Examples of enumeration and Pointers in C

An example of enumeration and Pointers in C

In summary 1, define an enumeration, using the typedef enum keyword, such as typedef enum{Red,Green,Blue} Color3;

The conversion from enumeration to value, if no representative value is specified, is calculated from 0, such as Color3 c=Red; printf (" % d c); 0 is displayed unless specified as typedef enum{Red=3,Green=5,Blue=10} Color3;

As for the definition of type pointer, * is added to the left of the variable name to indicate that the variable is only a null pointer. If the initial value is needed, it can only be =0 or =NULL(NULL is also 0). The following statement must actually assign a new address or apply for memory before it can be used.

The use of Pointers is also very simple, such as int i=10; * pi = 0; The defined pi pointer is used to refer to pi if pi is used to refer to pi, and *pi is used to refer to the specific value of pi.

Such as:

  int i=10, *pi=0;
   pi= &i ;// & It's taking the address 
   *pi+=5;
   printf("%d",*pi); // 15
   printf("%d",i);    // because pi Point to the i The address of the ,*pi changed ,i Also follow change ,  Is also 15

OK, if the pointer wants to apply for a new memory, you can use malloc, such as:

   #include <malloc.h>
  ...
   int *p=0;
   p=(int*) malloc(sizeof(int)); //  Here for p Pointer to the application 1 Block of actual memory 
   *p=12345; // for p The memory assignment referred to 
   printf("%d",*p); // 12345
   free(p) ;//  Free memory 

OK, then how to transfer pointer parameters, as follows:

     void testP(int *p){
*p+=100;
}
   void main(){
        int i=10;
testP(&i);
testP(&i);
printf("%d", i): // What do you think it is ?
}

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