Exercises 1

• #include <stdio.h>
  #include <stdlib.h>
  
  int odd(int number){
  /* return 0 if number is even, otherwise return 1 */
    if ( (number/2)*2 == number)
       return 0;
    else
       return 1;
  }
  
  int main(){
  int i;
     i = 7;
     printf("odd(%d) = %d\n",i,odd(i));
  }
  

• #include <stdio.h>
  #include <stdlib.h>
  
  void binary(unsigned int number){
  /* print decimal `number' in binary */
  unsigned int power_of_2;
    power_of_2=1;
    /* Find the greatest power of 2 which isn't more 
       than the number
     */ 
    while (power_of_2<= number)
        if (power_of_2*2>number)
            break;
        else
            power_of_2=power_of_2*2;
  
    /* Now print out the digits */
    while(power_of_2>0){
        if( number/power_of_2 == 1){
          printf("1");
          number = number - power_of_2;
        }
        else
          printf("0");
        power_of_2=power_of_2/2;
    }
    printf("\n");
  }
  
  int main(){
  unsigned int i;
     i=187;
     printf("%d in binary is ",i);
     binary(i);
  }
  

• #include <stdio.h>
  #include <stdlib.h>
  void base(unsigned int number, unsigned int base){
  /* Print 'number' to a specified base */
  unsigned int power_of_base;
    power_of_base=1;
    /* Find the greatest power of 'base' which isn't more 
       than the number
     */ 
    while (power_of_base<= number){
        if (power_of_base*base>number)
            break;
        else
            power_of_base=power_of_base*base;
    }
  
    /* Now print out the digits */
    while(power_of_base>0){
        printf("%1d", number/power_of_base);
        number = number - power_of_base * (number/power_of_base);
        power_of_base=power_of_base/base;
    }
    printf("\n");
  }
  
  int main(){
     base(87,2);
     base(100,8);
  }
  

• #include <stdio.h>
  #include <stdlib.h>
  #define PRIME 1    /* Create aliases for 0 and 1 */
  #define NONPRIME 0
  
  int numbers[1000];
  
  void mark_multiples(int num){
  
  /* Set all elements which represent multiples of num to NONPRIME */
     int multiple = num *2;
     while (multiple < 1000){
       numbers[multiple] = NONPRIME;
       multiple = multiple + num;
     }
  }
  
  
  int get_next_prime(int num){
  /* find the next prime number after `num' */
  int answer;
    answer = num+1;
    while(numbers[answer] == NONPRIME){
      answer= answer + 1;
      if (answer == 1000)
        break;
    }
    return answer;
  }
  
  
  main(){
  int i;
  int next_prime;
  
  /* Set all the elements to PRIME.*/
    for(i=0;i<1000;i++){
      numbers[i] = PRIME;
    }
  
  /* 0 and 1 aren't prime, so set numbers[0] and numbers[1] to false */
    numbers[0] = NONPRIME;
    numbers[1] = NONPRIME;
  
    next_prime = 2;
    do{
      mark_multiples(next_prime);
      next_prime = get_next_prime(next_prime);
    }while(next_prime < 1000);
  
  /* Print out the indices of elements which are still set to PRIME */
    for(i=0;i<1000;i++)
      if (numbers[i] == PRIME)
      printf(" %d  ",i);
    
  
    exit(0);
  }