Top C Programming Interview Questions & Answers:
Top C Programming Interview Questions & Answers: In this article, you will understand the questions you could expect at a fresher, intermediate, and advanced level. C is a high-level structured oriented programming language used for general-purpose programming requirements. It is also flexible to add user-defined functions. C Programming Interview Questions have been designed for Freshers and experienced candidates. Core Java Questions & Answers
1. What are the features of the C language?
Some features:
1. It is General-Purpose Language.
2. It is Simple And Efficient.
3. It is Procedural Language.
4. C language provides the feature of recursion.
5. C language is portable or Machine Independent.
6. C is a mid-level Programming Language.
7. Rich set of built-in Operators.
8. It has a function-rich library.
9. It is a structured Programming Language.
10. It has Dynamic Memory Management.
11. C is super fast.
12. It is extensible.
13. We can use pointers in C.
2. What is an array in C Language?
An array is a simple data structure that stores multiple elements of the same datatype in a reserved and sequential manner. The Elements of different data types must not be stored and each item can be accessed using the same name. An array must be declared before it is used. During declaration, the size of the array has to be specified.
There are 2 types of Initializations in C :
1.Compile Time: We can initialize the elements of arrays in the same way as the ordinary variables when they are declared.
2.Run Time: An array can be explicitly initialized at run time. This approach is usually applied for large arrays.
Types of arrays in C:
1. One Dimensional Array.
2. Two Dimensional Array.
3. Multi-Dimensional Array.
One Dimensional Array: An array that contains a finite number of data elements in a linear order.
Two-dimensional array: An array consisting of two subscripts is known as two-dimensional array.In two dimensional arrays the array is divided into rows and columns, i.e int arr[3][3].
In-multidimensional: Arrays are known as array of the arrays. In multidimensional arrays the array is divided into rows and columns, i.e int arr[3][3][3].
3. Difference between Arrays and pointers in C?
An array is a collection similar data type elements. whereas the pointer is a variable that stores the address of the variable. The arrays are static. Once the memory is allocated it cannot be resized or freed dynamically according to users requirement. Whereas Pointer is dynamic. The memory allocation can be resized or freed later at any time dynamically.
Arrays can be initialized at the definition, whereas pointers cannot be initialized at the definition. Arrays are allocated at compile time while pointers are allocated at runtime. Array is a group of elements (fixed size). whereas Pointer is not a group of elements. It is a single variable (Memory Address).
4. Difference between single-quotes(‘’) & double-quotes(“”) in C ?
In C/C++ Language, single-quoted variables are identified as the character(char value).Whereas double-quoted variables are identified as a string. In a string literal “x” is a string, it is containing character ‘x’ and a null terminator ‘\0’. So “x” is two-character array in this case.
In C the type of character literal is integer (int).Whereas in C++ the size of the character literal is char.So in C the sizeof(‘a’) is 4 for 32 bit architecture, and CHAR_BIT is 8. But the sizeof(char) is 1 byte for both C & C++.
For example:
Single quotes for character.
Double quotes for string.
printf(“%c \n”,’x’);
printf(“%s”,”Hello World”);
Output:
x
Hello World
C Programming Interview Questions & Answers:
5. What is Memory leak in C ?
The memory leak means when the programmers creates a memory in heap and forget to delete it. That memory is no longer in use by the program. It reduces the performance of the computer and reducing the amount of available memory. So that place is reserved for no reason. That’s why this is called the memory leak. To avoid this Always use memset along with malloc, or always use calloc and Make sure you are not accessing null pointer.
How to avoid memory leak in C?
There are many tools available to detect the memory leak. But we can also avoid the memory leak by using the free function like malloc or calloc.
6. What is difference between calloc() and malloc() in C ?
The calloc() and malloc() both are dynamic memory allocating functions.The dynamic memory allocation is manual allocation and freeing of memory according to programming needs.The dynamic memory is managed and served with pointers. The memory space was allocated in heap memory. You can create and destroy an array of elements dynamically at runtime.
malloc() function returns only starting address and does not make it zero on the other hand whereas calloc() function returns the starting address and make it zero. In malloc function, number of arguments is 1 while in calloc function, number of arguments is 2. malloc() is not secure as compared to calloc(). malloc does not initialize memory whereas calloc performs memory initialization.
What is malloc() : It is a function which is used to allocate a block of memory dynamically. It Allocates the memory of requested size and returns the pointer to the first byte of allocated space.
What is calloc() : Function is used to allocate multiple blocks of memory.It is a dynamic memory allocation function which is used to allocate the memory to complex data structures such as arrays and structures. It Allocates the space for elements of an array. Initializes the elements to zero and returns a pointer to the memory.
What is realloc() : It is used to modify the size of previously allocated memory space.
What is Free() : It Frees or empties the previously allocated memory space.
