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Pointers in C Interview Questions & Answers - Learning Mode

Pointers in C Interview Questions & Answers - Learning Mode

A pointer is a variable which contains the address in memory of another variable. We can have a pointer to any variable type. The unary or monadic operator & gives the ``address of a variable''. The indirection or dereference operator * gives the ``contents of an object pointed to by a pointer''. A pointer is a variable whose value is the address of another variable, i.e., direct address of the memory location. Like any variable or constant, you must declare a pointer before using it to store any variable address.

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Pointers in C Interview Questions & Answers - Learning Mode
Try Pointers in C Interview Questions & Answers - Exam Mode
Question: Difference between arrays and pointers?

Answer: Pointers are used to manipulate data using the address. Pointers use * operator to access the data pointed to by them<br><br>Arrays use subscripted variables to access and manipulate data.Array variables can be equivalently written using pointer expression. Source:
Question: What is the difference between far and near?

Answer: Some compilers for PC compatibles use two types of pointers.
near pointers are 16 bits long and can address a 64KB range. far pointers are 32 bits long and can address a 1MB range.

Near pointers operate within a 64KB segment. There?s one segment for function addresses and one segment for data. far pointers have a 16-bit base (the segment address) and a 16-bit offset. The base is multiplied by 16, so a far pointer is effectively 20 bits long. Before you compile your code, you must tell Source:
Question: When should a far pointer be used?

Answer: Sometimes you can get away with using a small memory model in most of a given program. There might be just a few things that don?t fit in your small data and code segments. When that happens, you can use explicit far pointers and function declarations to get at the rest of memory. A far function can be outside the 64KB segment most functions are shoehorned into for a small-code model. (Often, libraries are declared explicitly far, so they?ll work no matter what code model the program uses.)
A Source:
Question: What does it mean when a pointer is used in an if statement?

Answer: Any time a pointer is used as a condition, it means ?Is this a non-null pointer?? A pointer can be used in an if, while, for, or do/while statement, or in a conditional expression. Source:
Question: When would you use a pointer to a function?

Answer: Pointers to functions are interesting when you pass them to other functions. A function that takes function pointers says, in effect, ?Part of what I do can be customized. Give me a pointer to a function, and I?ll call it when that part of the job needs to be done. That function can do its part for me.? This is known as a ?callback.? It?s used a lot in graphical user interface libraries, in which the style of a display is built into the library but the contents of the display are part of the ap Source:
Question: What are the disadvantages of using Pointers.

Answer: when we are using pointers the main disadvantages is that,the hacker can easily to identified address of the source code and change source code.
Another one is that to distributing of data base is difficult when it is in the server. Source:
Question: What do you mean by normalisation of pointers

Answer: Normalization functions are provided which take any of these combined types as their first argument, a pointer to the same combined type as their second argument, and place the normalization of the first into the second. Source:
Question: What is :- pointer , NULL pointer , dangling pointer , far pointer , near pointer , huge pointer , generic pointer , smart pointer ?

Answer: A null pointer has a reserved value, often but not necessarily the value zero, indicating that it refers to no object.
In most C programming environments malloc returns a null pointer if it is unable to allocate the memory region requested, which notifies the caller that there is insufficient memory available.

Dangling pointers and wild pointers in computer programming are pointers that do not point to a valid object of the appropriate type. Dangling pointers arise when an object is de Source:
Question: Why should we assign NULL to the elements (pointer) after freeing them?

Answer: This is paranoia based on long experience. After a pointer has been freed, you can no longer use the pointed-to data. The pointer is said to ?dangle?; it doesn?t point at anything useful. If you ?NULL out? or ?zero out? a pointer immediately after freeing it, your program can no longer get in trouble by using that pointer. True, you might go indirect on the null pointer instead, but that?s something your debugger might be able to help you with immediately. Also, there still might be copies of th Source:
Question: Difference between :- 1) NULL pointer and NULL macro ?

Answer: Both are very different.
NULL macro is
#define NULL 0
it means the macro NULL will be replaced by 0 while preprocessing
But the NULL pointer means it points to nowhere i.e. contains 0.
It contains 0 means it may be dangerous to use such pointer without assigning proper address to it otherwise NULL pointer may try to access reset address may cause the program to crash. Source:
Question: How I can add two numbers in c language without using Arithmetic operators?

Answer: by using bitwise operators it is possible, for example a=8,ie in binary(00001000) & b=4 in binary (00000100)if we add a,b then we get 12 in binary(00001100)..if u add the binary a,b & convert the answer in to decimal we get 12.. in the c code is:
void main()
int a=8,b=4,c;
so,by using ^ operator we can do th Source:
Question: What is file pointer and its working method?

Answer: when a pointer is pointing to the address of a file than it is called as a file pointer.
for example:
FILE *fp;
here in above statement we are declaring a file pointer.
there are many modes of opening a file.they are read ,write,append ..
they are as follows..
above statement is opening a file in read mode..

Question: How many levels of pointers can you have?

Answer: The answer depends on what you mean by ?levels of pointers.? If you mean ?How many levels of indirection can you have in a single declaration?? the answer is ?At least 12.?

int i = 0;
int *ip01 = & i;
int **ip02 = & ip01;
int ***ip03 = & ip02;
int ****ip04 = & ip03;
int *****ip05 = & ip04;
int ******ip06 = & ip05;
int *******ip07 = & ip06;
int ********ip08 = & ip07;
int *********ip09 = & ip08;
int **********ip10 = & ip09;
int ***********ip11 = & ip10;
i Source:
Question: What is a ?null pointer assignment? error? What are bus errors, memory faults, and core dumps?

Answer: These are all serious errors, symptoms of a wild pointer or subscript.

Null pointer assignment is a message you might get when an MS-DOS program finishes executing. Some
such programs can arrange for a small amount of memory to be available ?where the NULL pointer points to? (so to speak). If the program tries to write to that area, it will overwrite the data put there by the compiler.

When the program is done, code generated by the compiler examines that area. If that data has Source:
Question: Are pointers integers?

Answer: No, pointers are not integers.A pointer is an address.It is merely a positive number and not an integer. Source:
Question: What is indirection?

Answer: 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. Source:
Question: Is **p and &(*p) same?

Answer: No both are not equal.**p s pointer to another pointer where as &(*P) is equal to p.. Source:
Question: What is a null pointer?

Answer: There are times when it?s necessary to have a pointer that doesn?t point to anything. The macro NULL, defined in <stddef.h>, 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:

1) To stop indirection in a recursive data structure

2) As an error value

3) As a sentinel value Source:
Question: what is the difference between near pointer and far pointer?

Answer: Near is 16 bit long, Far is 32 bit long.
near ptr can't have different SEGMENTs and SHIFTS to point to same memory location. Far has this property. Source:
Question: What is a null pointer ?

Answer: 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:

1) To stop indirection in a recursive data structure.
2) As an error value.
3) As a sentinel value. Source:

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