C file that also has assembly code

hi,
I'm writting code (8051) that has both C and assambly in the same file.
for example:
void main()
{
long temp;
#pragma asm
mov a, #0; //assambly
#pragma endasm
temp = a*1000; //C
}

problems:
1. a (acc) is not recognizable in the
C part.what is the BEST thing to do?
2. if I'll continue this proram and add
another asm part will the last value
of a,for example zero, and other
reg/ptr will be saved?