Top 150 C Interview Questions and Answers

This is a programming question involving preprocessor directives and printf function.

• The preprocessor directives #define a 3+3 and #define b 11-3 will be replaced by their respective values during compilation.

• The main function will print the result of a*b, which is equivalent to 6*8.

• Therefore, the output will be 48.

• The printf function will print the integer value of 48.

Continue statement skips the current iteration of a loop and moves to the next one, while break statement terminates the loop.

• Continue statement is used to skip a particular iteration of a loop and move to the next one.

• Break statement is used to terminate the loop and move to the next statement outside the loop.

• Continue statement is used when we want to skip a particular iteration of a loop based on some condition.

• Break statement is used when we want to terminate the loop bas...read more

Data type is a classification of data items based on the type of value they hold. C programming has various data types.

• Data type determines the type of data that can be stored in a variable

• C programming has basic data types like int, float, char, double, etc.

• C programming also has derived data types like arrays, pointers, structures, unions, etc.

Yes, it is possible to compile a C program without main().

• A C program must have a main() function as the entry point.

• However, it is possible to compile a C program without a main() function using a different entry point.

• This can be achieved by defining a different entry point using linker options or compiler-specific attributes.

• For example, in some embedded systems, the entry point may be defined as _start() instead of main().

malloc and calloc are functions used for dynamic memory allocation in C programming language.

• malloc() allocates a block of memory of specified size and returns a pointer to the first byte of the allocated memory.

• calloc() allocates a block of memory of specified size and initializes all the bytes to zero.

• Both functions are used to allocate memory dynamically during runtime.

• The memory allocated by these functions must be freed using the free() function to avoid memory leaks.

C is a programming language and does not have a fixed number of bits.

• C is a high-level programming language that can be compiled to run on different architectures with varying bit sizes.

• The number of bits in C depends on the hardware architecture it is compiled for.

• For example, C code compiled for a 32-bit architecture will have 32-bit integers, while code compiled for a 64-bit architecture will have 64-bit integers.

In C programming, # stands for preprocessor directive.

• The # symbol is used to indicate a preprocessor directive in C programming.

• Preprocessor directives are instructions to the compiler that are executed before the compilation process.

• They are used to include header files, define constants, perform conditional compilation, etc.

• Examples of preprocessor directives include #include, #define, #ifdef, #ifndef, etc.

ISR routine is a function that is executed in response to an interrupt signal.

• ISR stands for Interrupt Service Routine

• It is used to handle hardware interrupts

• ISR routines are written in C language

• They are executed when an interrupt signal is received

• ISR routines should be short and efficient

• They should not block other interrupts

• Examples of ISR routines include handling keyboard input or timer interrupts

C is a prominent programming language used for system programming and developing operating systems.

• C was developed by Dennis Ritchie at Bell Labs in 1972.

• It is a compiled language and is known for its efficiency and low-level memory manipulation capabilities.

• C is used for system programming, developing operating systems, embedded systems, and game development.

• Some popular software written in C include the Linux kernel, MySQL, and Adobe Photoshop.

• C++ and Objective-C are both d...read more

C program for finding greatest of 3 numbers and finding a number in a string. RTOs related questions.

• For finding greatest of 3 numbers, use if-else statements and compare each number with the other two.

• For finding a number in a string, use string manipulation functions like strstr() or atoi().

• For RTOs related questions, brush up on traffic rules and regulations specific to your region.

Yes, I have made a thread-based program in C.

• Threads in C allow for concurrent execution of multiple tasks.

• Threads can be created using the pthread library in C.

• Thread-based programs can improve performance and responsiveness.

• Example: Creating multiple threads to perform parallel processing tasks.

WAP in C to find the reverse of a number

• Take input number from user

• Initialize a variable to store the reverse of the number

• Use a while loop to extract the last digit of the number and add it to the reverse variable

• Divide the number by 10 to remove the last digit

• Repeat until the number becomes 0

• Print the reverse of the number

Dynamic Array in C - Implement a dynamic array to store strings in C language.

• Use malloc() to allocate memory for the array.

• Use realloc() to resize the array when needed.

• Use strcpy() to copy strings into the array.

• Use free() to deallocate memory when done.

C is a general-purpose, procedural programming language.

• C was developed by Dennis Ritchie at Bell Labs in 1972.

• It is widely used for system programming, embedded systems, and game development.

• C is a compiled language and has a low-level memory manipulation feature.

• It has influenced many other programming languages such as C++, Java, and Python.

Program to print 'Hello, World!' in C language

• Include stdio.h header file

• Use printf() function to print the message

• End the program with return 0 statement

This C program selects a contiguous subarray of size m from an array with the sum closest to zero.

• Iterate through the array and calculate the sum of each subarray of size m

• Keep track of the subarray with the closest sum to zero

• Return the subarray with the closest sum to zero

calloc() and malloc() are both used for dynamic memory allocation in C, but calloc() also initializes the allocated memory to zero.

