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Q1. You know what are Increment and Decrement operators correct? What I want to know is how increment and decrement operators can be constructed using basic mathematical operators?<\/strong><\/p>\n\n\n Ans. (First, in a line explain Increment and Decrement operators then answer the question<\/em>)<\/p>\n\n\n Increment and Decrement operators are used to increase or decrease the value of the variable by 1. We can achieve this functionality by using ‘+’ and ‘-‘ operators. For eg:<\/p>\n\n\n (Such example will show your understanding of post and pre, increment\/decrement also<\/em>)<\/p>\n\n\n Q2. How will you print \u201cHello World\u201d without using semicolon even once in your code?<\/strong><\/p>\n\n\n Ans. (Simply write the below code and explain it\u2019s working<\/em>)<\/p>\n\n\n printf() function will print \u201cHello World\u201d to the console. It will return a non-zero value to if<\/em> statement and there is no other code to execute.<\/p>\n\n\n (Interesting fact<\/em>: printf returns the number of characters(including space) inside the inverted quotes according to data structures using c. For the above example, it will return 11.)<\/p>\n\n\n Q3.<\/strong> Do you know how many places a variable can be declared in C? If you do, then mention the places and the type of variable corresponding to that place.<\/strong><\/p>\n\n\n Ans. (Name all the 3 places where the variables can be declared<\/em>)<\/p>\n\n\n Variables can be declared in 3 places:<\/p>\n\n\n These positions correspond to<\/p>\n\n\n Q4. Explain Local variables, Formal parameters and Global variables.<\/strong><\/p>\n\n\n Ans. Local Variables:<\/p>\n\n\n (Interesting fact<\/em>: A variable declared within one block has no relationship to another variable with the same name declared within a different code block.)<\/p>\n\n\n Formal Parameters:<\/p>\n\n\n Global Variables:<\/p>\n\n\n (Interesting fact<\/em>: After defining a local variable, the system or the compiler won’t be initializing any value to it.<\/p>\n\n\n Global variables get initialized automatically by the compiler as and when defined based on datatype. int = 0, char = ”, float = 0, double = 0 and pointer = Null)<\/p>\n\n\n Q5. Explain to me the concept of Null pointer. And if you can, shed some light on Dangling pointer as well.<\/strong><\/p>\n\n\n Ans. If the pointer variable is not assigned any valid memory address then NULL can be used to initialize that pointer. (Conceptually, the NULL pointer doesn’t point anywhere)<\/p>\n\n\n (Interesting fact<\/em>: we have a void pointer as well. A pointer that points to some data location in storage, which doesn’t have any specific type, so “void” pointer).<\/p>\n\n\n Dangling pointer: Pointer that doesn’t point to a valid memory location. (Don’t stop here it will give the interviewer a chance to confuse you, provide a detailed answer<\/em>)<\/p>\n\n\n If you delete or deallocate a memory of an object without modifying the pointer pointing to it, in such cases dangling pointer arises.<\/p>\n\n\n Q6. In a C language, how many ways are there of passing arguments to a subroutine(function)?<\/strong><\/p>\n\n\n Ans. In C language there are two ways that arguments can be passed to a subroutine.<\/p>\n\n\n (Now explain these two points)<\/p>\n\n\n (You can stop here, or you can also provide a simple Swap function example for Call by Reference<\/em>)<\/p>\n\n\n Q7. Is there a way in C programming such that the local variables maintain their values between function calls?<\/strong><\/p>\n\n\n (Sometimes a question is not asked directly, such as above question could be asked simply as – Explain use of static keyword in C language<\/em>)<\/p>\n\n\n Ans. (First, explain static<\/strong> keyword<\/em>)<\/p>\n\n\n Variables declared as static<\/strong> are permanent variables within their own function or file. They are not known outside their function or file.<\/p>\n\n\n (Now, explain only about static<\/strong> Local Variable, no need to explain about static<\/strong> Global Variables<\/em>)<\/p>\n\n\n static<\/strong> Local Variables: When you apply the static<\/strong> modifier to a local variable, the compiler creates permanent storage for it, much as it creates storage for a global variable.<\/p>\n\n\n The key difference between a static<\/strong> local variable and a global variable is that the stati<\/b><\/span>c local<\/strong> variable remains known only to the block in which it is declared.