Professional Device Drivers Interview Questions & Answers:

1. The major number identifies the _____ associated with the device.
a) driver
b) protocol
c) port
d) none of the mentioned

a) driver

2. The kernel identifies the driver with its:
a) module
b) major number
c) device file
d) none of the mentioned

b) major number

3. In linux kernel 2.4, we can have:
a) 256 character drivers only
b) 256 block drivers only
c) 256 character drivers and 256 block drivers at the same time
d) none of the mentioned

c) 256 character drivers and 256 block drivers at the same time

4. The connection between the device file and device driver is based on the:
a) name of device file
b) number of device file
c) both (a) and (b)
d) none of the mentioned

b) number of device file

5. Do you know what is the output of this program?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
char *ptr;
memcpy(ptr,"google",11);
printf("%sn",ptr);
return 0;
}
a) google
b) segmentation fault
c) syntax error
d) none of the mentioned

b) segmentation fault
Explanation:
Memory must be allocated to pointer "ptr".
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
Segmentation fault (core dumped)
[root@localhost google]#

6. This program will allocate the memory of ___ bytes for pointer "ptr".

#include<stdio.h>
#include<stdlib.h>

int main()
{
int *ptr;
ptr = realloc(0,sizeof(int)*10);
return 0;
}
a) 0
b) 10
c) 40
d) none of the mentioned

c) 40
Explanation:
If the first argument of realloc() is NULL, then it behaves just like malloc().

7. What is the output of this program?

#include<stdio.h>
#include<stdlib.h>

int main()
{
char *ptr;
free(ptr);
return 0
}
a) this program will print nothing after execution
b) segmentation fault
c) Aborted (core dumped)
d) none of the mentioned

c) Aborted (core dumped)

8. Tell me what is the output of this program?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
char *ptr;
memcpy(ptr,"google",11);
printf("%sn",ptr);
return 0;
}
a) google
b) segmentation fault
c) syntax error
d) none of the mentioned

9. What is the output of this program?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
char *ptr;
ptr = (char*)malloc(sizeof(char)*11);
strcpy(ptr,"google");
printf("%dn",*ptr);
return 0;
}
a) s
b) google
c) 115
d) segmentation fault

c) 115
Explanation:
This program will print the equivalent decimal value at location pointed by "ptr".
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
115
[root@localhost google]#

10. Which one of the following in true about this program?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
char *ptr;
printf("%pn",ptr);
ptr = (char *)malloc(sizeof(char));
printf("%pn",ptr);
return 0;
}
a) this program will give segmentation fault
b) this program will print two same values
c) this program has some syntax error
d) none of the mentioned

d) none of the mentioned
Explanation:
This program will print two different values.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
0x4a77cff4
0x980c008
[root@localhost google]#

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11. In this program the two printed memory locations has the difference of ___ bytes.

#include<stdio.h>
#include<stdlib.h>

int main()
{
int *ptr;
ptr = (int*)malloc(sizeof(int)*2);
printf("%pn",ptr);
printf("%pn",ptr+1);
return 0;
}
a) 1
b) 4
c) can not be determined
d) none of the mentioned

b) 4
Explanation:
Pointer will increment by 4 bytes because it is the types of integer.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
0x9b4e008
0x9b4e00c
[root@localhost google]#

12. What is the output of this program?

#include<stdio.h>
#inlcude<stdlib.h>

int main()
{
int *ptr;
double *ptr;
printf("%dn",sizeof(ptr));
return 0;
}
a) 4
b) 8
c) the compiler will give the error
d) segmentaion fault

c) the compiler will give the error
Explanation:
Just see the output carefully.
Output:
[root@localhost google]# gcc -o san san.c
san.c: In function 'main':
san.c:8:10: error: conflicting types for 'ptr'
san.c:7:7: note: previous declaration of 'ptr' was here
[root@localhost google]#

13. What is the output of this program?

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
int ptr;
ptr = (int)malloc(sizeof(int)*10);
return 0;
}
a) syntax error
b) segmentaion fault
c) run time error
d) none of the mentioned

d) none of the mentioned
Explanation:
The memory has been allocated but we can not access rest of the memory other than 4 bytes.
Output:
[root@localhost google]# gcc -o san san.c
[root@localhost google]# ./san
[root@localhost google]#

14. Which one of the following is not true?
a) dynamic allocation of major numbers is not possible
b) major number can not be shared among drivers
c) both (a) and (b)
d) none of the mentioned

c) both (a) and (b)

15. The minor number range should be:
a) 0 to 15
b) 0 to 63
c) 0 to 255
d) none of the mentioned

c) 0 to 255

16. In we use a driver for N number of files, then we have to create ____ device files.
a) N
b) 1
c) N-1
d) none of the mentioned

a) N

17. In linux, a device driver can work without the:
a) major number
b) minor number
c) device file name
d) none of the mentioned

d) none of the mentioned

18. In linux kernel 2.1, the minor numbers were used to:
a) represent the sub-functionalitites of the driver
b) identify the driver
c) represent the device files
d) none of the mentioned

a) represnt the sub-functionalitites of the driver

19. If we use a driver for various device files, then:
a) minor number will be different for every device file
b) minor number will be same for every device file
c) minor number can not be allocated for any device file
d) none of the mentioned

a) minor number will be different for every device file