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C Programming Questions

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1. What is the C programming language?

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C is a powerful, general-purpose, and procedural programming language. It is often called a "middle-level" language because it combines the features of high-level languages (like structured control) with the ability to directly manipulate memory (like low-level assembly).

Added: Nov 30, 2025

2. Who designed and developed C?

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The C programming language was designed and first implemented by Dennis Ritchie at Bell Labs between 1972 and 1973.

Added: Nov 30, 2025

3. When was C invented?

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C was developed in the early 1970s (specifically, 1972-1973). It was primarily created to develop the UNIX operating system.

Added: Nov 30, 2025

4. How does C differ from purely high-level languages like Python or Java?

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The key difference is C's use of pointers and its need for explicit memory management. C is compiled directly into machine code, offering superior execution speed and direct control over hardware, which is often abstracted away in higher-level, interpreted languages.

Added: Nov 30, 2025

5. Name three major applications or systems that rely on C.

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1. Operating System Kernels (e.g., Linux, macOS, and parts of Windows). 2. Database Systems (e.g., MySQL, PostgreSQL). 3. Compilers, Interpreters, and Assemblers for other programming languages.

Added: Nov 30, 2025

6. What is the significance of the main() function in a C program?

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The execution of every C program always starts and ends with the main() function. It serves as the entry point for the operating system to run the program.

Added: Nov 30, 2025

7. What is the primary role of a "header file" (e.g., <stdio.h>)?

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A header file contains function declarations, macro definitions, and constants. When you #include a header, you tell the compiler to make those resources (like the printf() function in <stdio.h>) available to your program.

Added: Nov 30, 2025

8. What is the primary difference between a compiler and an interpreter?

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A compiler translates the entire source code into machine code before execution, while an interpreter translates and executes code line by line.

Added: Nov 30, 2025

9. What is the significance of the `main()` function in a C program?

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Execution of a C program always begins and ends with the `main()` function.

Added: Nov 30, 2025

10. What is the purpose of the `#include <stdio.h>` statement?

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It includes the standard input/output header file, which provides functions like `printf()` and `scanf()`.

Added: Nov 30, 2025

11. Explain the difference between call by value and call by reference in C.

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Call by value passes a copy of the argument's value, while call by reference passes the address of the argument, allowing the function to modify the original variable.

Added: Nov 30, 2025

12. What is a variable in C?

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A variable is a name given to a memory location that stores a piece of data. Its value can change during program execution.

Added: Nov 30, 2025

13. List three basic data types in C.

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Integer (`int`), Floating-point (`float`), and Character (`char`).

Added: Nov 30, 2025

14. What is the default initial value of a local variable in C?

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The initial value of a local variable is garbage (an unpredictable, unknown value).

Added: Nov 30, 2025

15. What is the difference between the `=` operator and the `==` operator?

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The `=` operator is used for assignment, while the `==` operator is used for comparison (checking if two values are equal).

Added: Nov 30, 2025

16. What is type casting in C?

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Type casting is the process of converting a variable or expression from one data type to another.

Added: Nov 30, 2025

17. What are the two main types of loops in C for repetition?

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Entry-controlled loops (like `for` and `while`) and exit-controlled loops (like `do-while`).

Added: Nov 30, 2025

18. Explain the use of the `break` statement in a loop.

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The `break` statement is used to immediately terminate the innermost loop or switch statement.

Added: Nov 30, 2025

19. Explain the use of the `continue` statement in a loop.

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The `continue` statement is used to skip the rest of the current iteration of a loop and proceed to the next iteration.

Added: Nov 30, 2025

20. What is an array in C?

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An array is a collection of similar data elements stored at contiguous memory locations, referenced by a single name.

Added: Nov 30, 2025

21. How is the size of an array fixed in C?

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The size of an array is fixed at compile time (or declaration time) and cannot be changed later.

Added: Nov 30, 2025

22. What is a string in C?

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A string in C is an array of characters terminated by a null character (\0).

Added: Nov 30, 2025

23. What header file must be included to use string manipulation functions like `strlen()` and `strcpy()`?

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The `<string.h>` header file.

Added: Nov 30, 2025

24. What is a pointer in C?

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A pointer is a variable that stores the memory address of another variable.

