error non-lvalue in assignment

I get error msg non-lvalue in assignment(mark with red color)

Code:

 // Write a program that asks the user for a 24-hour time,// Then displays the time in 12-hour form:
// CREATED BY: ABHIJIT DAS
// DATE: 28.6.2012


#include<stdio.h>
#include<conio.h>
main()


{
      int hour, min, hour_12;
      
      printf("Enter a 24-hour time(as xx:xx):\n");
      scanf("%d:%d", &hour, &min);
      
     
              
      hour_12 = hour - 12;
      
      if( 0 = hour_12  &&  0 = min)
      {
              printf("The time is 12:00 AM");
              }
     else if(hour <= 24)
      {
      printf("Equivalent 12-hour time: %d:%d", hour_12, min);
      }
     
      else printf("Invaled time");
      if(hour = 0)
      {
              printf("You enter an invaled time");
              }
              
              else if(hour > 0 && hour <= 12)
              {
                   printf("AM");
                   }
                   else if(hour > 12 && hour <= 24)
                   {
                        printf("PM");
                        }
                        else printf("You enter an invaled time");
                        
                        getch();
                        return 0;
                        }

help me. Thanks.

Code:

if( 0 = hour_12  &&  0 = min)

Be careful, you're mixing up the assignment operator (=) and the relational operator (==).

Thanks for your help matticus.