Exercise 3.34, 3.35, 3.36 (Deitel: C How to Program 6th Edition)

3.34 (Hollow Square of Asterisks) 

Modify the program you wrote in Exercise 3.33 so that it prints a hollow square. 

C Program:

#include <stdio.h>
int main(){
    int size, i, j;
    size = 5;
    for(i=1; i<=size; i++){
       if(i==1 || i==size){
          for(j=1; j<=size; j++){
             printf("*");
          }
       }
       else{
          for(j=1; j<=size; j++) {
             if(j==1 || j==size) printf("*"); else printf(" ");
          }
       }
       printf("\n");
    }
    system("pause");
}

Output:

3.35 (Palindrome Tester)

A palindrome is a number or a text phrase that reads the same backward as forward. For example, each of the following five-digit integers is a palindrome: 12321, 55555, 45554 and 11611. Write a program that reads in a five-digit integer and determines whether or not it’s a palindrome. [Hint: Use the division and remainder operators to separate the number into its individual digits.]

C Program: 

#include <stdio.h>
int main()
{
  int n, reverse=0, rem,temp;
  printf("Enter an integer: ");
  scanf("%d", &n);
  temp=n;
  while(temp!=0)
  {     rem=temp%10;
     reverse=reverse*10+rem;
     temp/=10;
  }

/* Checking if number entered by user and it's reverse number is equal. */
  if(reverse==n)
      printf("%d is a palindrome.",n);
  else
      printf("%d is not a palindrome.",n);
      system("pause");
  return 0;
}

Output:

3.36 (Printing the Decimal Equivalent of a Binary Number)

Input an integer containing only 0s and 1s (i.e., a “binary” integer) and print its decimal equivalent. [Hint: Use the remainder and division operators to pick off the “binary” number’s digits one at a time from right to left. Just as in the decimal number system, in which the rightmost digit has a positional value of 1, and the next digit left has a positional value of 10, then 100, then 1000, and so on, in the binary number system the rightmost digit has a positional value of 1, the next digit left has a positional value of 2, then 4, then 8, and so on. Thus the decimal number 234 can be interpreted as 4 * 1 + 3 * 10 + 2 * 100. The decimal equivalent of binary 1101 is 1 * 1 + 0 * 2 + 1 * 4 + 1 * 8 or 1 + 0 + 4 + 8 or 13.]

C Program: 

#include <stdio.h> int binary_conversion(int);int main(){   int num, bin;   printf("Enter a decimal number: ");   scanf("%d", &num);   bin = binary_conversion(num);   printf("The binary equivalent of %d is %d\n", num, bin);   system("pause");} int binary_conversion(int num){    if (num == 0)    { return 0; }    else    { return (num % 2) + 10 * binary_conversion(num / 2);  }}

Output: