(1)
product=1; i=1;
while(i<=n){
product *= i;
i++;
} (2)
i=0;
do {
i++;
} while((i!=n) && (a[i]!=x)); (3)
switch {
case x<y: z=y-x; break;
case x=y: z=abs(x*y); break; // abs()为绝对值函数
default: z=(x-y)/abs(x)*abs(y);
} 
