The C programming language is the base for all programming languages. C is one of the oldest and still most used programming languages. It is simple to understand and it supports fast compilation. C was developed to create UNIX operating systems. Today, the UNIX operating system is the most used network operating system all over the world.<\/p>\n
In this tutorial, we showed some important and trending interview questions of the C programming language. These questions are based on different types of concepts in C. It will help you in getting placed at big companies such as TCS, Infosys, Wipro, Accenture etc.<\/p>\n
These interview questions will help you to understand the basic concepts of the C programming language.<\/p>\n
Q.1 State the difference between typedef and #define.<\/strong><\/p>\n Ans.<\/strong> With the help of typedef keyword<\/strong>, you can give alternative names to the existing data type. With this, you cannot create a new data type. It is mainly used in structures, unions etc. to reduce the complexity of the program code.<\/p>\n Syntax of typedef:-<\/strong><\/p>\n Example:-<\/strong><\/p>\n #define<\/strong> is a preprocessor directive. The main purpose of this is to replace the value before compilation. It gives an alias name for the defined macro.<\/p>\n Syntax of #define:-<\/strong><\/p>\n Example:-<\/strong><\/p>\n Q.2 Tell the difference between long and double data types.<\/strong><\/p>\n Ans.<\/strong> These both data types have similar purposes but they are different. For storing large integer values, you can use the long data type. And for storing floating point values which have higher precision than float, you can use a double data type.<\/p>\n long data type<\/strong> Syntax of long:-<\/strong><\/p>\n double data type<\/strong><\/p>\n The main purpose of this is to store decimal numbers with double precision. Syntax of double:-<\/strong><\/p>\n Q.3 Why should you use macros over functions?<\/strong><\/p>\n Ans.<\/strong> One big advantage of using macros over functions is that macros are preprocessed. Unlike functions, Macros are processed before the compilation of a program. Functions are not preprocessed. They are simply compiled.<\/p>\n Macros in C<\/strong><\/p>\n You can say that macro is a piece of code that is replaced by the value of the macro throughout the program. You can define a macro with #define<\/strong> directive. At the end of defining a macro, you don\u2019t have to put a semicolon(;) to terminate it.<\/p>\n Example:-<\/strong><\/p>\n Output:-<\/strong> Functions in C<\/strong><\/p>\n Functions are very useful for all the programming languages. With the help of functions, you can divide a large block of code into small blocks of code and you can also execute those blocks of code again and again. It will save your precious time.<\/p>\n E<\/strong>xample:-<\/strong><\/p>\n Q.4 What is the output of the following program?<\/strong><\/p>\n Ans.<\/strong> 15<\/p>\n Q.5 Can you give arguments to the main() function?<\/strong><\/p>\n Ans.<\/strong> Yes, you can give command line arguments to the main function. You can only pass two arguments to the main function which are argc<\/strong> and argv.<\/strong><\/p>\n Example:-<\/strong><\/p>\n If you give an argument such as \u201cHave a nice day\u201d from the terminal then it will print you the below output.<\/p>\n Output:-<\/strong> Q.6 What is the Difference between local and global variables in C.<\/strong><\/p>\n Ans.<\/strong><\/p>\n Q.7 Why C is known as the base for all programming languages?<\/strong><\/p>\n Ans.<\/strong> Using the C programming language, several compilers and JVM\u2019s are written. Many programming languages have borrowed the syntax and semantics of C like Python, Java, Rust etc. The C programming language gave birth to new concepts such as array, file handling, pointers, functions etc which are used by these languages also.<\/p>\n Q.8<\/strong> What is the use of printf() and scanf() functions in C?<\/p>\n Ans.<\/strong> The main purpose of this function is to display the output on the screen. With the help of the scanf()<\/strong> function, you can take input from the user.<\/p>\n Q.9<\/strong> Why to use static variables in C? Q.10<\/strong> Why to use functions in C? Q.11<\/strong> What is the output of the following program?<\/p>\n Ans.<\/strong> 09<\/p>\n Q.12<\/strong> What is dynamic memory allocation? Example:-<\/strong><\/p>\n Q.13<\/strong> Can you compile a program without the main() function?