What happens when a variable is not initialized in main function

when a variable is not initialized in main function it contains garbage value. This can be well seen from the example below.

main() 
{ 
    int x; 
    printf("%d",x); 
   z= sample(); 
}  
sample() 
{ 
    printf("Testing program"); 
}  
Output is  x=80 
Testing program 

The above program prints a garbage value and the output testing program .This is because the variable x is not initialized and so the variable x had garbage value which is printed first then the function sample is called which gave output as testing program.  Thus it is essential to initialize variables in main () function.