Popular C Programming Interview Questions & Answers

C is a general-purpose, procedural programming language developed by Dennis Ritchie in 1972 at Bell Labs. It is widely used for developing system software, application software, and embedded firmware.

An array is a collection of elements of the same data type, stored in contiguous memory locations and accessed using an index or a subscript.

printf() is used for output (printing to the console), whereas scanf() is used for input (reading from the console).

A pointer is a variable that stores the address of another variable in C programming.

Dereferencing a pointer means accessing the value stored at the memory address pointed to by the pointer variable.

Both functions are used for dynamic memory allocation. malloc() allocates uninitialized memory, while calloc() allocates initialized memory (sets all bits to zero).

The size of operator is used to determine the size (in bytes) of a data type or a variable.

Both ++i and i++ increment the variable i by 1. However, ++i is pre-increment (increments the value before using it in an expression) whereas i++ is post-increment (uses the current value in an expression and then increments it).

The const keyword is used to define constants. It specifies that the value of the variable cannot be changed after initialization.

In C, = is the assignment operator used to assign a value to a variable. == is the equality operator used to compare two values for equality. === is not a valid operator in C.

Recursion is the process in which a function calls itself directly or indirectly. It is often used for solving problems that can be broken down into smaller subproblems of the same type.

 The break statement is used to exit the loop prematurely, whereas the continue statement is used to skip the rest of the loop’s code and move to the next iteration.

There are three types of loops in C: for loop, while loop, and do-while loop.

The switch statement is used to make decisions based on the value of a variable. It evaluates the expression and matches the value with different case labels. If a match is found, the corresponding block of code is executed.

The #include directive is used to include the contents of a file in the source code. It is commonly used to include header files in C programs.

Local variables are declared inside a function and are only accessible within that function, whereas global variables are declared outside of any function and can be accessed by any function in the program.

A structure is a user-defined data type that allows grouping variables of different data types under a single name. It is used to represent a record.

The -> operator is used to access members of a structure through a pointer to that structure.

C supports four storage classes: auto, register, static, and extern, each with different scopes and lifetimes.

File handling in C involves operations such as opening, reading, writing, closing, and manipulating files. It is done using FILE pointers and functions like fopen(), fprintf(), fscanf(), fclose(), etc.

The fgets() function is used to read a string from a file or the standard input (keyboard) along with newline characters.

Dynamic memory allocation allows a program to allocate memory at runtime using functions like malloc(), calloc(), and realloc(). It helps in managing memory efficiently.

The typedef keyword is used to create aliases for data types, making it easier to define complex data structures and improving code readability.

Bitwise operators manipulate individual bits of a variable. The bitwise operators in C are & (AND), | (OR), ^ (XOR), ~ (NOT), << (left shift), and >> (right shift).

Both union and structure are used to group variables, but a structure allocates memory for all its variables, whereas a union allocates memory only for the largest variable in it. Thus, union saves memory by allowing the same memory location to be used for different variables at different times.

A const pointer is a pointer that points to a constant value, and it cannot be used to modify the value it points to.

Function pointers are pointers that point to the address of functions. They can be used to call functions indirectly through the pointer variable.

The assert() function is used for debugging purposes. If the expression passed to assert() evaluates to false, the program terminates and an error message is displayed.

Recursion is a programming technique where a function calls itself directly or indirectly to solve a problem. It is particularly useful for tasks that can be broken down into smaller, similar subproblems.

The volatile keyword is used to indicate to the compiler that a variable’s value can be changed by external factors, such as an interrupt service routine. It prevents the compiler from optimizing away code that uses the variable.