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Sample Technical Questions

C Sample Question

60. 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.

61. 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.

62. 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.

63. #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.

64. 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".

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