Hello Fiiends,Today I am posting some C Interview Questions and Answers . All the questions and their answers are taken from the site TechPreparation.com. You can go through this site for more interview questions. I hope this will help all of you.
Q. What is C language?
The C programming language is a standardized programming language developed in the early 1970s by Ken Thompson and Dennis Ritchie for use on the UNIX operating system. It has since spread to many other operating systems, and is one of the most widely used programming languages. C is prized for its efficiency, and is the most popular programming language for writing system software, though it is also used for writing applications.
Q. What is the output of printf("%d")?
- When we write printf("%d",x); this means compiler will print the value of x. But as here, there is nothing after %d so compiler will show in output window garbage value.
- When we use %d the compiler internally uses it to access the argument in the stack (argument stack). Ideally compiler determines the offset of the data variable depending on the format specification string. Now when we write printf("%d",a) then compiler first accesses the top most element in the argument stack of the printf which is %d and depending on the format string it calculated to offset to the actual data variable in the memory which is to be printed. Now when only %d will be present in the printf then compiler will calculate the correct offset (which will be the offset to access the integer variable) but as the actual data object is to be printed is not present at that memory location so it will print what ever will be the contents of that memory location.
Q. What is the difference between "printf(...)" and "sprintf(...)"?
sprintf(...) writes data to the character array whereas printf(...) writes data to the standard output device.
Q. Compilation How to reduce a final size of executable?
Size of the final executable can be reduced using dynamic linking for libraries.
Q. Can you tell me how to check whether a linked list is circular?
Create two pointers, and set both to the start of the list. Update each as follows:
while (pointer1)
{
pointer1 = pointer1->next;
pointer2 = pointer2->next;
if (pointer2) pointer2=pointer2->next;
if (pointer1 == pointer2)
{
print ("circular");
}
}
If a list is circular, at some point pointer2 will wrap around and be either at the item just before pointer1, or the item before that. Either way, its either 1 or 2 jumps until they meet.
Q. What are the different storage classes in C?
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 static specifier also have static scope.
- Memory obtained from calls to malloc(), alloc() or realloc() belongs to allocated storage class.
Q. How can you determine the size of an allocated portion of memory?
You can’t, really. free() can , but there’s no way for your program to know the trick free() uses. Even if you disassemble the library and discover the trick, there’s no guarantee the trick won’t change with the next release of the compiler.
Q. Can static variables be declared in a header file?
You can’t declare a static variable without defining it as well (this is because the storage class modifiers static and extern are mutually exclusive). A static variable can be defined in a header file, but this would cause each source file that included the header file to have its own private copy of the variable, which is probably not what was intended.
Q. Can a variable be both const and volatile?
Yes. The const modifier means that this code cannot change the value of the variable, but that does not mean that the value cannot be changed by means outside this code. For instance, in the example in FAQ 8, the timer structure was accessed through a volatile const pointer. The function itself did not change the value of the timer, so it was declared const. However, the value was changed by hardware on the computer, so it was declared volatile. If a variable is both const and volatile, the two modifiers can appear in either order.
Q. Can include files be nested?
Yes. Include files can be nested any number of times. As long as you use precautionary measures , you can avoid including the same file twice. In the past, nesting header files was seen as bad programming practice, because it complicates the dependency tracking function of the MAKE program and thus slows down compilation. Many of today’s popular compilers make up for this difficulty by implementing a concept called precompiled headers, in which all headers and associated dependencies are stored in a precompiled state.
Many programmers like to create a custom header file that has #include statements for every header needed for each module. This is perfectly acceptable and can help avoid potential problems relating to #include files, such as accidentally omitting an #include file in a module.
Q. What is a null pointer?
There are times when it’s necessary to have a pointer that doesn’t point to anything. The macro NULL, defined in , has a value that’s guaranteed to be different from any valid pointer. NULL is a literal zero,
possibly cast to void* or char*. Some people, notably C++ programmers, prefer to use 0 rather than NULL. The null pointer is used in three ways:
- To stop indirection in a recursive data structure
- As an error value
- As a sentinel value
Q. What is the difference between text and binary modes?
Streams can be classified into two types: text streams and binary streams. Text streams are interpreted, with a maximum length of 255 characters. With text streams, carriage return/line feed combinations are translated to the newline n character and vice versa. Binary streams are uninterrupted and are treated one byte at a time with no translation of characters. Typically, a text stream would be used for reading and writing standard text files, printing output to the screen or printer, or receiving input from the keyboard.
A binary text stream would typically be used for reading and writing binary files such as graphics or word processing documents, reading mouse input, or reading and writing to the modem.
Q. What is static memory allocation and dynamic memory allocation?
Static memory allocation: The compiler allocates the required memory space for a declared variable.By using the address of operator,the reserved address is obtained and this address may be assigned to a
pointer variable.Since most of the declared variable have static memory,this way of assigning pointer value to a pointer variable is known as static memory allocation. memory is assigned during compilation time.
Dynamic memory allocation: It uses functions such as malloc( ) or calloc( ) to get memory dynamically.If these functions are used to get memory dynamically and the values returned by these functions are assigned to pointer variables, such assignments are known as dynamic memory allocation.memory is assigned during run time.
Q. How are pointer variables initialized?
Pointer variable are initialized by one of the following two ways
- Static memory allocation
- Dynamic memory allocation
Q. 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.
Q. What is a method?
Method is a way of doing something, especially a systematic way; implies an orderly logical arrangement (usually in steps).
Q. 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.
Q. What is the difference between declaring a variable and defining a variable?
Declaring a variable means describing its type to the compiler but not allocating any space for it. Defining a variable means declaring it and also allocating space to hold the variable. You can also initialize a
variable at the time it is defined.
Refrence: http://techpreparation.com/
No comments:
Post a Comment