Elevate Your Programming Skills with Essential C Language Knowledge

Discover the most frequently asked C interview questions with expert answers to help you prepare for technical interviews. This guide covers key C language concepts, essential programming techniques, and the best ways to showcase your C skills in interviews, making it a must-read for both beginners and experienced programmers.

The C language is one of the foundational programming languages in computer science. Known for its simplicity and efficiency, C enables developers to work directly with memory, making it ideal for system-level programming and embedded systems. Understanding C language basics is critical, as it forms the foundation for learning advanced languages and concepts in programming.

1. What is c language?

   1. C language is a computer programming language and in other words c language is procedural language and also called as structural language. Basically c language is a mid level programming to develop assembly level language. C supports both low level and high level feature to develop independent operating system and also application programs.
      
      

2. What are the data types supported by c language?

   1. C language primarily supports three categories of data types

      • Primary/ primitive data types

        • Integer

        • Character

        • Float Pointer

        • Double Float Pointer

        • Void

      • Derived Data types

        • Function

        • Array

        • Pointer

        • Referecne

      • User defied data types

        • Class

        • Structure

        • Union

        • Enum

        • Typedef
          
          Syntax

          dataType variableName = value;

          
          Example:

          #include <stdio.h>
          int main ()
          {
            int num = 5;
            float fnum = 5.99;
            char ch = 'D';
            printf ("%d\n", num);
            printf ("%f\n", fnum);
            printf ("%c\n", ch);
            return 0;
          }

3. What are the features of c language?

   1. It is Simple And Efficient. 
      portable or Machine Independent.
      C supports mid-level Programming.
      It is a structured oriented Programming Language.
      It has a function-rich library.
      Dynamic Memory Management.
      C is super fast.
      We can use pointers in C.
      It is extensible.

4. What is printf() function?

   1. Printf() funntion is used to print the values or text
      Syntax:

      printf("format string",argument_list);

      
      Example:

      printf("Naresh I Technologies");
      like python  or java display the values normally but in c language it is not possible if want to print we use format specifier like %d or %s etc.
      %d: used to print an integer value.
      %s: used to print a string.
      %c: used to display a character value.
      %f: used to display a floating point value

      
      Example:

      int num = 5;
        float fnum = 5.99;
        char ch = 'D';
        printf ("%d\n", num);
        printf ("%f\n", fnum);
        printf ("%c\n", ch);
      printf(num) // not possible 

5. What is scanf() function?

   1. Scanf() function takes the input from user keyboard in other words it reads the input data from the console
      Syntax:

      scanf("format string",argument_list);
      like printf it support formats spcifiers
      %d: used to print an integer value.
      %s: used to print a string.
      %c: used to display a character value.
      %f: used to display a floating point value.

      
      Example:

      scanf("%d",&num);  here  ‘num’ is a integer variable
      Sample program:
      #include<stdio.h>
      int main ()
      {
        int num;
        printf ("enter a number:");
        scanf ("%d", &num);
        printf ("Entered number is:%d ", num);
        return 0;
      }

      You can learn more about it in our Free Demo. 

6. How to declare variables in c language?

   1. Variables are containers for storing data values, like numbers and characters.
      Syntax to declare variable:

      datatype NameOfVarible = value;

      
      Example:

      Int a = 10
      Char ch = ‘A’;

7. What are the difference between malloc() and calloc()?

   1. malloc() and calloc() both are used to create dynamic allocation but we have some difference
      malloc() function that allocates fixed size of one block of memory where as calloc() function assigns more than one block of memory to a single variable.
      malloc() function more faster and when compared to calloc().

8. What is malloc() function?

   1. malloc() is nothing but “memory allocation” which is used to dynamic memory allocation of single block with fixed size. 
      It returns a pointer of type void which can be cast into a pointer of any form.
      It does not initialize memory at the time of execution, so that it has initialized each block with the default garbage value initially.
      malloc() function defined under <stdlib.h> in c
      Syntax:

      ptr = (cast-type*) malloc(byte-size)

      
      Example:

      ptr = (int*) malloc(100 * sizeof(int)); // for interger
      char **file;
      file = (char **)malloc(sizeof(char *) * (size + 1)) // for character
      Sample program:
      #include<stdio.h>
      #include<stdlib.h>
      int main ()
      {
          int* ptr;
          int n = 1;
          if(ptr ==NULL)
          {
              printf ("First Memory not allocated\n");
          }
          else
          {
              printf ("First Memory allocated\n");
          }
          ptr = (int*)malloc(n * sizeof(int));
          if (ptr == NULL) {
              printf("Second Memory not allocated.\n");
              exit(0);
          }
          else
          {
              printf ("Second Memory allocated");
          }
        return 0;
      }

      Take the C Fundamentals skill track to gain the foundational skills you need to become a programmer. 

