Top C Language Interview Questions & Answers (2026)
📘 Beginner
40 Questions
🎯 Fresher Friendly
🕒 Updated Mar 2026
C is a general-purpose, procedural programming language developed by Dennis Ritchie at Bell Labs in 1972.
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C language was developed by Dennis Ritchie at Bell Laboratories in 1972.
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C is fast, portable, structured, supports pointers, dynamic memory allocation, and provides low-level access to memory.
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C is a procedural language, while C++ supports both procedural and object-oriented programming.
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Data types define the type of data a variable can hold, such as int, float, char, double, and void.
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A variable is a named location in memory used to store data.
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Local variables are declared inside functions and have limited scope, while global variables are declared outside all functions and are accessible anywhere in the program.
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A constant is a variable whose value cannot be changed during program execution.
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printf() is used to display output on the screen.
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scanf() is used to take input from the user.
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A function is a block of code that performs a specific task and can be reused.
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main() is the entry point of every C program where execution starts.
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Header files contain function declarations and macros. Example: stdio.h, stdlib.h, math.h.
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Call by value passes a copy of the variable, while call by reference passes the address of the variable.
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Pointers are variables that store the memory address of another variable.
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A NULL pointer is a pointer that does not point to any valid memory location.
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A dangling pointer points to a memory location that has been freed or deleted.
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A structure is a user-defined data type in C that groups related variables of different data types.
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In structure, each member has its own memory, while in union, all members share the same memory space.
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An array is a collection of elements of the same data type stored in contiguous memory locations.
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A string is a sequence of characters terminated by a null character (\0).
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Loops are used to execute a block of code repeatedly. Types: for, while, do-while.
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while checks the condition before execution, do-while checks after execution (executes at least once).
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Recursion is a process where a function calls itself.
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A loop that never terminates because its condition always remains true.
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break exits the loop immediately, while continue skips the current iteration.
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A pointer to a pointer stores the address of another pointer variable.
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Dynamic memory allocation allows programs to request memory during runtime using malloc(), calloc(), realloc(), and free().
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malloc() dynamically allocates memory and returns a void pointer to it.
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calloc() allocates multiple blocks of memory and initializes them with zero.
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realloc() changes the size of previously allocated memory block.
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free() deallocates dynamically allocated memory to prevent memory leaks.
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Preprocessor directives are commands that are processed before the program is compiled (e.g., #include, #define).
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Type casting is converting a variable from one data type to another.
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sizeof is used to determine the size (in bytes) of a data type or variable.
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== is a comparison operator, while = is an assignment operator.
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Storage classes define scope, lifetime, and visibility of variables: auto, static, extern, register.
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The static keyword preserves the value of a variable across function calls.
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return sends control back from a function, while exit() terminates the entire program.
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