Concepts:
While cycle, if instruction, module operator (%)

Text:
Implement a C program that:

• acquires 5 number from the keybord
• computes how many even and odd numbers are inserted
• prints the results of this computation

Solution:

while_cycle_1.c

/* Insert 5 numbers using the keyboard and count how many even and odd numbers have been inserted */
 
#include <stdio.h>
#define NUMBERS 5
 
int main(){
  int n;
  int x;
  int n_even, n_odd;
 
  n=0;
  n_even=0;
  n_odd=0;
 
  while(n<NUMBERS){
    printf("Insert number %d: ", n);
    scanf("%d", &x);
 
    if (x%2 == 0) {
      printf("Even!\n");
      n_even = n_even+1;
    }else{
      printf("Odd!\n");
      n_odd = n_odd+1;
    }      
 
     n = n+1;
  }
 
  printf("EVEN: %d - ODD: %d\n", n_even, n_odd);
 
  return 0;
}

Comments:
The program executes 5 times the block of code inside the while cycle that:

• asks the user to insert a number

  scanf("%d", &x);
 

• checks if the number is even if (x%2 == 0) or odd (branch else of the if instruction)

  if (x%2 == 0) {
      /* Code executed if x is even */
 
  }else{
      /* Code executed if x is odd */
  }
 

• in the case of an even, it increments the variable n_even, otherwise, in the case of an odd number, it increments the variable n_odd
• at the ends of the while cycle the program prints the results

  printf("EVEN: %d - ODD: %d\n", n_even, n_odd);