• calloc() allocates memory for an array of elements and initializes them to zero.

• malloc() only allocates memory for the specified number of bytes.

• calloc() is useful when initializing arrays or structures.

• malloc() is useful when allocating memory for a single variable or a dynamically sized array.

Memory layout in C refers to the organization of memory for variables and data structures.

• Memory is divided into 3 sections: Text segment, Data segment, and Heap segment.

• Text segment contains the executable code.

• Data segment contains global and static variables.

• Heap segment contains dynamically allocated memory.

• Stack segment contains function calls and local variables.

There is no OOP language in C, but C++ is an OOP language that is derived from C.

• C++ is an extension of C that supports OOP concepts like encapsulation, inheritance, and polymorphism.

• C++ allows the creation of classes and objects, which are the building blocks of OOP.

• C++ also supports features like templates, exceptions, and namespaces that make it a powerful language for software development.

The question seems to be related to the chemical composition of a material.

• The material contains 25% Mn, 60%+ Si, 20-30% S, and 40% P.

• The total percentage of S and P in the material is 75%.

• The material may be used in the manufacturing of steel or other alloys.

• The inspector should be familiar with the chemical properties of the material and its intended use.

Data structure in C refers to the way data is organized and stored in memory.

• Data structures in C provide efficient ways to store and manipulate data.

• Examples of data structures in C include arrays, linked lists, stacks, queues, and trees.

• Data structures help optimize memory usage and improve program efficiency.

• They enable efficient searching, sorting, and retrieval of data.

• Understanding data structures is crucial for developing efficient software applications in C.

C programming language is a high-level programming language used for system programming and developing applications.

• C is a compiled language

• It is a procedural language

• C has a rich library of built-in functions

• C is used for developing operating systems, compilers, and embedded systems

• C is known for its efficiency and speed

• C supports pointers and memory management

• C is widely used in the development of games and other high-performance applications

C program is a computer program written in the C programming language.

• C is a high-level programming language.

• C programs are compiled using a compiler.

• C programs are used to develop operating systems, software applications, and embedded systems.

• C programs use variables, data types, control structures, and functions.

• Example: Hello World program in C.

C is a programming language used for system programming, embedded systems, and game development.

• C was developed by Dennis Ritchie at Bell Labs in 1972.

• It is a compiled language, meaning that the code is translated into machine-readable instructions before execution.

• C is known for its efficiency and low-level control over hardware, making it a popular choice for operating systems and device drivers.

• C functions are defined with a return type, name, and parameters, and can be ca...read more

A null pointer points to nothing while a void pointer can point to any data type.

• A null pointer is a pointer that has been explicitly set to a null value.

• A void pointer is a pointer that has no type associated with it.

• A null pointer is a subtype of a void pointer.

• A null pointer is used to indicate that a pointer does not point to a valid object.

• A void pointer is used to store a pointer to any type of object.

Program to swap two variables without using a third variable.

• Use arithmetic operations to swap the values

• Use XOR operator to swap the values

• Use tuple packing and unpacking to swap the values

C is a programming language developed by Dennis Ritchie in 1972.

• C is a general-purpose programming language

• It is widely used for system programming, embedded systems, and game development

• C is a compiled language, meaning that the code needs to be compiled before it can be executed

• It is known for its efficiency and low-level programming capabilities

• C has influenced many other programming languages, including C++, Java, and Python

A string in C language is a sequence of characters stored in an array.

• Strings in C are represented as arrays of characters.

• They are terminated by a null character '\0'.

• Strings can be manipulated using various string functions like strcpy, strcat, etc.

C language is a programming language used for system programming and data is information processed or stored by a computer.

• C language is a general-purpose programming language known for its efficiency and low-level programming capabilities.

• Data refers to information that is processed or stored by a computer, such as numbers, text, images, etc.

• C language allows programmers to manipulate and work with data using variables, data types, and functions.

• Example: In C language, you c...read more

printf() is used to print formatted output to the console, while scanf() is used to read formatted input from the console.

• printf() is used to display output on the console, allowing for formatting options like specifying the number of decimal places or padding with leading zeros.

• scanf() is used to read input from the console, allowing for formatting options like reading integers, floats, or strings.

• Both functions are part of the standard input/output library in C and are comm...read more

Swapping two numbers without using pointers

• Use arithmetic operations to swap the values

• Use XOR operator to swap the values

• Use temporary variable to swap the values

Keyword Extern is used to declare a variable or function that is defined in another file.

• Extern keyword is used to tell the compiler that the variable or function is defined in another file.

• It is commonly used in header files to declare variables or functions that are defined in source files.

• Extern keyword is not used when defining the variable or function, only when declaring it.