Added: Nov 30, 2025

25. What is the dereference operator in C, and what does it do?

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The dereference operator is `*`. It is used to access the value stored at the memory address held by a pointer.

Added: Nov 30, 2025

26. What is the address-of operator in C, and what does it do?

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The address-of operator is `&`. It is used to get the memory address of a variable.

Added: Nov 30, 2025

27. What is a NULL pointer?

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A NULL pointer is a pointer that points to no memory location. It is initialized with the value 0 or NULL.

Added: Nov 30, 2025

28. What is a structure (`struct`) in C?

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A structure is a user-defined data type that allows you to combine data items of different data types under a single name.

Added: Nov 30, 2025

29. What is a union in C?

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A union is similar to a structure, but all members of a union share the same memory location. Only one member can hold a value at any given time.

Added: Nov 30, 2025

30. What is the primary difference between `struct` and `union` in terms of memory?

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In a `struct`, memory is allocated for all members separately. In a `union`, all members share the memory of the largest member.

Added: Nov 30, 2025

31. What is the purpose of the `typedef` keyword?

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The `typedef` keyword is used to give a new name (an alias) to an existing data type or user-defined type (like a structure).

Added: Nov 30, 2025

32. What is recursion in C?

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Recursion is the process where a function calls itself, either directly or indirectly, until a base condition is met.

Added: Nov 30, 2025

33. What is a header file in C?

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A header file contains function declarations, macros, and constant definitions that can be included in a C program using the `#include` directive.

Added: Nov 30, 2025

34. What is the role of the `sizeof()` operator?

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

Added: Nov 30, 2025

35. What is a preprocessor directive?

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A preprocessor directive is an instruction given to the C preprocessor (e.g., `#include`, `#define`) that is executed before the actual compilation process begins.

Added: Nov 30, 2025

36. What is a macro in C?

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A macro is a piece of code that is given a name. Whenever the name is used, the preprocessor replaces it with the actual code.

Added: Nov 30, 2025

37. What is the difference between a global variable and a local variable?

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A global variable is declared outside all functions and is accessible from anywhere. A local variable is declared inside a function and is only accessible within that function.

Added: Nov 30, 2025

38. What are storage classes in C?

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Storage classes define the scope, visibility, and lifetime of a variable, such as `auto`, `extern`, `static`, and `register`.

Added: Nov 30, 2025

39. What is the use of the `static` storage class?

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The `static` storage class retains the value of a variable between function calls and restricts its scope to the file or function where it is declared.

Added: Nov 30, 2025

40. What is the purpose of the `extern` keyword?

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The `extern` keyword is used to declare a global variable or function that is defined in another file, making it accessible across multiple source files.

Added: Nov 30, 2025

41. What is dynamic memory allocation in C?

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Dynamic memory allocation is the process of allocating memory manually during runtime using functions like `malloc()`, `calloc()`, and `realloc()`.

Added: Nov 30, 2025

42. Which function is used to free dynamically allocated memory?

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The `free()` function is used to deallocate (release) the memory previously allocated by `malloc`, `calloc`, or `realloc`.

Added: Nov 30, 2025

43. What is the difference between `malloc()` and `calloc()`?

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`malloc()` allocates a single block of requested memory and returns a garbage value. `calloc()` allocates memory for a specified number of blocks and initializes all bytes to zero.

Added: Nov 30, 2025

44. What is file handling in C?

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File handling refers to the mechanism that allows a program to read data from a file stored on disk or write data to a file.

Added: Nov 30, 2025

45. What is the file pointer (`FILE *`) used for in file handling?

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It is a structure pointer that points to the structure containing all the information about the file, such as its name, location, and reading/writing status.

Added: Nov 30, 2025

46. Which function is used to open a file in C?

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The `fopen()` function, which takes the file path and the mode (e.g., "r" for read, "w" for write) as arguments.

Added: Nov 30, 2025

47. What is the significance of the `void` keyword in C?

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It indicates that a function does not return any value, or that a function accepts no arguments, or it can be used for generic pointers (`void *`).

Added: Nov 30, 2025

48. What is a dangling pointer?

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A dangling pointer is a pointer that points to a memory location that has been deallocated (freed), but the pointer still holds the old address.

Added: Nov 30, 2025

49. What is the scope of a variable?

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The scope of a variable defines the region of the program where the variable can be accessed or seen.

