Why does this program give the following output?

Question

When I ran this program it gave an output of

1, 4, 4

Why does sizeof('A') gives 4 bytes? Is 'A' treated as integer? If so, then why?

#include<stdio.h>

int main()
{
char ch = 'A';
printf("%d, %d, %d", sizeof(ch), sizeof('A'), sizeof(3.14f));
return 0;
}

Moreover, when I replace

printf("%d, %d, %d", sizeof(ch), sizeof('A'), sizeof(3.14f));

with,

printf("%d, %d, %d", sizeof(ch), sizeof("A"), sizeof(3.14f));

It gives the output

1, 2, 4

which is even more confounding.

P.S.: I used compileonline.com to test this code.

score 4 · Accepted Answer · edited May 23 '17 at 12:28

4

In C, the type of 'A' is int, which explains why sizeof('A') is 4 (since evidently your platform has 32-bit int). For more information, see Size of character ('a') in C/C++

When compiled as C++, the first program prints 1 1 4.

"A" is a string literal consisting of the letter A followed by the NUL character. Since it's two characters long, sizeof("A") is 2.

edited May 23 '17 at 12:28

Community

1
1

answered Feb 08 '14 at 08:09

NPE

486,780
108
951
1,012

Rajdhar · Answer 2 · 2014-02-08T15:43:49.570

1

1.sizeof operator provide the size of input argument.
2.Size of a vaiable is machine(complier) dependent.In you case it is 32 bit.
3.sizeof(ch)=1 because you declare as char.
4.sizeof('A')=4 because compiler treats the literal constant as an integer.
5.sizeof("A")=2 because its a string of 2 bye.In the case string,if u write a single character also compiler insert null character at the end.so its size is 2 bytes.
4.sizeof(3.13f)=4 because its size of float is 4 bytes

edited Feb 08 '14 at 15:43

answered Feb 08 '14 at 09:05

Rajdhar

332
1
4
10

which processor gives `33`bit? – Dipto Feb 08 '14 at 15:41

score 0 · Answer 3 · answered Feb 08 '14 at 08:09

I generally suggest to use sizeof on types or on variables. Using sizeof on literal constants seems confusing (except perhaps on literal strings, to compute 1 + their string length at compile time).

The literal 'A' is in C an int whose size is 4 on your machine.

The literal string "A" is exactly like

   const char literal_A_string[] = {'A', (char)0};

whose size is obviously 2 bytes (because each literal string has a terminal null byte appended).

Why does this program give the following output?

3 Answers3