Technical Interview Questions
.Net Interview Questions
C++ Interview Questions
Unix Interview Questions
C Interview Questions e-book
Aptitude Interview Questions
C/C++ Aptitude Questions
C Aptitude Questions
C Interview Questions and Answers
What are the advantages of the functions?
- Debugging is easier
- It is easier to understand the logic involved in the program
- Testing is easier
- Recursive call is possible
- Irrelevant details in the user point of view are hidden in functions
- Functions are helpful in generalizing the program
Is NULL always defined as 0?
NULL is defined as either 0 or (void*)0. These values are almost
identical; either a literal zero or a void pointer is converted
automatically to any kind of pointer, as necessary, whenever a pointer
is needed (although the compiler canít always tell when a pointer is
What is the difference between NULL and NUL?
NULL is a macro defined in for the null pointer.
NUL is the name of the first character in the ASCII character set. It
corresponds to a zero value. Thereís no standard macro NUL in C, but
some people like to define it.
The digit 0 corresponds to a value of 80, decimal. Donít confuse the
digit 0 with the value of Ďí (NUL)! NULL can be defined as ((void*)0),
NUL as Ďí.
Can the sizeof operator be used to tell the size of an array passed
to a function?
No. Thereís no way to tell, at runtime, how many elements are in an
array parameter just by looking at the array parameter itself. Remember,
passing an array to a function is exactly the same as passing a pointer
to the first element.
Is using exit() the same as using return?
No. The exit() function is used to exit your program and return control
to the operating system. The return statement is used to return from a
function and return control to the calling function. If you issue a
return from the main() function, you are essentially returning control
to the calling function, which is the operating system. In this case,
the return statement and exit() function are similar.
Can math operations be performed on a void pointer?
No. Pointer addition and subtraction are based on advancing the pointer
by a number of elements. By definition, if you have a void pointer, you
donít know what itís pointing to, so you donít know the size of what
itís pointing to. If you want pointer arithmetic to work on raw
addresses, use character pointers.
Can the size of an array be declared at runtime?
No. In an array declaration, the size must be known at compile time. You
canít specify a size thatís known only at runtime. For example, if i is
a variable, you canít write code like this:
char array[i]; /* not valid C */
Some languages provide this latitude. C doesnít. If it did, the stack
would be more complicated, function calls would be more expensive, and
programs would run a lot slower. If you know that you have an array but
you wonít know until runtime how big it will be, declare a pointer to it
and use malloc() or calloc() to allocate the array from the heap.
Can you add pointers together? Why would you?
No, you canít add pointers together. If you live at 1332 Lakeview Drive,
and your neighbor lives at 1364 Lakeview, whatís 1332+1364? Itís a
number, but it doesnít mean anything. If you try to perform this type of
calculation with pointers in a C program, your compiler will complain.
The only time the addition of pointers might come up is if you try to
add a pointer and the difference of two pointers.
Are pointers integers?
No, pointers are not integers. A pointer is an address. It is merely a
positive number and not an integer.
How do you redirect a standard stream?
Most operating systems, including DOS, provide a means to redirect
program input and output to and from different devices. This means that
rather than your program output (stdout) going to the screen; it can be
redirected to a file or printer port. Similarly, your programís input (stdin)
can come from a file rather than the keyboard. In DOS, this task is
accomplished using the redirection characters, < and >. For example, if
you wanted a program named PRINTIT.EXE to receive its input (stdin) from
a file named STRINGS.TXT, you would enter the following command at the
C:> PRINTIT <STRINGS.TXT
Notice that the name of the executable file always comes first. The
less-than sign (<) tells DOS to take the strings contained in
STRINGS.TXT and use them as input for the PRINTIT program.
The following example would redirect the programís output to the prn
device, usually the printer attached on LPT1:
C :> REDIR > PRN
Alternatively, you might want to redirect the programís output to a
file, as the following example shows:
C :> REDIR > REDIR.OUT
In this example, all output that would have normally appeared on-screen
will be written to the file
Redirection of standard streams does not always have to occur at the
operating system. You can redirect a standard stream from within your
program by using the standard C library function named freopen(). For
example, if you wanted to redirect the stdout standard stream within
your program to a file named OUTPUT.TXT, you would implement the freopen()
function as shown here:
... freopen(output.txt, w, stdout);
Now, every output statement (printf(), puts(), putch(), and so on) in
your program will appear in the file OUTPUT.TXT.
What is a method?
Method is a way of doing something, especially a systematic way; implies
an orderly logical arrangement (usually in steps).
What is the easiest searching method to use?
Just as qsort() was the easiest sorting method, because it is part of
the standard library, bsearch() is the easiest searching method to use.
If the given array is in the sorted order bsearch() is the best method.
Following is the prototype for bsearch():
void *bsearch(const void *key, const void *buf, size_t num, size_t size,
int (*comp)(const void *, const void*));
Another simple searching method is a linear search. A linear search is
not as fast as bsearch() for searching among a large number of items,
but it is adequate for many purposes. A linear search might be the only
method available, if the data isnít sorted or canít be accessed
randomly. A linear search starts at the beginning and sequentially
compares the key to each element in the data set.
Is it better to use a pointer to navigate an array of values, or is it
better to use a subscripted array name?
Itís easier for a C compiler to generate good code for pointers than for
What is indirection?
If you declare a variable, its name is a direct reference to its value.
If you have a pointer to a variable, or any other object in memory, you
have an indirect reference to its value.
How are portions of a program disabled in demo versions?
If you are distributing a demo version of your program, the preprocessor
can be used to enable or disable portions of your program. The following
portion of code shows how this task is accomplished, using the
preprocessor directives #if and #endif:
int save_document(char* doc_name)
printf(Sorry! You canít save documents using the DEMO version of this
Page Numbers :