int x;
char c;

x = x + c;
x = x + (int)c;

x: .int 0
c: .fill 1
junk: .int 23432

# wrong method 1
   movl c,%eax
   addl %eax,x
   
# wrong method 2
   movb c,%al
   addl %eax,x
   
# wrong method 3
   movb c,%al
   addb %al,x
   
# obvious wrong method 4
   movl c,%eax
   addb %al,x
   
# right method 1
   movl $0,%eax
   movb c,%al
   addl %eax,x
   
# right method (scenic route) 2
   movb c,%al
   addb %al,x
   adcb $0,x+1
   adcb $0,x+2
   adcb $0,x+3
   


void sub1(int x, int y)
{
  int z;
  
  ...
}


static allocation for parameters
2000 subroutines
30 bytes of parameters for each subroutine

2000*30=60,000 bytes for parameters

on-demand allocation for parameters
2000 subroutines
30 bytes of parameters for each subroutine
max 10 levels of embeded subroutine calls

10*30=300 bytes for parameters