7. What is Dynamic memory allocation in C?
Dynamic memory allocation is a process of allocating memory space manually and freeing of memory at the execution time or at the run time. you can create and destroy an array of elements dynamically at runtime without any problems. There are some functions to allocate memory at run time.
malloc() : function is used for allocating block of memory at runtime.
This function reserves a block of memory of the given size and returns a pointer.
calloc() : is another memory allocation function that is used for allocating memory at runtime.
This function is normally used for allocating memory to derived data types such as arrays and structures.
realloc() : It is used to modify the size of previously allocated memory space.
Free() : It Frees or empties the previously allocated memory space.
8. What are the inbuilt functions for handling files in C?
fopen(): Function is used to create a new file or to open an existing file.
fclose(): Function is used to closes an opened file.
getw(): Function is used to read an integer value from a file.
putw(): Function is used to write an integer value to a file.
fgetc(): Function is used to read a single unsigned character from the input stream at the current position.
fputc(): Function is used to write a character to file.It outputs a character to a stream.
feof(): Function is used to find the end of a file(eof).
fgetchar(): Function is used to read a character from the keyboard.
fprintf(): Function is used to write a formatted data to the file.
fscanf(): Function is used to read a formatted data from the file.
fseek(): Function moves file pointer position to given location.
C Programming Interview Questions & Answers:
ftell(): Function is used to displays the current position of file pointer.
getc(): Function is used to read a character from the keyboard which does not display the entered value on screen and does not wait for the enter key.
getche(): Function is used to read a character from the keyboard which displays immediately on screen without waiting for the enter key.
getchar(): Function is used to reads a single character from the standard input stream.
putc(): Function is used to write a character to a file.
putchar(): Function is used to write a character to the screen.
printf(): Function is used to write a formatted data to screen.
sprinf(): Function is used to write a formatted output to string.
scanf(): Function is used to read a formatted data from the keyboard.
sscanf(): Function is used to Read the formatted input from a string.
remove(): Function is used to delete a file.
9. What is Type Casting in C Language?
Type Casting means converting one data type to another data type in C language. There are two ways to change the data. These are, the compiler will automatically change one data type into another data type and the programmer also change one data type into another data type. There are two types of type casting.
1.Implicit Type casting.
2.Explicit Type casting.
Implicit Type Conversion:
This type of conversion is performed automatically by the compiler is known as implicit type conversion or Automatic Type Conversion.
Explicit Type Conversion:
This type of conversion is performed by the programmer is known as explicit type conversion. The explicit type conversion is also known as type casting You can convert integer types to float.
You can convert float to double.
You can convert character to integer.
10. What is difference between While(1) and While(0)?
Loop:
A loop is used for executing a block of statements repeatedly until a given condition returns false.
While(1) Means an infinite loop which will run till a break statement occurs. Similarly, while(2,3,4…255) etc will all give infinite loops only.
While(0) Means non infinite loop where the condition is always treated as false and the code inside the block never gets to start executing.
11. Differentiate between call by value and call by reference in C ?
In call by value Does not allow you to make any changes in the actual variables.
In call by reference Allows you to make changes in the values of variables by using function calls.
In call by value, a copy of the variable is passed.
In call by reference, a variable itself is passed.
In call by value, actual and formal arguments will be created in different memory locations.
In call by reference, actual and formal arguments will be created in the same memory location.
In call by Value, Actual arguments remain safe, they cannot be modified accidentally.
In call by Reference, Actual arguments are not safe. They can be accidentally modified.
In call by value is the default method in programming languages like C++, C#, PHP, Visual Basic. etc..
In call by reference is supported only Java language.
In call by Value, variables are passed using a straightforward method
In call by Reference, pointers are required to store the address of variables.
12. What is a stack in C?
A stack is a linear data structure that follows the Last in, First out (LIFO) approach ( The elements always popped and pushed in the opposite order ) that means the element pushed first in the stack will be popped last will acquire top position in the stack and will pop first. A stack can be implemented using an array and linked list.
Basic operations in stack:
Push: This function adds an element to the top of the Stack.
Pop: This function removes the topmost element from the stack.
IsEmpty: Checks whether the stack is empty or not.
IsFull: Checks whether the stack is full or not.
Top: Displays the topmost element of the stack.
Traverse: This operation process all the elements present in stack exactly once.
Quit: Quit the stack
13. What do you mean by the pointer in C?
1. Pointers are the variables in C Language.
2. It store the address of another variable.
3. A pointer can also be used to refer to another pointer function.
4. We can return multiple values from a function using the pointer.
5. It allocates the memory for the variable at the run time.
6. The pointer might be of different data types such as int, char, float, double, etc.
7. Pointer reduces the code and it is used to retrieving strings, trees, etc.
8. The main purpose of pointer is to save memory space and achieve faster execution.
14. What is NULL Pointer in C Language?
Null pointer means not assigned any value, that means does not hold the address of any variables. But Null pointer has a reserved value that is called a null pointer. If you don’t have any address to be specified in the pointer at the time of declaration, you can assign NULL value. It will provide a better approach.
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