Thread: Reading zeros in valid date function

The program below determines if date if valid. It works for all dates without a zero in the number. What am I missing?

Note: Don't worry about leap year. I have not got to that yet, but have a

Code:

#include<stdio.h>

int valid_date(int day,int month, int year)
{
      if ((month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12)
        && (day >= 1 || day <= 31) && (year >= 1900 ))
        return 1;

      else if ((month == 4 || month == 6 || month == 9 || month == 11)
              && (day >= 1 || day <= 30)&& (year >= 1900))
          return 1;

          else
          {
           return 0;
           }
}

int main()
{
int day, month, year;

printf("\nEnter the Day: ");
scanf("%2d",&day);

printf("\nEnter the Month: ");
scanf("%2d",&month);

printf("\nEnter the Year: ");
scanf("%4d",&year);

if(valid_date(day, month, year))
{
printf("\nThis Date is Valid\n");
}
else
{
printf("\nInvalid date Error:  This date doesn't exists in the calander. \n\n ");
}
      system("PAUSE");
      return 0;
}

Review the condition for testing "day of the month" ie 1 <= day <= 30/31.

Think about what constitutes a valid date... The year can be almost anything... The number for the month can be anything 1 to 12. The number of days in a month is your big problem... That I would solve with an array...

Now, try to think in smaller blobs... try to simplify your conditional statements...
For example:

Code:

int IsDateValid(Day,Month,Year)
  { // return 0 for invalid years
     if (Year < 1) 
       return 0;
     // return 0 for invalid months
     if ( (Month < 1) || (Month > 12) )
       return 0;

     // validating the days in a month with array is your task

    return 1; }

See how it's going to return 0 unless it gets all the way to the bottom?
You conditionals are magintudes simpler and the code is far easier to follow.