9. What is calloc() function?

   1. calloc() function is also known as “contiguous allocation” used to allocate dynamic memory the specified number of blocks of memory of the specified type.
      It initializes each block with a default value ‘0’.
      calloc() function defined under <stdlib.h> in c
      Syntax:

      ptr = (cast-type*)calloc(n, element-size);

      
      Example:

      ptr = (float*) calloc(16, sizeof(float));
      Sample program:
      #include<stdio.h>
      #include<stdlib.h>
      int main ()
      {
          int* ptr;
          if(ptr ==NULL)
          {
              printf ("First Memory not allocated\n");
          }
          else
          {
              printf ("First Memory allocated\n");
          }
         
          ptr = (int*)calloc(10, sizeof(int)); // calloc Memory allocation
          if (ptr == NULL) {
              printf("Second Memory not allocated.\n");
              exit(0);
          }
          else
          {
              printf ("Second Memory allocated");
          }
        return 0;
      }

10. What is free() function?

    1. In c, free() function is used for de-allocation of memory is allocated by malloc() and calloc() functions and both are not deallocated by itself. By using free() function to reduce wastage of memory by freeing it.
       Syntax:

       free(ptr);

       
       Sample program:

       #include<stdio.h>
       #include<stdlib.h>
       int main ()
       {
           int *mpointer, *cpointer;
           mpointer = (int*)malloc(10 *sizeof(int)); // malloc Memory allocation
           cpointer = (int*)calloc(10, sizeof(int)); // calloc Memory allocation
           if(mpointer ==NULL || cpointer==NULL)
           {
               printf ("First Memory not allocated\n");
           }
           else
           {
               printf("Malloc Memory allocated \n");
               free(mpointer); // free malloc memory
              
               printf("Calloc Memory allocated \n");
               free(cpointer);
               if(mpointer==NULL && cpointer==NULL)
               {
                   printf("deallocatoin completed\n");
               }
               else
               {
                   printf("deallocatoin not completed\n");
               }
           }
         return 0;
       }

       Take the essential practicing coding interview questions course to prepare for your next coding interviews

11. What is realloc() function?

    1. In C, realloc() is also called as re-allocation of memory. If the memory previously allocated with the help of malloc or calloc is insufficient, realloc can be used to dynamically re-allocate memory.
       Syntax

       ptr = realloc(ptr, newSize);

       
       Sample Program:

       #include<stdio.h>
       #include<stdlib.h>
       int main ()
       {
           int *pointer;
           pointer = (int*)malloc(6 *sizeof(int)); // malloc Memory allocation
           if(pointer==NULL)
           {
               printf ("Memory not allocated\n");
           }
           else
           {
               printf("Memory allocated\n");
               printf("Size of Pointer %ld \n",malloc(sizeof(pointer)));
               pointer = (int*)realloc(pointer, 26 * sizeof(int));
               printf("Size of Pointer %ld \n",malloc(sizeof(pointer)));
           }
          
         return 0;
       }

12. What is atio() frunction?

    1. The atoi() function converts an integer value from a string of characters. It returns numaric value.
       The function stops reading the input string when it encounters the first character that it does not consider part of a number. It may be the null character at the string ends.
       The atoi() function doesn't support the exponents and decimal numbers.
       The atoi() function skips all the white space characters at the starting of the string. It also converts the characters as the number part and stops when it finds the first non-number character.
       atoi() function defined under <stdlib.h> in c
       Syntax:

       int atoi(const char *str)
       Sample Program:
       #include<stdio.h>
       #include<stdlib.h>
       int main ()
       {
           int val;
           char first[] = "212541";
           char second[] = "NareshIT";
           char third[] = "1234NareshIT123";
          
           val = atoi(first);
           printf("result of first variable %d \n",val);
           val = atoi(second);
           printf("result of second variable %d \n",val);
           val = atoi(third);
           printf("result of third variable %d \n",val);
          
         return 0;
       }

13. How abs() function works in c language?

    1. The abs () function is a predefined function in the stdlib.h header file to return the absolute value i.e. positive of the given integers.
       Syntax:

       int abs(int a);

       
       Sample program:

       #include<stdio.h>
       #include<stdlib.h>
       int main ()
       {
          
           printf("abs of -25 is %d \n",abs(-25));
           printf("abs of 25 is %d \n",abs(25));
          
         return 0;
       }

14. What is sprintf()?

    1. In c language sprint() function stands for “String Print” converts any data variable into string value. Instead of printing on console, sprintf() function stores the output on char buffer that is specified in sprint.
       Syntax:

       int sprintf(char *str, const char *string,...);

       
       Example:

       #include <stdio.h>
       int main()
       {
           char ch[50];
           int a = 22, b = 26, c;
           c = a + b;
           float f = 15.1;
           sprintf(ch, "Sum of %d and %d is %d\n", a, b, c);
           printf("%s", ch);
           sprintf(ch, "%f", f);
           printf("%s", ch);
           return 0;
       }

15. What is the difference between puts and gets function in c language?

    1. Puts() function to prints output and gets() function involves takes input from user.

       #include <stdio.h>
       int main()
       {
           char ch[50];
           gets(ch);
           puts(ch);
       
           return 0;
       }

Elevating Your Programming Skills

Mastering the C language is a powerful way to elevate your programming skills. It lays the foundation for understanding essential programming concepts, including memory management, pointers, and data structures. These skills are highly sought after in technical interviews and can also ease your journey into more advanced languages.

To maximize your learning, consider C Language Online Training with expert guidance, hands-on exercises, and real-world applications. With structured online training, you'll gain a deep, practical understanding of C that will help you confidently tackle complex programming challenges and achieve your career goals.

Final Thoughts:

Whether you're preparing for a technical interview or looking to strengthen your programming foundation, learning C is an invaluable step. C provides insight into how computers work at a low level and builds a solid base for learning other languages. By mastering C interview questions, you’ll boost your confidence and readiness to excel in any technical discussion.