Monday, December 3, 2007

C Interview Questions And Answers -3

Question:WHat will be the result of the following code?

#define TRUE 0 // some code while(TRUE) { // some code }
This will not go into the loop as TRUE is defined as 0.

Question: What will be printed as the result of the operation below:

int x;
int modifyvalue(){
return(x+=10);
}
int changevalue(int x)
{
return(x+=1);
}
void main()
{
int x=10;
x++;
changevalue(x);
x++;
modifyvalue();
printf("First output:%d\n",x);
x++;
changevalue(x);
printf("Second output:%d\n",x);
modifyvalue();
printf("Third output:%d\n",x);
}
Answer: 12 , 13 , 13

Question: What will be printed as the result of the operation below:

main()
{
int x=10, y=15;
x = x++;
y = ++y;
printf(“%d %d\n”,x,y);
}
Answer: 11, 16

Question: What will be printed as the result of the operation below:

main()
{
int a=0;
if(a==0)
printf(“Tech Preparation\n”);
printf(“Tech Preparation\n”);
}
Answer: Two lines with “Tech Preparation” will be printed.

Question: What will the following piece of code do

int f(unsigned int x)
{
int i;
for (i=0; x!0; x>>=1)
{
if (x & 0X1)
i++;
}return i;
}
Answer: returns the number of ones in the input parameter X

Question: What will happen in these three cases?

if(a=0)
{
//somecode
}
if (a==0)
{
//do something
}
if (a===0)
{
//do something
}

Question: What are x, y, y, u
#define Atype int*
typedef int *p;
p x, z;
Atype y, u;

Answer: x and z are pointers to int. y is a pointer to int but u is just an integer variable

Question:What does static variable mean?

there are 3 main uses for the static.
1. If you declare within a function:It retains the value between function calls
2.If it is declared for a function name:By default function is extern..so it will be visible from other files if the function declaration is as static..it is invisible for the outer files
3. Static for global variables:By default we can use the global variables from outside files If it is static global..that variable is limited to with in the file

Question: Advantages of a macro over a function? Macro gets to see the Compilation environment, so it can expand __ __TIME__ __FILE__ #defines. It is expanded by the preprocessor.
For example, you can’t do this without macros
#define PRINT(EXPR) printf( #EXPR “=%d\n”, EXPR)
PRINT( 5+6*7 ) // expands into printf(”5+6*7=%d”, 5+6*7 );
You can define your mini language with macros:
#define strequal(A,B) (!strcmp(A,B))
Macros are a necessary evils of life. The purists don’t like them, but without it no real work gets done.

Question: What are the differences between malloc() and calloc()?

There are 2 differences. First, is in the number of arguments. malloc() takes a single argument(memory required in bytes), while calloc() needs 2 arguments(number of variables to allocate memory, size in bytes of a single variable). Secondly, malloc() does not initialize the memory allocated, while calloc() initializes the allocated memory to ZERO.


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