C + + C + + C language differences the second speaking

//differences in ④:struct type enhancement (c + + version)#include <iostream>using namespacestd;//a struct in C + + is a new type of definition declaration//default access rights for structs in C + + public, unlike classesstructteacher{//char name[20]= "millet";//Error C2536: "Teacher::teacher::name": Cannot specify an explicit initializer for an array      //Error Reason: The above initialization, the allocation of memory space and the initialization of the content. //However, the struct does not allocate memory at the time of type definition, so error, for int age=1; maybe C + + compiler does special processing     Charname[ -]; intAge =1;//in C + +, when a struct is defined, a partial member variable can be assigned an initial value//C + + can be in the structure of the body to define functions;    intGetage () {returnAge ; }    intR; //int s = r*r; Do not make this dangerous definition, because when the teacher variable is defined, it will perform the r*r operation, at this time R may not be assigned a value//At this time S is a dirty data, if you need to use s, then S will not do r*r operation again, cause you never get the correct s value// The best way to write a function    intgets () {returnr*R; }};voidMain () {//in the C + + definition struct, you can use the struct keyword or do not use theTeacher T2; structTeacher T1; printf ("age=%d\n", T1.age); System ("Pause");}

//differences in ④:struct type enhancement (C language version)#include <stdio.h>#include<stdlib.h>#include<string.h>//The C-language struct defines a set of variables that the C compiler does not consider to be a new typestructteacher{Charname[ -]; //int age=1; Error: In the C language structure definition, you can not assign an initial value,    intAge ; //A function cannot be defined in a C language structure    /*int Getage () {return age; }*/};voidMain () {//Teacher T1; In C, defining a struct must use the struct keyword because the C compiler does not consider a struct to be a new type    structTeacher T1; System ("Pause");}

//differences in ⑤:struct type enhancement (c + + version)#include <iostream>using namespacestd;//all variables and functions in C + + must have a type//The default type in C is not legal in C + +//f (i) {//printf ("i=%d\n", I);//}intGo () {printf (""); //Error 1 C4716: "Go": Must return a value//in C + +, the function defines the return value type, so the value of the corresponding type must be returned, or the error will be    return 5;}//Summary://in C + +, int f (), and int f (void) have the same meaning, all of which represent an parameterless function that returns a value of int//C + + More emphasis type, any program element must display the specified typevoidMain () {System ("Pause");}

//differences in ⑤:struct type enhancement (C language version)#include <stdio.h>#include<stdlib.h>#include<string.h>//in C, a function's formal parameter can be set without a type, or the return value can be set without a typef (i) {printf ("i=%d\n", i);}intGo () {printf (""); //Warning warning C4716: "Go": Must return a value//in C, the function defines the return value type and can not return a value of the corresponding type, except that the compiler warns}//Summary://in C, int f (); a function that takes an arbitrary argument with a return value of int//int f (void); Indicates an argument function with a return value of intvoidMain () {//C, from the language compiler does not limit how many parameters can a function f accept? F1,2,3,4,5); System ("Pause");}

//difference ⑥:bool Type (c + + version)#include <iostream>using namespacestd;voidMain () {BOOLb =true; printf ("the size of the bool type is%d bytes \ n",sizeof(BOOL)); //bool Type accounts for 1 bytes of memory space of a small sizeb =4;//type implicit conversion warning C4305: "=": Truncation from "int" to "bool"printf"b=%d\n", b);//Printing 1b =0; printf ("b=%d\n", b);//Printing 0System"Pause");}

C + + C + + C language differences the second speaking