READING AND WRITING CLASS OBJECTS FROM/TO FILES

#include
#include
class invt
{
char name[10];
int code;
float cost;
public:
void readdata(void);
void writedata(void);
};

void invt :: readdata(void)
{
printf("Enter Name: "); scanf("%s",&name);
printf("Enter Code: "); scanf("%d",&code);
printf("Enter Cost: "); scanf("%f",&cost);
}
void invt :: writedata(void)
{
printf("%s\t%d\t%f\n",name,code,cost);
}
void main()
{
clrscr();
invt item[3];
fstream file;
file.open("stock.dat",ios::in|ios::out);
printf("Enter the details for three items\n");
for(int i=0;i<3;i++)
{
item[i].readdata();
file.write((char *) &item[i],sizeof(item[i]));
}
file.seekg(0);
printf("\n\t\tOUTPUT\n\n");
printf("Name\tCode\tCost\n");
for(i=0;i<3;i++)
{
file.read((char *) &item[i],sizeof(item[i]));
item[i].writedata();
}
file.close();
getch();
}

OUTPUT:
In the above program object is directly written in to the file but not the elements or the data directly and the data is retrieved by means of the object but not directly.

Enter details for three items
Enter Name: aaaa
Enter Code: 333
Enter Cost: 45
Enter Name: bbbb
Enter Code: 434
Enter Cost: 54
Enter Name: cccc
Enter Code: 535
Enter Cost: 65

OUTPUT

Name Code Cost
aaaa 333 45
bbbb 434 54
cccc 535 65

WRITING NUMBERS IN TO FILE

#include"fstream.h"
#include"conio.h"
void main()
{
Clrscr();
float ht1[4],ht[4]={13,14,54,66};
fstream file;
file.open("aaa.a",ios::out);
file.write((char *) &ht,sizeof(ht));
file.close();
file.open("aaa.a",ios::in);
file.read((char *) &ht1,sizeof(ht1));
for(int i=0;i<4;i++)
{
printf("%f",ht1[i]);
printf("\n");
}
file.close();
getch();
}

OUTPUT:
The numbers in the floating point array ht are first converted into character type and then they are stored in the file with the file name “aaa.a” and then they are retrieved from the file with file name “aaa.a” and stored in the array of floating point ht1 and these values are printed as follows.

13
14
54
66

Finding Even of Odd without decission statements.

This is a program in C to find whether the given number is an even or odd number. But no decission making statements (like if, if-else, switch, while etc..) are employed.

void main()

{

int n;

printf("Enter the n value: ");

scanf("%d",&n);

char res[2];

res[0]='e';

res[1]='o';

printf("%c",res[n%2]);

getch();

}

Output:

Enter the n value: 10

E

here E stands for even number and

O stands for Odd number

Implementation of mini-printf

/* this is a program in C-Language to implement a printf statement*/
#include"stdio.h"
#include "stdarg.h"
int mprintf(const char *str,...);
int main()
{
     mprintf("Text is %d,%c,%d,%f",10,'a',15,2.3);
     return 0;
}

int mprintf(const char *str,...)
{
     int i=0,p;
     float f;
     char c,ch;
     va_list ap;
     va_start(ap,str);
     while(str[i]!='\0')
     {
         if(isalpha(str[i])
         {
             putchar(str[i]);
             i++;
         }
         else if(str[i]=='%')
         {
         i++;
         switch(str[i])
         {
         case 'd': p=va_arg(ap,int);printf("%d",p);break;
//instead of printf here we can use a user defined function that converts the integers into characters and prints
         case 'f': f=va_arg(ap,double);printf("%d",f);break;
//instead of printf here we can use a user defined function that converts the floating point values into characters and prints. to print characters putchar can be used.
         case 'c': c=va_arg(ap,int);putchar(c);break;
         default: putchar("%");putchar(str[i]);break;
     }
     i++;
     }
     else
     {
         puthcar(str[i]);i++;
     }
     }
     return 0;
// we can employ a count value to count the total no of values printed and can be returned here
}