Three ways to use C classic function pointers

Definition mode: Int (*p) (Intx,inty); #include <stdio.h> intsum (intx,inty) {returnx+y} intreduce (Intx,inty) {returnx-y;} intmultiply (Intx,inty) {returnx*y;} Floatdivide (Intx,inty) {if (y==0) return0; else returnx*1.0f/y;} structstudent{intage; floatweight; char*name; void (* STUDENTP ()); } intmain (intargc,constchar*argv[]) {//1. Define function pointer int (*P) (Intx,inty)//2. Initialize p=sum//3. Assignment ints=p (3,2)//4. Print printf ("% D\n ", s);//=5; --------------printf ("Please enter a digital 1,2,3,4\n"); Intnum; scanf ("%d", &num); Switch (num) {case1:p=sum; break, Case2:p=reduce, break, case3:p=multiply, break, case4:p=divide; break;} intresult=p ( 22,2); printf ("%d\n", result); Structure: structstudentstu= (22,88, "Tom", STUDP); printf ("Structural body length =%d", sizeof (Stu)); 1. STU.STUDP; 2. structstu*stp=&stu; (*STP). studp; 3. stp->studp; Return0; }