Added: Nov 30, 2025

50. What is an L-value and an R-value?

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An L-value is an expression that has an address (like a variable name), and an R-value is an expression that has a value but no fixed address (like a constant).

Added: Nov 30, 2025

51. What is the purpose of the `goto` statement?

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The `goto` statement is used to transfer control unconditionally from one part of the program to a labeled statement elsewhere in the same function.

Added: Nov 30, 2025

52. What is the difference between `getc()` and `getchar()`?

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`getc()` reads a character from a specified file stream, while `getchar()` specifically reads a character from the standard input (`stdin`).

Added: Nov 30, 2025

53. What are the conditional operators (ternary operator) in C?

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The conditional operators are `? :` (e.g., `condition ? expression_if_true : expression_if_false`).

Added: Nov 30, 2025

54. What is the associativity of the assignment operator (`=`)?

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The assignment operator has right-to-left associativity.

Added: Nov 30, 2025

55. What is an enumeration (`enum`) in C?

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An enumeration is a user-defined data type that consists of integral constants, where each constant is given a descriptive name.

Added: Nov 30, 2025

56. What does the term "portability" mean in C programming?

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Portability refers to the ability of a C program to be compiled and run on different computer systems or operating systems with little to no modification.

Added: Nov 30, 2025

57. How does the C language treat the logical value true?

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The logical value true is represented by any non-zero integer value (usually 1).

Added: Nov 30, 2025

58. How does the C language treat the logical value false?

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The logical value false is represented by the integer value 0.

Added: Nov 30, 2025

59. What is a multidimensional array?

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A multidimensional array is an array of arrays, most commonly used as a 2D array (a table with rows and columns).

Added: Nov 30, 2025

60. In a function prototype, why is it acceptable to omit parameter names?

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The compiler only requires the data types of the parameters to ensure proper function calling, so the names are optional.

Added: Nov 30, 2025

61. What is an inline function?

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An inline function is a function whose code is substituted directly at the point of call during compilation, saving the overhead of a regular function call.

Added: Nov 30, 2025

62. What is the escape sequence for a newline character?

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The escape sequence for a newline character is `\n`.

Added: Nov 30, 2025

63. What is the escape sequence for the null character?

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The escape sequence for the null character is `\0`.

Added: Nov 30, 2025

64. How do you represent a single quote character in a C string literal?

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You use the escape sequence `\'` (backslash followed by a single quote).

Added: Nov 30, 2025

65. What is the difference between `printf()` and `puts()`?

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`printf()` is used for formatted output and does not automatically add a newline. `puts()` prints a string and automatically adds a newline character at the end.

Added: Nov 30, 2025

66. What is the purpose of the `fflush()` function?

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The `fflush()` function is used to clear (flush) the output buffer of a stream, forcing any buffered data to be written immediately.

Added: Nov 30, 2025

67. What is the meaning of the file opening mode "a" in `fopen()`?

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The "a" stands for append mode. It opens a file for writing, and all new data is added to the end of the file.

Added: Nov 30, 2025

68. What is an infinite loop?

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An infinite loop is a loop whose condition never becomes false, causing it to execute continuously until the program is manually terminated.

Added: Nov 30, 2025

69. What is the function of the `default` case in a `switch` statement?

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The `default` case is executed when none of the specified `case` conditions match the expression value.

Added: Nov 30, 2025

70. Can a C function return multiple values?

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No, a C function can only return one value directly. To return multiple values, you must use pointers or structures.

Added: Nov 30, 2025

71. What is a nested loop?

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A nested loop is a loop inside another loop. The inner loop executes completely for every single execution of the outer loop.

Added: Nov 30, 2025

72. What are command-line arguments in C?

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Command-line arguments are data passed to the main function of a program when it is executed from the command line, received via `argc` and `argv`.

Added: Nov 30, 2025

73. What is the data type of the `argv` parameter in the `main` function?

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The `argv` parameter is an array of strings (or `char *argv[]`).

Added: Nov 30, 2025

74. What is the meaning of the `const` keyword in C?

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The `const` keyword is used to declare a variable as a constant, meaning its value cannot be changed after initialization.

Added: Nov 30, 2025

75. What is a constant (literal) in C?

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A constant is a value that cannot be changed during the execution of a program.

