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Computer Interview Questions Answers

C Interview Questions Answers

Question - 21 : - What is a pointer variable?

Answer - 21 : - A pointer variable is a variable that may contain the address of another variable or any valid address in the memory.

Question - 22 : - Can static variables be declared in a header file?

Answer - 22 : - 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.

Question - 23 : - What is the quickest searching method to use?

Answer - 23 : - A binary search, such as bsearch() performs, is much faster than a linear search. A hashing algorithm can provide even faster searching. One particularly interesting and fast method for searching is to keep the data in a digital trie. A digital trie offers the prospect of being able to search for an item in essentially a constant amount of time, independent of how many items are in the data set. A digital trie combines aspects of binary searching, radix searching, and hashing. The term digital trie refers to the data structure used to hold the items to be searched. It is a multilevel data structure that branches N ways at each level.

Question - 24 : - What is Polymorphism ?

Answer - 24 : - 'Polymorphism' is an object oriented term. Polymorphism may be defined as the ability of related objects to respond to the same message with different, but appropriate actions. In other words, polymorphism means taking more than one form. Polymorphism leads to two important aspects in Object Oriented terminology - Function Overloading and Function Overriding. Overloading is the practice of supplying more than one definition for a given function name in the same scope. The compiler is left to pick the appropriate version of the function or operator based on the arguments with which it is called. Overriding refers to the modifications made in the sub class to the inherited methods from the base class to change their behavior.

Question - 25 : - What is a void pointer?

Answer - 25 : - A void pointer is a C convention for a raw address. The compiler has no idea what type of object a void Pointer really points to. If you write int *ip; ip points to an int. If you write void *p; p doesn’t point to a void! In C and C++, any time you need a void pointer, you can use another pointer type. For example, if you have a char*, you can pass it to a function that expects a void*. You don’t even need to cast it. In C (but not in C++), you can use a void* any time you need any kind of pointer, without casting. (In C++, you need to cast it). A void pointer is used for working with raw memory or for passing a pointer to an unspecified type. Some C code operates on raw memory. When C was first invented, character pointers (char *) were used for that. Then people started getting confused about when a character pointer was a string, when it was a character array, and when it was raw memory.

Question - 26 : - Can include files be nested?

Answer - 26 : - Answer 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.

Question - 27 : - How are pointer variables initialized?

Answer - 27 : - Pointer variable are initialized by one of the following two ways - Static memory allocation - Dynamic memory allocation

Question - 28 : - What is the quickest sorting method to use?

Answer - 28 : - The answer depends on what you mean by quickest. For most sorting problems, it just doesn’t matter how quick the sort is because it is done infrequently or other operations take significantly more time anyway. Even in cases in which sorting speed is of the essence, there is no one answer. It depends on not only the size and nature of the data, but also the likely order. No algorithm is best in all cases. There are three sorting methods in this author’s toolbox that are all very fast and that are useful in different situations. Those methods are quick sort, merge sort, and radix sort. The Quick Sort The quick sort algorithm is of the divide and conquer type. That means it works by reducing a sorting problem into several easier sorting problems and solving each of them. A dividing value is chosen from the input data, and the data is partitioned into three sets: elements that belong before the dividing value, the value itself, and elements that come after the dividing value. The partitioning is performed by exchanging elements that are in the first set but belong in the third with elements that are in the third set but belong in the first Elements that are equal to the dividing element can be put in any of the three setsthe algorithm will still work properly. The Merge Sort The merge sort is a divide and conquer sort as well. It works by considering the data to be sorted as a sequence of already-sorted lists (in the worst case, each list is one element long). Adjacent sorted lists are merged into larger sorted lists until there is a single sorted list containing all the elements. The merge sort is good at sorting lists and other data structures that are not in arrays, and it can be used to sort things that don’t fit into memory. It also can be implemented as a stable sort. The Radix Sort The radix sort takes a list of integers and puts each element on a smaller list, depending on the value of its least significant byte. Then the small lists are concatenated, and the process is repeated for each more significant byte until the list is sorted. The radix sort is simpler to implement on fixed-length data such as ints.

Question - 29 : - How can method defined in multiple base classes with same name can be invoked from derived class simultaneously

Answer - 29 : - class x { public: m1(); }; class y { public: m1(); }; class z :public x, public y { public: m1() { x::m1(); y::m1(); } };

Question - 30 : - What is a macro, and how do you use it?

Answer - 30 : - A macro is a preprocessor directive that provides a mechanism for token replacement in your source code. Macros are created by using the #define statement. Here is an example of a macro: Macros can also utilize special operators such as the stringizing operator (#) and the concatenation operator (##).The stringizing operator can be used to convert macro parameters to quoted strings, as in the following example: #define DEBUG_VALUE(v) printf(#v is equal to %d.n, v) In your program, you can check the value of a variable by invoking the DEBUG_VALUE macro: ... int x = 20; DEBUG_VALUE(x); ... The preceding code prints x is equal to 20. on-screen. This example shows that the stringizing operator used with macros can be a very handy debugging tool.

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