<\/p>\n Ans.<\/strong> Yes, you can compile a program without the main() function but that program cannot be executed. If you want to run and compile a program without the main() function then you can make use of #define.<\/strong><\/p>\n Example:-<\/strong><\/p>\n Q.14<\/strong> What is the output of the following program?<\/p>\n Ans.<\/strong> This program won\u2019t throw you an error. But the fun() function won\u2019t get executed. So, the program will print nothing.<\/p>\n Syntax:-<\/strong><\/p>\n Q.15<\/strong> Write a program to check if the number is an Armstrong number or not.<\/p>\n Ans.<\/strong><\/p>\n Output:-<\/strong> Q.16<\/strong> Write a program to reverse a number in C?<\/p>\n Ans.<\/strong><\/p>\n Output:-<\/strong> Q.17<\/strong> What is the output of the following program?<\/p>\n Ans.<\/strong> 5<\/p>\n Q.18<\/strong> Why should you use the sprintf() function in C?<\/p>\n Ans.<\/strong> The sprintf() function stands for string print. You cannot display the output on the screen using this function. It helps you to transfer the data into the buffer.<\/p>\n Syntax:-<\/strong><\/p>\n Example:-<\/strong><\/p>\n Q.19<\/strong> Why does n + + execute faster than the n+1?<\/p>\n Ans.<\/strong> n++ needs only one variable. It is a unary operator. n+1 is a binary operation that adds overhead to take more time. In modern compilers, the execution of time of both n++ and n+1 are equivalent.<\/p>\n Example:-<\/strong><\/p>\n Output:-<\/strong> Q.20<\/strong> Why does the C programming language not support function overloading?<\/p>\n Ans.<\/strong> The C programming language does not support strict typing. In C, many things are implicitly convertible to each other. In C, if you introduce function overloading then you should provide a name mangling technique to prevent the name clashes. When you compile a C program code, the symbol names will remain intact.<\/p>\n Q.21<\/strong> Can you point out the error in the following code?<\/p>\n Ans.<\/strong> The above program will give you an error because you will not get input for the second scanf() statement.<\/p>\n Q.22<\/strong> Why to use the new and delete operators in C?<\/p>\n Ans.<\/strong> The new<\/strong> operator is mainly used for allocating memory. With the help of this operator, you can return a pointer to the beginning of the new block of the allocated memory.<\/p>\n Example:-<\/strong><\/p>\n The delete<\/strong> operator is mainly used for deallocating memory. With the help of this operator, you can free the memory so that it will be available for other purposes.<\/p>\n Example:-<\/strong><\/p>\n Q.23<\/strong> State the difference between call by value and call by reference.<\/p>\n Ans.<\/strong><\/p>\n Example:- call by value<\/strong><\/p>\n Output:-<\/strong> Example:- call by reference<\/strong><\/p>\n Output:-<\/strong> Q.24<\/strong> What is the output of the following program code?<\/p>\n Ans.<\/strong> 120<\/p>\n Q.25<\/strong> Suppose, you created a file named Tech.txt. Then what will be the name of that file after executing the below program?<\/p>\n Ans.<\/strong> Advance<\/p>\n Q.26<\/strong> What is the difference between getch() and getche()?<\/p>\ntypedef data_type name_of_new_data_type;\n<\/pre>\n
typedef unsigned int new_int;\n<\/pre>\n
#define NAME value\n<\/pre>\n
#define SIZE 7\n<\/pre>\n
\nSuppose, a programmer wants to use large numbers on their code then they can use the type specifier named long.<\/strong><\/p>\nlong j; \/\/ for storing integer values\nlong long o; \/\/ for storing integer values\nlong double p; \/\/ for storing floating point values\n<\/pre>\n
\nThe difference between float<\/strong> and double<\/strong> is that the size of float<\/strong> is 4 bytes and the size of double<\/strong> is 8 bytes.<\/p>\ndouble a;\n<\/pre>\n
#include <stdio.h>\n#define SIDE 4\nint main() {\n int area;\n area = SIDE*SIDE;\n printf(\"Area is: %d\",area);\n return 0;\n}\n<\/pre>\n
\nArea is: 16<\/p>\nint sum(int n1, int n2){\nint final;\nfinal = n1 + n2;\nreturn final;\n}\n<\/pre>\n#include <stdio.h>\nint main(void)\n{\nint data;\nint val= 1;\nint arr[4] = { 2, 3, 1, 4};\ndata = 4 * 4 + arr[val++] - (9 \/ val);\nprintf(\"%d\", data);\nreturn 0;\n}\n<\/pre>\n#include <stdio.h>\n\nint main(int argc, char *argv[])\n{\nfor(int i=1; i<argc; i++)\nprintf(\"%s \", argv[i]);\nprintf(\"\\n\");\nreturn 0;\n}\n<\/pre>\n
