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Q:The following variable is available in file1.c,
who can access it?: static int average;
Ans: all the functions in the file1.c can access the variable.
Q:WHat will be the result of the following code?
#define TRUE 0 // some code while(TRUE) { // some code }
Ans:This will not go into the loop as TRUE is defined as 0.
Q: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);
}
Ans:12 , 13 , 13
Q: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);
}
Ans: 11, 16
Q: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”);
}
Ans:Two lines with “Tech Preparation” will be printed.
Q: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;
}
Ans: returns the number of ones in the input parameter X
Q:What will happen in these three cases?
if(a=0){
//somecode
}
if (a==0){
//do something
}
if (a===0){
//do something
}
What are x, y, y, u
#define Atype int*
typedef int *p;
p x, z;
Atype y, u;
Ans: x and z are pointers to int. y is a pointer to int but u is just
an integer variable
Q:What does static variable mean?
Ans: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
Q:Advantages of a macro over a function?
Ans: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.
Q:What are the differences between malloc() and calloc()?
Ans: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.
Q:What are the different storage classes in C?
Ans:C has three types of storage: automatic, static and allocated.
Variable having block scope and without static specifier have automatic
storage duration.
Variables with block scope, and with static specifier have static scope.
Global variables (i.e, file scope) with or without the the static specifier
also have static scope.
Memory obtained from calls to malloc(), alloc() or realloc() belongs to
allocated storage class.
Q:What is the difference between strings and
character arrays?
Ans:A major difference is: string will have static storage duration,
whereas as a character array will not, unless it is explicity specified by
using the static keyword.
Actually, a string is a character array with following properties:
* the multibyte character sequence, to which we generally call string, is used
to initialize an array of static storage duration. The size of this array is
just sufficient to contain these characters plus the terminating NUL
character.
* it not specified what happens if this array, i.e., string, is modified.
* Two strings of same value[1] may share same memory area. For example, in the
following declarations:
char *s1 = “Calvin and Hobbes”;
char *s2 = “Calvin and Hobbes”;
the strings pointed by s1 and s2 may reside in the same memory location. But,
it is not true for the following:
char ca1[] = “Calvin and Hobbes”;
char ca2[] = “Calvin and Hobbes”;
[1] The value of a string is the sequence of the values of the contained
characters, in order.
Q:Write down the equivalent pointer expression for referring the same
element a[i][j][k][l]?
Ans:
a[i] == *(a+i)
a[i][j] == *(*(a+i)+j)
a[i][j][k] == *(*(*(a+i)+j)+k)
a[i][j][k][l] == *(*(*(*(a+i)+j)+k)+l)