Comprehensive Guide to Common C Language Interview Questions and Concepts

The author presents a collection of 60 high‑frequency C language interview questions, aiming to help candidates prepare for technical interviews by covering core concepts and practical coding examples.

It begins with a brief definition of C as a general‑purpose, procedural language and lists essential keywords such as auto , break , int , return , etc.

Variable declaration and initialization are illustrated with examples like int age; float salary; char grade; followed by assignments age = 25; , salary = 2500.50; , and grade = 'A'; .

Pointers are introduced with int *ptr; and the address‑of operator, showing how to bind a pointer to a variable ( ptr = # ) and dereference it ( *ptr = 20; ).

Array usage and string handling are explained, including declarations ( int numbers[5]; ) and string literals ( char str[] = "Hello"; ), as well as standard library functions like strcpy , strcat , and strcmp .

Dynamic memory management is covered with malloc and free examples, demonstrating user‑driven allocation of an integer array, error checking for NULL , and proper deallocation.

Functions and recursion are discussed; a classic factorial function is shown, followed by a tail‑recursive version that passes an accumulator to avoid additional stack frames.

The article also reviews preprocessor directives ( #include , #define , conditional compilation with #ifdef / #ifndef ) and macro definitions such as #define PI 3.14159 and #define MAX(a,b) ((a) > (b) ? (a) : (b)) .

Additional topics include structures and unions, file I/O using fopen , fprintf , fread , and error handling strategies (return codes, errno , logging). The guide touches on bitwise operators, control flow statements, sorting algorithms, and basic concepts of OOP simulation in C.