Very Simple Circuit but cannot work! Please help.

void initiate_main()
{
trisa=1; porta=0;
trisd=0; portd=0;

}

void main()
{
initiate_main();
while(1)
{
if(porta.f0==1)
{
portd.f0=1;
}

else
{
portd.f0=0;
}
}
}

What's wrong with the programming?