Data Type (Programming)

Question

#include <stdio.h>
 
int main()
{
   long int a = 0x7fffffff * 0x7fffffff;
   long int b = 0x7fffffff * 0x7fffffffl;
   printf("a = %ld, b = %ld\n", a, b);
   return 0;
}

What will be output if sizeof(int) is 4 and sizeof(long int) is 8.

Comments

for a i think it should be 1. but i am not sure for b as there is a l in the second value of product. @srestha mam can u explain

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@Arvin, l means long

Answer 1

Basic Point :- 

let take b=5,c=2

float a = b/c ====> a=2.0 why?

because by precedence and associativity, (float a) = (b/c) ===> equal operator is right associative, therefore (b/c) evaluates first

b and c are integers ===> after evaluating b/c, it will convert to int and returns 2

if atleast either one of the b and c are float ===> after evaluating b/c, it will convert to float and returns 2.5

 

long int a = 0x7fffffff * 0x7fffffff;

0x7fffffff * 0x7fffffff ==> ( 3FFFFFFF00000001 )_H it is long int but our operands are int, therefore convert into int ===> ( 00000001 )_H . ===> long int a = ( 00000001 )_H  = ( 1 )₁₀

 

long int b = 0x7fffffff * 0x7fffffffl;

0x7fffffff * 0x7fffffff ==> ( 3FFFFFFF00000001 )_H it is long int but one of our operands is long int, therefore convert into long int ===> ( 3FFFFFFF00000001 )_H . ===> long int b = ( 3FFFFFFF00000001 )_H = ( 4611686014132420609 )₁₀

Comments

but I still not understand clearly, :( Can u tell more ?

why 2.56 not float? and why we specify L in the constant?

got this https://www.quora.com/What-is-the-difference-between-float-and-double-in-C-language-How-is-it-stored-in-the-memory

but still not clear

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why 2.56 not float?

as per C standards,

any real value treat as double

( i don't know exact reason, but i think, float have less precision than double, for more accuracy they treat every real value as double )

 

why we specify L in the constant?

normally constants are integers only, by adding L in the constant, we are declaring that constant is long int

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thanks :)