Mã:
 #include <stdio.h>#include <conio.h>#include<string.h> struct Book{    char ISBN[10];    float price;    float value;    int quantity;    }; int i=0,dem=0;float total=0;char c;Book tg;Book sach[100];void input(){    while(1)    {            while(1)            {            fflush(stdin);            printf("ISBN :  ");            float ch= scanf("%s%c",&sach[i].ISBN,&c);            if(ch==0 || c!='
' || sach[i].ISBN<0)            printf("
Input incorrect.
");                    else break;            }    if (sach[i].ISBN ==0)   break; //câu này nó không chiu chay.    else        {            while(1)            {            fflush(stdin);            printf("Price : ");            float ch= scanf("%f%c",&sach[i].price,&c);            if(ch==0 || c!='
' || sach[i].price<0)            printf("
Input incorrect.
");            else break;            }            while(1)            {            fflush(stdin);            printf("Quantity :  ");            int ch= scanf("%d%c",&sach[i].quantity,&c);            if(ch==0 || c!='
' || sach[i].quantity<0)            printf("
Input incorrect.
");            else break;            }        sach[i].value=sach[i].price*sach[i].quantity;        total =total + sach[i].value;                }        i++;        dem++;    }    }void sort(){    for (int i = 0; i < dem-1; i++)        for (int j = i + 1; j < dem; j++)        if (strcmp(sach[i].ISBN, sach[j].ISBN) > 0){            char tmp[11];            strcpy(tmp, sach[i].ISBN);            strcpy(sach[i].ISBN, sach[j].ISBN);            strcpy(sach[j].ISBN, tmp);        }}void output(){               sort();         printf("        Book in tock.
");        printf("        =====================
");        printf("ISBN        Price       Quantity        Value
");        printf("-----------------------------------------------
");        for(i=0; i<dem;i++)        {        printf("%s      ",sach[i].ISBN);                printf("%.2f        ",sach[i].price);        printf("%d          ",sach[i].quantity);        printf("%.2f    
",sach[i].value);        }        printf("                            ___________
");        printf("Total value books in stock              %.3f",total);} main(){    while(1)    {    printf("    Books in Stock Organizer
");    printf("    ========================
");    input();    output();     char choice;        printf("


");        fflush(stdin);        printf("Another run (y)?:");        scanf("%c",&choice);                if(choice=='y')         {         printf("Again.");         }        else        {        printf("Good bye!");        return(choice);        break;        }      }        getch();}