Subroutine Calls

Here is how the assembly language calls the subroutine with the address of a struct as a parameter:

	# write out the first struct    
	move    $a0,$s1
	jal     PStruct
	   
	# write out the second struct    
	move    $a0,$s2
	jal     PStruct

And here is how C does this:

	PStruct( empA );  /* Write out the first struct */
	PStruct( empB );  /* Write out the second struct */

Notice how the C subroutine (and the assembly subroutine) is called with a value: the address of a struct.

In C, a subroutine (function) can have a parameter that is a complete copy of a struct, not just a pointer to it. The assembly language equivalent would involve more work than a subroutine that expects a pointer.