about how bit fields save memory (c + +)

Bit field: First used in the C language later C + + inherits this excellent feature.

For a chestnut: INT--and 4 bytes 2^32 bit, if we only need it to express a 0~16 number,

Using an int is a bit wasteful, so we can use the field 0~16---2^1 ~ 2^5

We can declare it this way: int sudo:5; You can do it!

1 /*2 design a structure to store students ' performance information,3 need to include school number, age and score 3 items, the range of the study number is 0~99 999 999,4 age is divided into four species of Freshman,sophomore,junior,senior,5 scores include A,b,c,d four levels. 6 use bit fields to resolve:7 */8#include <iostream>9 Ten using namespacestd; One  A   enumage{freshman, sophomore, Junior, senior}; -  -   enumgrade{A, B, C, D}; the  -   classStudent { -    Private : -UnsignedintNum: -; +Age:2 ; -Grade GRA:2 ; +     Public  : A        /* Destructors*/ at~student () { -cout<<"student has been Xigou L!"; -        } -        /*constructor Function*/ -Student (unsignedintnum, age, grade GRA); -       voidShow (); in   }  ; -  toStudent::student (unsignedintnum, age, Grade GRA): num (num), age, GRA (GRA) { +    }; -  theInlinevoidstudent::show () { *  $cout<<"The study number is:"<< This->num<<Endl;Panax Notoginseng       stringsag; -       //Take enumeration the       Switch(age) { +            CaseFreshman:sag ="Freshman"; Break ; A            CaseJunior:sag ="Junior"; Break ; the            CaseSenior:sag ="Senior"; Break ; +            CaseSophomore:sag ="Sophomore"; Break ; -       } $cout<<"Age is:"<<sag<<ends; $cout<<"results are:"<<Char('A'+gra) <<Endl; -    } -  the  intMainintargs [],Charargv[]) { - WuyiStudent Stu (12345678, sophomore,c); the stu.show (); -cout<<sizeofstu<<Endl; Wu     return 0; -}

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1 /*2 write a class called CPU that describes the following information for a CPU:3 clock frequency, maximum no more than 3000MHZ = 3000*10^6; Word length, can4 is 32-bit or 64-bit; the number of cores can be single-core, dual-core, or quad-core, whether5 Hyper-Threading is supported. The information requirements are expressed using bit fields. by outputting sizeof6 (CPU) to observe the number of bytes that the class occupies. 7 */8#include <iostream>9#include <string>Ten  using namespacestd; One   //Word length A   enumword{A, b}; -   //Number of cores -   enumKeshu{one, both, four}; the   //whether Hyper-Threading is supported -   enumEs_no{yes, no}; -  -  classintel_cpu{ +    Private : -     //2^29 = 536 870 912 +UnsignedintTp: in ; AWord WD:1  ; atKeshu KS:2 ; -Es_no en:1 ; -     Public : -     //constructor Function -INTEL_CPU (inttp=0, Word Wd=a,keshu ks=two,es_no en=No): - TP (TP), WD (WD), KS (KS), en (en) { incout<<"This is a construct!"<<Endl; -      }; to      // Destructors +~intel_cpu (); -       voidShow (); the  *  }; $intel_cpu::~intel_cpu () {Panax Notoginseng  -cout<<"This is a destructor!! "<<Endl; the     } +  A   voidinline Intel_cpu::show () { the  +cout<<"the clock frequency is:"<<ends; -cout<<tp<<Endl; $cout<<"The word length is "64 or":"; $       if(wd==a) cout<< +<<Endl; -       Elsecout<< -<<Endl; -       Switch(KS) { the          Caseone:cout<<"Single Core"<<endl; Break; -          Casetwo:cout<<"Dual-Core"<<endl; Break;Wuyi          Casefour:cout<<"Four Cores ""<<endl; Break; the         default: cout<<"Shanzhai, no nuclear."; Break; -      } Wucout<<"whether Hyper-threading mode is supported:"<< (En==yes?"Support":"not supported") <<Endl; -   } About  $  intMain () { -  -INTEL_CPU ICP (123456789); - icp.show (); Acout<<sizeoficp<<Endl; +  the}

about how bit fields save memory (c + +)