See(C) Code

#include<stdio.h> int main() {  int n;    printf("Eneter number\n");  scanf("%d", &n);  if( !(n & (n-1))){     printf("%d is power of 2\n", n);     return 0;  }  printf("%d is not power of 2 \n", n);  return 0; }

/*  * C program to Simulate Implementation of  Linux *cat* command  * This program will not handle redirection  * you can try to improve this program to handle redirection of file contents  */ #include<stdio.h> #include<string.h> #define MAX_FILE_NAME_CHARS 255 int main(int argc, char *argv[]) {  FILE *fp;  char file_name[MAX_FILE_NAME_CHARS], ch;  int i;  /*   * after creating a.out, rename it as mycat for our own cat command   * and it usage is same as standard cat command   */  if(argc<1){     printf("Usage mycat <filename> \n");     return 0;  }  /*   * cat handles more than one file   * so we need this loop to handle all the files provided   * on command line   */  for(i=1; i<=argc;i++){     /* no need of copy but for understanding purpose, i have created      * str...

/*  * C99 has  support of variable arguments in macros statement  * (called variadic macro) just like variable argument function, Macros also   * can be of variable number of augments  * This program illustrate variadic macros  */ #include <stdio.h>   /*   * Simple Macro definition   * which allows to print whatever the way you want   *  in Macro definition "..." indicates variadic macro, OP() definition is    * mixture of named args and variable number of aguments, it is possible   * to have macro of complete variable number of args   * like DISPLAY in below example   */ #define OP(format, exp, ...)  printf(format, exp, ##__VA_ARGS__) #define DISPLAY(...)    printf(__VA_ARGS__) int main() {  int a=3, b=4, c=5;  OP("%s %d\n", "Result after add", a+b);  OP("%s %d %s %d\n", "Result after add", a+b+c, "Result after sub", a-b);  OP("%s\n", "This is tes...

/*  * Program to print Armstrong number between range m and n  * Armstrong  number is nothing but sum of cubes of digits of number is  * equal to the number  * ex: 153 is Armstrong number since 1^3+5^3+3^3=153  * there are very few numbers hold above property; execute   * below program to find all numbers  * b/w m and n  */ #include <stdio.h> void is_armstrong(int num) {   int sum=0, n, d;   n=num;   while(n){   d=n%10;  /* extract digits of number*/   sum=sum+(d*d*d);  /*take sum of them */   n=n/10;  }  if(sum == num)  /*sum is same as number then it is Armstrong number*/     printf("%d\n", sum); } int main() { int i,n,m; printf("Enter range \n"); scanf("%d%d", &m, &n);  for(i=m;i<=n;i++){    is_armstrong(i);  } return 0; }

/*  * Program to swap bit in given 32 bit Integer number  */ #include<stdio.h> int main() {  int a;  int b1, b2;  printf("Enter numbers \n");  scanf("%d", &a);  printf("Enter bit numbers to be swapped\n");  scanf("%d%d", &b1, &b2);  if(b1 >=31 || b2>=31){     printf("Invalid bit positions(valid are 0 - 31)\n");     return 0;  }    if((a&(1<<b1)) && !(a&(1<<b2))){     /* bit number b1 is set but b2 is not      * to swap just unset b1 and set b2      */       a=a & ~(1<<b1);       a=a | (1 << b2);  } else if(!(a&(1<<b1)) && (a&(1<<b2))){        /* bit b1 is not set(zero) and bit b2 is set         * so to swap set b1 and clear b2 ...

This is one of the interview question, beginners could note, below is one of the way how we can find size of structure without using sizeof operator in C It is explained with simple program as follows #include<stdio.h> struct test {  int a;  char c;  double d; }; int main() { struct test *p; int size=0; /*  * initialize struct pointer with  * zero after type casting it to of type (struct test *)  */ p=(struct test *)0; /* by adding one to p gives size of struct */ size =(int)(p+1); printf("without using sizeof %d\n", size); /* verify result with sizeof operator */ printf("with using sizeof %d\n", sizeof(struct test)); return 0; } same way we can find size of other variables as well :-)

