefs are used for declaring new types.

16. int i=10;
main()
{
extern int i;
{
int i=20;
{
const volatile unsigned i=30;
printf("%d",i);
}
printf("%d",i);
}
printf("%d",i);
}

Answer:
30,20,10

Explanation:
'{' introduces new block and thus new scope. In the innermost block i is declared as,
const volatile unsigned
which is a valid declaration. i is assumed of type int. So printf prints 30. In the next block, i has value 20
and so printf prints 20. In the outermost block, i is declared as extern, so no storage space is allocated for it.
After compilation is over the linker resolves it to global variable i (since it is the only variable visible there).
So it prints i's value as 10.

17. main()
{
int *j;
{
int i=10;
j=&i;
}
printf("%d",*j);
}

Answer:
10

Explanation:
The variable i is a block level variable and the visibility is inside that block only. But the lifetime of i is
lifetime of the function so it lives upto the exit of main function. Since the i is still allocated space,
*j prints the value stored in i since j points i.

18. main()
{
int i=-1;
-i;
printf("i = %d, -i = %d \n",i,-i);
}

Answer:
i = -1, -i = 1

Explanation:
-i is executed and this execution doesn't affect the value of i. In printf first you just print the value of i.
After that the value of the expression -i = -(-1) is printed.

19. #include
main()
{
const int i=4;
float j;
j = ++i;
printf("%d %f", i,++j);
}

Answer:
Compiler error

Explanation:
i is a constant. you cannot change the value of constant

20. #include
main()
{
int a[2][2][2] = { {10,2,3,4}, {5,6,7,8} };
int *p,*q;
p=&a[2][2][2];
*q=***a;
printf("%d..%d",*p,*q);
}

Answer:
garbagevalue..1

Explanation:
p=&a[2][2][2] you declare only two 2D arrays. but you are trying to access the third 2D
(which you are not declared)
it will print garbage values. *q=***a starting address of a is assigned integer pointer.
now q is pointing to starting address of a.if you print *q meAnswer:it will print first
element of 3D array.

21. #include
main()
{
register i=5;
char j[]= "hello";
printf("%s %d",j,i);
}

Answer:
hello 5

Explanation:
if you declare i as register compiler will treat it as ordinary integer and it will take
integer value. i value may be stored either in register or in memory.

22. main()
{
int i=5,j=6,z;
printf("%d",i+++j);
}

Answer:
11

Explanation:
the expression i+++j is treated as (i++ + j)

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