Fundamentals of C language -- 2-6 pointers, arrays and sizeof operators

sizeof yes C A language operator （ The main sizeof It's not a function , Although the usage is much like a function ）,sizeof The function of is to return （） The number of memory bytes occupied by the variables or data types inside .

strlen It's a C Library function , Used to return the length of a string （ notes , The length of the string is not calculated at the end of the string ‘/0’ Of ）,strlen The received parameter must be a string .

char str[] = "hello";		sizeof(str)=6		sizeof(str[0])=1		strlen(str)=5
char str[] = "hello";		char *p=str;		sizeof(p)=4				sizeof(*p)=1		strlen(p)=5
int n=10;					sizeof(int)=4		sizeof(n)=4
int b[100];					sizeof(b)=400       // 100*sizeof(int)
void func(int *a) {
     sizeof(a); }		int main(void) {
     int b[100];   }		sizeof(a)=4 			//  The function passes in the address , Not the whole array 

#define dpChar chae * typedef char * tpChar ——  Rename type 
dpChar *p1,p2;					//  an ：char *p1,p2; char *p1; char p2;
tpChar *p1,p2;                //  Equivalent ：char *p1; char *p2;