#define A 100
void main() { int b=0; int c=30;
while(1) { b++; if(b>1000) b=0; if(abs(b-c)>10) { #ifdef A #undef A #define A 200 #endif
print("A1= %d",A); } else { #ifdef A #undef A #define A 300 #endif
print("A2= %d",A); }
} }
taget result A1 =200 A2 = 300
I want to ask, Dos the #undef rules meet The C standard specifies? thank you