• Example: extern int x; // declares variable x that is defined in another file

• Example: extern void...read more

Arrays are a collection of elements of the same data type, while pointers are variables that store memory addresses.

• Arrays are accessed using indices, while pointers are accessed using dereferencing.

• Arrays have a fixed size, while pointers can be dynamically allocated.

• Arrays can be directly assigned values, while pointers need to be assigned memory addresses.

• Arrays can be passed as arguments to functions, while pointers can be used to modify values in functions.

Program to print 'Hello, World!' in C language

• Include stdio.h header file

• Use printf() function to print 'Hello, World!'

• Return 0 at the end of the program

C is a procedural programming language known for its efficiency and low-level control over hardware.

• C is a general-purpose language used for system programming, embedded systems, and application development.

• It is a compiled language that allows direct memory manipulation and low-level access to hardware.

• C is known for its simplicity, portability, and efficiency.

• Examples of C-based software include operating systems like Unix, programming languages like Python, and game engine...read more

Storage classes define the scope and lifetime of variables in C programming language.

• There are four storage classes in C: auto, register, static, and extern.

• Auto variables are local to a block and have automatic storage duration.

• Register variables are stored in CPU registers for faster access.

• Static variables have a lifetime throughout the program and are initialized only once.

• Extern variables are declared outside of any function and can be accessed by any function in the pro...read more

Storage classes in C define the scope and lifetime of variables.

• C has four storage classes: auto, register, static, and extern.

• Auto variables are local to a block and have automatic storage duration.

• Register variables are stored in CPU registers for faster access.

• Static variables have a lifetime throughout the program and are initialized only once.

• Extern variables are declared in one file and can be accessed in other files.

• Memory layout of C includes stack, heap, and data seg...read more

Yes, I like C programming language.

• I find C to be a powerful and efficient language for low-level programming.

• It has a rich library of functions and is widely used in operating systems and embedded systems.

• C is also a great language for learning computer science fundamentals.

• For example, I have used C to implement data structures like linked lists and binary trees.

Static memory allocation is done at compile-time, while dynamic memory allocation is done at runtime.

• Static memory allocation is used for variables that are fixed in size and do not change during program execution.

• Dynamic memory allocation is used for variables that can change in size during program execution.

• Static memory allocation is faster than dynamic memory allocation.

• Dynamic memory allocation is useful when the size of the data is not known at compile-time.

• Examples of ...read more

Offset is the distance between a reference point and the actual point of interest, resulting in a deviation from the intended position.

• Offset is the difference between the desired position and the actual position of an object or component.

• It can be positive or negative, indicating whether the actual position is to the right or left, above or below, etc.

• In aerospace design, offset can affect the aerodynamics, stability, and overall performance of an aircraft or spacecraft.

• For ...read more

A C program to swap two numbers

• Declare two variables to store the numbers

• Take input for the two numbers

• Swap the values using a temporary variable

• Print the swapped values

C code to find the sum of elements in an array

• Declare an array of integers

• Initialize the array with values

• Use a loop to iterate through the array and add each element to a variable

• Print the sum of the elements

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

• Structures are used to represent real-world entities or concepts in programming.

• They can contain variables of different data types, including other structures.

• Structures provide a way to organize related data and improve code readability and maintainability.

• You can access the members of a structure using the dot (.) operator.

• Structures can be passed as func...read more

C language is used in test due to its efficiency and low-level control over hardware.

• C is a low-level language that allows for direct manipulation of hardware

• C is efficient in terms of memory usage and execution speed

• C is widely used in embedded systems and operating systems

• C allows for easy integration with assembly language

• Examples of C-based tests include system-level testing and hardware testing

Call by value passes a copy of the actual parameter, while call by reference passes the address of the actual parameter.

• Call by value: actual parameter values are copied into formal parameters. Changes made to formal parameters do not affect actual parameters.

• Call by reference: actual parameter addresses are passed into formal parameters. Changes made to formal parameters affect actual parameters.

• Example: Call by value - int a = 5; func(a); // a remains 5. Call by reference -...read more

A function in C is declared by specifying the return type, function name, and parameters (if any).

• The return type specifies the type of value the function will return.

• The function name is used to call the function.

• Parameters are optional and specify the input values the function expects.

• Function declaration ends with a semicolon.

Toggle the fourth bit of a given number.

• Extract the fourth bit using bitwise AND operation with 8 (1000 in binary)

• Toggle the fourth bit using bitwise XOR operation with 8 (1000 in binary)

The c language band which function is used is stdio.h

• The stdio.h library provides input/output functions for C programs

• Functions like printf(), scanf(), fopen(), fclose(), etc. are included in stdio.h

• The band which function is used is determined by the specific function being called

The reverse of malloc() function is free().

• The malloc() function is used to allocate memory dynamically.

• The free() function is used to deallocate the memory allocated by malloc().

• Freeing memory is important to prevent memory leaks and optimize memory usage.