<\/p>\n\n\n In simple terms, a static<\/strong> local variable is a local variable that retains its value between function calls.<\/p>\n\n\n Q8. <\/strong>You can easily print numbers from 1 to 100 using a loop, can you do the same without using any type of loop?<\/strong><\/p>\n\n\n Ans. (Use recursion instead loop)<\/p>\n\n\n Q9. <\/strong>In the lines <\/strong>#include <stdio.h><\/strong>, <\/strong>#define MOD 10000007<\/strong>, what are #include and #define?<\/strong><\/p>\n\n\n Ans. (Interviewer is expecting an explanation of Preprocessor Directives<\/em>)<\/p>\n\n\n #include and #define are Preprocessor directives. Preprocessor directives are placed at the beginning of every C program. This is where library files are specified, another use is to declare constants. Preprocessors are programs that process our source code before compilation.<\/p>\n\n\n #include<\/strong> – It is used to include libraries, which would depend on what functions are to be used in the program.<\/p>\n\n\n #define<\/strong> – It defines an identifier and a character sequence that will be substituted for the identifier each time it is encountered in the source file. The identifier is referred to as a macro name<\/em> and the replacement process as a macro replacement<\/em>.<\/p>\n\n\n (Interesting fact<\/em>: Each preprocessing directive must be on its own line. For example, this will not work -> #include <stdio.h> #include<stdlib.h> )<\/p>\n\n\n Q10. Explain about Entry control and Exit control loops in C.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q11. Memory layout of C consist of Text, Data, Stack and Heap areas, explain about stack and heap areas?<\/strong><\/p>\n\n\n Ans. Stack Area: It is used to store local variables and is used for passing arguments<\/strong> to the functions along with the return address of the instruction which is to be executed after the function call is over. These values stay in the memory only till the termination of that function.<\/p>\n\n\n Heap Area: Heap is a segment where dynamic memory allocation usually takes place. In C language dynamic memory allocation is done by using malloc() and calloc() functions.<\/p>\n\n\n Q12. In which memory segment of the C program, static variables are stored?<\/strong><\/p>\n\n\n Ans. (There are two cases here, explain both to the interviewer)<\/p>\n\n\n Q13. What functions are used for dynamic memory allocation in C language?<\/strong><\/p>\n\n\n Ans. Standard C defines four dynamic allocation functions that all compilers will supply:<\/p>\n\n\n Q14. Can we convert a higher data type into a lower data type in C? If yes, then how?<\/strong><\/p>\n\n\n Ans. (Typecasting is asked here)<\/p>\n\n\n Yes, we can convert higher data type into lower data type using explicit typecasting. Typecasting<\/strong> is a way to convert a variable from one data type to another data type.<\/p>\n\n\n But it is not a good practice to convert the higher data type to lower data type, because data will be truncated when the higher data type is converted into a lower data type, resulting in data loss.<\/p>\n\n\n If a float is converted to int, then we will lose values after decimal point (5.550 -> 5, a loss of .550).<\/p>\n\n\n Q15. Explain all the types of recursion.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q16. Write a program to swap two numbers without using the third variable?<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q17. Write a program to find the Fibonacci series without using recursion?<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q18. Write a program to print Fibonacci series using recursion?<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q19. Write a C program to check whether a number is Prime or not.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q20. Write a program to check whether the number is prime or not using recursion.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q21. Write a program to check whether a number is Palindrome number or not in C programming.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q22. Write a program to print factorial (without recursion) in C programming.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q23. Write a program to print factorial (using recursion) in C programming.