Added: Nov 30, 2025

76. What is the difference between a constant and a variable in terms of modification?

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A variable's value can be changed, while a constant's value is fixed and cannot be modified.

Added: Nov 30, 2025

77. What are operators in C?

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Operators are symbols that tell the compiler to perform specific mathematical, relational, or logical operations.

Added: Nov 30, 2025

78. List three types of relational operators in C.

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Greater than (`>`), Less than (`<`), Equal to (`==`), or Not equal to (`!=`). (Any three are acceptable).

Added: Nov 30, 2025

79. What is a bitwise operator?

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A bitwise operator works on individual bits of its operands (e.g., AND `&`, OR `|`, XOR `^`).

Added: Nov 30, 2025

80. What is operator precedence?

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Operator precedence determines the order in which operators in an expression are evaluated.

Added: Nov 30, 2025

81. What is the purpose of using parentheses `()` in an expression?

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Parentheses are used to group terms and override the default operator precedence.

Added: Nov 30, 2025

82. What is the use of the `_Bool` data type (or `bool` in C99)?

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The `_Bool` data type is used to store boolean values, which can only be `true` (1) or `false` (0).

Added: Nov 30, 2025

83. What is the function of the `exit()` function?

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The `exit()` function is used to terminate the execution of the entire C program immediately, regardless of where it is called.

Added: Nov 30, 2025

84. What header file must be included to use the dynamic memory allocation functions?

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The `<stdlib.h>` header file.

Added: Nov 30, 2025

85. What does the acronym K&R C refer to?

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K&R C refers to the original specification of the C language as described in "The C Programming Language" book by Kernighan and Ritchie.

Added: Nov 30, 2025

86. What is the purpose of the semicolon `;` in C?

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The semicolon is used to mark the end of a statement.

Added: Nov 30, 2025

87. What is the maximum size of a `char` data type?

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A `char` data type is typically 1 byte (8 bits).

Added: Nov 30, 2025

88. What is the main advantage of using an array instead of individual variables?

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Arrays allow you to manage and process a large number of related variables efficiently using loops and indexing.

Added: Nov 30, 2025

89. How do you access the elements of a structure?

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Elements of a structure are accessed using the dot (`.`) operator (for a structure variable) or the arrow (`->`) operator (for a structure pointer).

Added: Nov 30, 2025

90. What is the correct format specifier for printing a `float` value?

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The correct format specifier is `%f`.

Added: Nov 30, 2025

91. What is the correct format specifier for printing an `int` value?

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The correct format specifier is `%d` or `%i`.

Added: Nov 30, 2025

92. What is the correct format specifier for printing a pointer address?

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The correct format specifier is `%p`.

Added: Nov 30, 2025

93. In `scanf()`, what is the purpose of the address-of operator (`&`)?

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It passes the memory address of the variable to `scanf()`, allowing the function to store the input value directly into that variable.

Added: Nov 30, 2025

94. What is the difference between `gets()` and `fgets()`?

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`gets()` reads an entire line from standard input but is unsafe as it has no buffer size limit. `fgets()` is safer as it takes a buffer size limit and specifies the input stream.

Added: Nov 30, 2025

95. What is the advantage of using `register` variables?

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They suggest to the compiler that the variable should be stored in a CPU register for faster access, though the compiler may ignore the suggestion.

Added: Nov 30, 2025

96. Can a C program be compiled without the `main()` function?

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Yes, it can be compiled, but it cannot be executed without a definition for the `main()` function.

Added: Nov 30, 2025

97. What is the role of `argc` in command-line arguments?

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`argc` (argument count) is an integer that stores the total number of command-line arguments passed to the program.

Added: Nov 30, 2025

98. What is the largest integer type in C?

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The `long long int` or `long long` type (C99 standard or later).

Added: Nov 30, 2025

99. What is a dangling `else` problem?

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It is a common ambiguity in programming where it is unclear which `if` statement an `else` clause belongs to. In C, the `else` always binds to the nearest preceding unmatched `if`.

Added: Nov 30, 2025

100. What is a function prototype?

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A function prototype is a declaration of a function that specifies the function's name, return type, and parameter types, allowing the compiler to perform type checking.

Added: Nov 30, 2025

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