\nHave a nice day<\/p>\n\n\n
\n Local Variable in C<\/b><\/td>\n Global Variable in C<\/b><\/td>\n<\/tr>\n \n Local variables are declared inside the main function.<\/span><\/td>\n Global variables are declared outside the main function.\u00a0<\/span><\/td>\n<\/tr>\n \n Declared only for the main function.<\/span><\/td>\n Declared for the entire code.<\/span><\/td>\n<\/tr>\n \n These are stored in a stack unless specified.<\/span><\/td>\n For global variables, the compiler decides the storage location.<\/span><\/td>\n<\/tr>\n \n Only be accessible from inside of the main function.<\/span><\/td>\n Only accessible from inside and from outside of the main function.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nBelow are the format specifiers which you can use in the printf() function.<\/p>\n\n
\nAns.<\/strong><\/p>\n\n
\nAns.<\/strong><\/p>\n\n
#include <stdio.h>\nint main()\n{\nint x, y = 3;\nfunc(&x,&y);\nprintf(\"%d%d\",x,y);\nreturn 0;\n}\nvoid func(int *x , int*y)\n{\n*x = *x * *y;\n*y = *y * *y;\n}\n<\/pre>\n
\nAns.<\/strong><\/p>\n\n
int *point= malloc(sizeof(int)*5); \n\n<\/pre>\n
#include<stdio.h> \n#define start main \nvoid start() { \n printf(\"Have a nice day!\"); \n} \n<\/pre>\n#include \"stdio.h\"\nint fun(int num)\n{\nprintf(\"%d\",num);\nreturn 0;\n}\nint main()\n{\nfun;\nreturn 0;\n}\n<\/pre>\n(type_name) expression; \n<\/pre>\n
#include<stdio.h> \t \n#include<conio.h> \t \nint main() \t \n{ \t \nint num=155,rev,sum=0,tmp;\ntmp=num; \t \nwhile(num>0) \t \n{ \t \nrev=num%10; \t \nsum=sum+(rev*rev*rev); \t \nnum=num\/10; \t \n} \t \nif(tmp==sum) \t \nprintf(\"It is an armstrong number!\"); \t \nelse \t \nprintf(\"It is not an armstrong number!\"); \t \ngetch(); \n}\n<\/pre>\n
\nIt is not an armstrong number!<\/p>\nIntermediate C Programming Interview Questions<\/h3>\n
#include<stdio.h> \nint main() \n{ \nint number=265, rev=0, remainer; \nwhile(number!=0) \n{ \nremainer=number%10; \nrev=rev*10+remainer; \nnumber\/=10; \n} \nprintf(\"%d\",rev); \nreturn 0; \n}\n<\/pre>\n
\n562<\/p>\n#include<stdio.h>\n#include<stdlib.h>\nint main()\n{\nint x=25,y=65,res;\nint i;\nfor(i = 1; i <= x && i <= y; i++)\n{\nif((x % i == 0) && (y % i == 0))\n{\nres = i;\n}\n}\nprintf(\"%d\",res);\nreturn 0;\n}\n<\/pre>\nint sprintf ( char *string, const char *name, ... ); \n<\/pre>\n
#include<stdio.h> \nint main() \n{ \nchar string[20]; \nint s1=sprintf(string,\"TechVidvan\"); \nprintf(\"Value of s1: %d\",s1); \nreturn 0;\n}\n<\/pre>\n#include<stdio.h>\n#include<stdlib.h>\nint main()\n{\nint x=2;\nprintf(\"%d\\n\", x++);\nprintf(\"%d\",++x);\nreturn 0;\n}\n<\/pre>\n
\n2
\n4<\/p>\n#include<stdio.h>\n\nint main()\n{\n char c;\n int x;\n scanf(\"%c\", &c);\n scanf(\"%d\", &x);\n printf(\"%c %d\", c, x);\n return 0;\n}\n<\/pre>\nint *ptr;\nptr = new int[20];\n<\/pre>\n
delete ptr;\n<\/pre>\n
\n\n
\n Call by Value<\/b><\/td>\n Call by Reference<\/b><\/td>\n<\/tr>\n \n In this method, the actual values are passed to the function calls.<\/span><\/td>\n In this method, instead of the actual values, the address of the corresponding values are passed to the function calls.<\/span><\/td>\n<\/tr>\n \n Actual and Formal parameters are created at different memory locations.<\/span><\/td>\n Actual and Formal parameters are created at the same memory locations.<\/span><\/td>\n<\/tr>\n \n You cannot change the value of the actual parameter.<\/span><\/td>\n You can change the value of the actual parameters by changing the formal parameter.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n #include<stdio.h> \nvoid func(int n) { \nn=n+50; \nprintf(\"%d\\n\", n); \n} \nint main() { \nint a=10; \nfunc(a); \nreturn 0; \n}\t\n<\/pre>\n
\n60<\/p>\n#include<stdio.h> \nvoid func(int *n) { \n(*n) += 10; \nprintf(\"%d\\n\", *n); \n} \t \nint main() { \nint a=10; \nfunc(&a);\nreturn 0; \n}<\/pre>\n
\n20<\/p>\n#include<stdio.h>\nint fac(int);\nint npr(int, int);\nint main()\n{\n\n int num=5, r=4;\n int res;\n res = npr(num, r);\n printf(\"%d\\n\",res);\n return 0;\n}\n\nint npr(int n1, int n2)\n{\n return (fac(n1)\/fac(n1-n2));\n}\nint fac(int number)\n{\n if(number == 1 || number == 0)\n \treturn 1;\n else\n \treturn number*fac(number-1);\n}\n<\/pre>\n#include <stdio.h>\nint main()\n{\nint res;\nchar o[] = \"Tech.txt\";\nchar n[] = \"Advance.txt\";\nres = rename(o, n);\nif (res == 0)\nputs(\"success\");\nelse\nperror(\"Error\");\nreturn 0;\n}\n<\/pre>\nAdvanced C Interview Questions and Answers<\/h3>\n