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q24. Write a C program to check whether a number is Armstrong or not.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q25. Write a C program to reverse an Integer.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q26. Write a C program to find the sum of two integers without using ‘+’ operator.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q27. Write a C program to print \u201cHello World\u201d with the double-quotes.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q28. Write a C program to divide an integer by 2 without using \u2018\/\u2019 operator.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n (Interesting fact: Right shift operator is used to divide a number by powers of 2. N>>1 == N\/2, N>>2 == N\/4, N>>3 == N\/8. Same is the case with Left shift operator, it is used for multiplication.)<\/em><\/p>\n\n\n Q29. Write a C program to reverse a String in C with the help of recursion.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q30. Can the size of an array be declared at runtime in C?<\/strong><\/p>\n\n\n Ans. No, in array declaration, the size must be known at compile time. You can\u2019t specify a size that\u2019s known only at runtime. The compiler needs to store memory for the array, and to do that compiler requires Array\u2019s size at compile.<\/p>\n\n\n For example:<\/p>\n\n\n Q31. Write a C program to convert String into Integer without using library function.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q32. Write a C program to convert an integer into a string without using library function.<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q33. What is the difference between Macros and Functions?<\/strong><\/p>\n\n\n Ans.<\/p>\n\n\n Q34. How will you find the total number of elements in the array if the size of the array is not provided?<\/strong><\/p>\n\n\n\n int x=1;\n int y= x++; \/\/ this can be divided into two steps (y=x; x=x+1;)\n int z= --x; \/\/ this can be divided into two steps (x=x+1; z=x;)\n <\/code><\/pre>\n\n\n int main(void)\n {\n if(printf(\u201cHello World\u201d))\n {\n }\n }\n\n<\/pre>\n\n\n\n int* dang = (int *)malloc(sizeof(int));\n free(dang); \/\/ deallocated the memory used by the dang variable.\n *dang = 100; \/\/ now the pointer is pointing to invalid memory locations. So, this becomes a dangling pointer.\n <\/code><\/pre>\n\n\n\n #include<stdio.h>\n void swap(int *x, int *y)\n {\n int temp;\n temp=*x;\u00a0 \/\/ store the value present at address of \u2018x\u2019\n *x=*y;\u00a0\u00a0\u00a0 \/\/ copy the value present at the address of \u2018y\u2019 to address of \u2018x\n *y=temp;\u00a0 \/\/ copy the value present in temp to address of \u2018y\u2019\n }\n int main(void)\n {\n int i=10, j=20;\n swap(&i, &j);\n printf(\"i=%d and j=%d\",i,j);\n return 0;\n }\n<\/code><\/pre>\n\n\n
\n #include <stdio.h>\n int product();\n int main()\n {\n product();\n return 0;\n }\n int product()\n {\n static int var = 1; \/\/ var initialized to 1\n var=var*5; \/\/ updates value of var, this will be retained after recursive call as well\n if(var>1000)\n return;\n printf(\"%d, \", var);\n product();\n }\n<\/code>\n<\/pre>\n\n\n\n #include<stdio.h>\n void printNumbers(int);\n int main()\n {\n int n=1;\n printNumbers(n);\n return 0;\n }\n void printNumbers(int n)\n {\n if(n<=100)\n {\n printf(\"%d \", n);\n printNumbers(n+1);\n }\n }\n<\/code><\/pre>\n\n\n#include<stdio.h>\nint main()\n{\n int x=50, y=60;\n x=x+y; \/\/ x=110 (50+60)\n y=x-y; \/\/ y=110-60 =50\n x=x-y; \/\/ x=110-50 =60\n \/\/ so now x=60 and y=50.\n printf(\u201cx=%d and y=%d\u201d,x,y);\n return 0;\n}\n<\/code><\/pre>\n\n\n\n #include<stdio.h>\n void main()\n {\n int num1=0,num2=1,num3,i,number;\n printf(\"Enter the number of elements: \");\n scanf(\"%d\",&number);\n printf(\"%d %d\",num1,num2);\n for(i=2;i<number;i++)\n {\n num3=num1+num2;\n printf(\" %d\",num3);\n num1=num2;\n num2=num3;\n }\n }\n<\/code><\/pre>\n\n\n\n #include<stdio.h>\n int fib(int);\n int main()\n {\n int num=0,i,n;\n scanf(\"%d\",&n);\n printf(\"Fibonacci series: \n\");\n for(i=1;i<=n;i++)\n {\n printf(\"%d \",fib(num));\n num++;\n }\n }\n int fib(int n);\n {\n if(n==0 || n==1)\n return n;\n else\n return (fib(n-1))+fib(n-2)); \n }\n<\/code><\/pre>\n\n\n\n #include<stdio.h>\n #include<math.h>\n int main()\n {\n int num,i;\n int flag=0;\n printf(\"Enter any positive number: \n\");\n scanf(\"%d\",&num);\n