/*  *Program to find size of text file  */ #include<stdio.h> #define LINE 80 int main(int c, char *argv[]) { /* fp is file pointer, once we open file, it is pointer to opened file */  FILE *fp;  char ch;  unsigned int size=0; /* Open file for reading   * argv[0] is executable program name and argv[1] is first   * argument given after executable file  */  fp=fopen(argv[1],"r");  /* if we get NULL as return value from fopen()   * it means, program is not able to open file or   * file may not existed ? or given file path will be wrong   */  if(fp == NULL){     printf("Can't open file\n");     return 0;  }  /*   * read characters from file and check size   */  while((ch = fgetc(fp)) != EOF){  /* we can add 1 to size every time but better to use sizeof to avoid issues */        size=size+sizeof(ch); ...

shiv@ubuntu:~/ds/list$ cat deln.c /*  * C Program to delete node in the single linked list, when address of the  *previous  node to be deleted is given  */ #include <stdio.h> #include <stdlib.h> struct list {     int d;     struct list *next; }; /*  * function to delete node when just address of the node to be  * deleted is given in the single linked list  */ void deletenode(void **ptr) {   struct list **temp, *del;   if(*ptr == NULL) {      printf("Invalid pointer\n");      return;   }   temp= (struct list **)ptr;   printf("The address of previous node of the node to be deleted is %p data %d\n", *temp, (*temp)->d);   if((*temp)->next && (*temp)->next->next){      /* any node apart from node before last or last node in the list */      (*tem...

shiv@ubuntu:~/ds/list$ cat  tarr_to_sortlist.c  /*  * Program to create sorted list from given unsorted array  */ #include<stdio.h> #include<stdlib.h> #include<malloc.h> #define MAX 10 struct list { int d; struct list *next; }; int main() {  /* example array to test program */  int a[MAX]={4,1,5,6,10,9,3,2,7,8};  int  i;  struct list *head=NULL, *temp, *insert; /*loop to get all array elements*/ for(i=0;i<MAX;i++) { temp= malloc(sizeof(struct list)); if (temp == NULL) {         printf("Can't allocate memory\n");         exit(0); } temp->d = a[i]; temp->next = NULL;    /* first node in list */    if( head == NULL) {       head = temp;    } else {        / * second node in the list */        if( head->next == NULL){   ...

following are the ways to find machine is little endian or big endian , and how to verify my program is working fine? # 1 /* program to find machine is little endian  or little endian */ #include<stdio.h> int main() {  int x=0x12345678;  char *p;  p=(char *)&x;  if(*p == 0x78) {     printf("Little endian \n");  } else {    printf("Big endian \n");  } return 0; } #2 /* another correct way is using unions */ int main() { union e {        int x;        char y; }; union e p1; p1.x=0x12345678; if(p1.y == 0x78) {     printf("Little endian \n");  } else {    printf("Big endian \n"); } return 0; } #3 below is same as #1 with more simplified shiv@ubuntu:~/ds/misc$ /* following is not correct way to find the machine */  #include<stdio.h> int main() { int num=1; if(*(char *)...

shiv@ubuntu:~/ds/list$ cat swap.c /*  * Program to swap values of two variables  * without using temporary variables  */ #include <stdio.h> /*  * swaping values two variables using arithmetic  * operators  */ void swap(int *x, int *y) {   *x = *x + *y;   *y = *x - *y;   *x = *x - *y; } /*  * swaping values of variables using  * XOR oprations  */ void swap_xor(int *x, int *y) {   *x = *x ^ *y;   *y = *x ^ *y;   *x = *x ^ *y; } int main() {  int x, y, a, b;  x=20;  y=30;  swap(&x, &y);  printf("\nafter swap x=%d and y=%d", x, y);  a=50;  b=100;  swap_xor(&a, &b);  printf("\nafter swap a=%d and b=%d\n", a, b); }

/*  * program to demonstrate writing daemon programs in C and linux  * This Daemon print(adds) time or date every minute, depending on  * user choice t or d to syslog file  */ #include <stdio.h> #include <sys/stat.h> #include <syslog.h> #include <fcntl.h> #include <errno.h> #include <unistd.h> #include <time.h> #include <stdlib.h> /*  * parameters to daemon using argc and argv  */ int main(int c, char *argv[]) {  pid_t pid, sid;  char ch;  time_t t;  char  buf[80];  struct tm *ts; /*  * this daemon expects one argument  * as daemon name is count number 1 and one arg to daemon  * so checking for count <2  */  if(c<2) {     printf("usage: <program name> d | t \n");     return 0;  }  ch = argv[1][0];  printf("The choice is %c\n", ch);  if (!((ch =='d') || (ch =...