hi guys i am totally new in this field. please help me by explanations?

Question

what does it mean?
%d , int, double

#include <stdio.h>

int main() {
printf("int: %d \n", sizeof(int));
printf("float: %d \n", sizeof(float));
printf("double: %d \n", sizeof(double));
printf("char: %d \n", sizeof(char));

return 0;
}

Answer 1

%d is a format specifier which is used to display integer values of the variables or constant numbers to the console

sizeof() operator is used to get the size of particular data type

#include <stdio.h> is a library that contain the definitions of functions like printf(), scanf() etc.

int main() is the main function of a program which is the entry point of all programs, it compulsory in every program

return 0 statement is basically for the compiler, if program executes successfully without any error it returns 0 and if the program has some error it will return 0.
You don't need to write this statement.