for(i=2;i<=sqrt(num);i++)\n {\n if(num%i==0)\n {\n flag=1;\n break;\n }\n }\n if(flag==0)\n {\n printf(\"%d is Prime Number\",num);\n }\n else\n {\n printf(\"%d is not a Prime Number\",num);\n }\n return 0;\n }\n<\/code><\/pre>\n\n\n #include<stdio.h>\n int isPrime(int,int);\n int main()\n {\n int n,i=2;\n printf(\"Enter any positive number: \n\");\n scanf(\"%d\",&n);\n if(isPrime(n,i)==1)\n {\n printf(\"Yes\");\n }\n else\n {\n printf(\"No\");\n }\n }\n int isPrime(int n, int i)\n {\n if(n<2)\n return 0;\n if(n==2)\n return 1;\n if(n%i==0)\n return 0;\n if(i*i > n)\n return 1;\n return isPrime(n,i+1);\n }\n\n<\/pre>\n\n\n #include<stdio.h>\n int main()\n {\n int num,rem,sum=0,temp;\n printf(\"enter the number=\");\n scanf(\"%d\",&num);\n temp=num;\n while(num>0)\n { \n rem=num%10;\n sum=(sum*10)+rem;\n num=num\/10;\n }\n if(temp==sum)\n printf(\"Palindrome number \");\n else\n printf(\"Not palindrome\");\n return 0;\n }\n\n<\/pre>\n\n\n #include<stdio.h>\n int main()\n {\n int i,fact=1,num;\n printf(\"Enter a number: \");\n scanf(\" %d \",&numb);\n for(i=1;i<=numb;i++)\n {\n fact=fact*i;\n }\n printf(\"Factorial of %d is: %d\",num,fact);\n return 0;\n }\n\n<\/pre>\n\n\n\n #include <stdio.h>\n long int factorial(int n);\n int main()\n {\n int n;\n printf(\"Enter a positive integer: \");\n scanf(\"%d\", &n);\n printf(\"Factorial of %d = %ld\", n, factorial(n));\n return 0;\n }\n long int factorial(int n)\n {\n if (n >= 1)\n return n*factorial(n-1);\n else\n return 1;\n }\n<\/code><\/pre>\n\n\n\n #include <stdio.h>\n #include <math.h>\n int main()\n {\n int number, tempNum, rem, result = 0, n = 0 ;\n printf(\"Enter an integer: \");\n scanf(\"%d\", &number);\n tempNum = number;\n while (tempNum != 0)\n {\n tempNum \/= 10;\n ++n;\n }\n tempNum = number;\n while (tempNum != 0)\n {\n rem = tempNum%10;\n result += pow(rem, n);\n tempNum \/= 10;\n }\n if(result == number)\n printf(\"%d is an Armstrong number.\", number);\n else\n printf(\"%d is not an Armstrong number.\", number);\n return 0;\n }\n<\/code><\/pre>\n\n\n\n #include <stdio.h>\n int main()\n {\n int n, reverseNum = 0, rem;\n printf(\"Enter an integer: \");\n scanf(\"%d\", &n);\n while(n != 0)\n {\n rem = n%10;\n reverseNum = reverseNum*10 + rem;\n n \/= 10;\n }\n printf(\"Reversed Number = %d\", reverseNum);\n return 0;\n }\n<\/code><\/pre>\n\n\n\n #include<stdio.h>\n int main()\n {\n int x=10;\n int y=20;\n int sum = -(-x-y); \/\/ -(-x-y)= x+y, simple mathematics trick\n printf(\"%d\",sum);\n return 0;\n }\n<\/code><\/pre>\n\n\n\n #include<stdio.h>\n int main()\n {\n printf(\"\"Hello World\"\");\/\/ use escape sequence\n return 0;\n }\n<\/code><\/pre>\n\n\n\n #include<stdio.h>\n int main()\n {\n int n=56;\n printf(\"%d\", n>>1);\n }\n<\/code><\/pre>\n\n\n\n #include<stdio.h>\n void reverseStr(char[]);\n void reverseStr(char str[])\n {\n if(str[0]!='')\n {\n reverseStr(str+1);\n printf(\"%c\",str[0]);\n }\n }\n int main()\n {\n char str[] =\"PrepBytes\";\n reverseStr(str);\n return 0;\n }\n<\/code><\/pre>\n\n\n\n int size;\n int arr[size]; \/\/ this is wrong as size is not initialized yet.\n \/\/ The correct code is\n int size;\n scanf(\u201c%d\u201d, &size);\n int arr[size];\n<\/code><\/pre>\n\n\n\n #include <stdio.h>\n #include <string.h>\n int main()\n {\n char str[10]; \/\/ any string greater than 10, will be outside integer range.\n int num = 0, i, j, len;\n printf(\"Enter a number String: \");\n gets(str);\n len = strlen(str);\n for(i=0; i<len; i++){\n num = num * 10 + ( str[i] - '0' );\n }\n printf(\"%d\", num);\n return 0;\n }\n<\/code><\/pre>\n\n\n\n #include <stdio.h>\n #include <string.h>\n int main()\n {\n int num,result,rem,len=0,n,i;\n char str[10];\n printf(\"Enter a number: \");\n scanf(\"%d\",&num);\n n=num;\n while(n!=0)\n {\n len++;\n n=n\/10;\n }\n for(i=0;i<len;i++)\n {\n rem=num%10;\n num=num\/10;\n str[len-(i+1)]=rem+'0';\n }\n str[len]='';\n printf(\"%s\",str);\n return 0;\n }\n<\/code><\/pre>\n\n\nMacros<\/th> Functions<\/th><\/tr> Macro is Pre-processed<\/td> Function is compiled<\/td><\/tr> No type checking is done in Micro<\/td> Type checking is done in function<\/td><\/tr> Use of Micro can lead to side effect at later stages<\/td> Functions do not lead to any side effect in any case<\/td><\/tr> Speed of execution using Micro is faster<\/td> Speed of execution using function is slower<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n