Can a basic data type be converted into user defined data type in c?

Answer 1

Yes, but it cannot be done in C as intuitively as it can be done in C++:

struct X {

X (const int i): m {i} {} // converts an int to an X [C++ only]

X& operator= (const int i) { m=i; return *this; } // assign an int to an X [C++ only]

int m;

};

Usage:

X x {42}; // construct X from int

x = 0; // assign an int to an X

In C we must use a conversion function:

struct X convert (const int i) { // convert an int to an X

struct X;

x.m = i;

return x;

}

Usage:

struct X x;

x = convert (42);

Answer 2

If you want record a file with specific information, for example: Imagine that you want save a file with information about students, so, imagine what type information you will need keep in your file, you don't need think a lot to imagine something such as: ID, name, address, phone, email. So the ideal use of a defined data in C is through the structure, you can put your data in your structure type and save at file. For example:

#include <stdio.h>

#include <string.h>

#define LEN_REC 38

struct students {

char id[2],

name[10],

address[15],

phone[10],

end;

};

int main()

{

FILE *p;

char Str1[ LEN_REC + 1 ];

struct students Student[3];

int i;

memcpy( (void*) Student[0].id,"01",2);

memcpy( (void*) Student[0].name,"Marcos Bre",10);

memcpy( (void*) Student[0].address,"Queen Street,50",15);

memcpy( (void*) Student[0].phone,"6409940349",10);

Student[0].end = '\0';

memcpy((void*) Student[1].id,"02",2);

memcpy((void*) Student[1].name,"Peter Berl",10);

memcpy((void*) Student[1].address,"Queen Street,10",15);

memcpy((void*) Student[1].phone,"6409940344",10);

Student[1].end = '\0';

memcpy((void*) Student[2].id,"03",2);

memcpy((void*) Student[2].name,"James Carr",10);

memcpy((void*) Student[2].address,"Queen Street,30",15);

memcpy((void*) Student[2].phone,"6409940344",10);

Student[2].end = '\0';

if((p=fopen("Students.dat","w"))==NULL){

printf("Error: Open file !\n");

exit(0);

}else{

fprintf(p,"%s",(char*) &Student[0] );

fprintf(p,"%s",(char*) &Student[1] );

fprintf(p,"%s",(char*) &Student[2] );

fclose(p);

}

/* to list your Students */

if((p=fopen("Students.dat","r"))==NULL){

printf("Error: Open file !\n");

exit(0);

}else{

/* List the Students from the file */

while( fread( (void*) Str1 ,1, LEN_REC , p )){

Str1[ LEN_REC + 1 ] ='\0';

printf("%s\n", Str1 );

}

fclose(p);

}

return 0;

}

Answer 3

No. C is not an object-oriented language so there's no way to provide a conversion constructor for a user-defined type.