CODEWITHSUNDEEP
arrayspointersassembly
Franc
Franc

Reputation: 450

How a character array is stored if initialized as Array[] = "testit"

I have a character array initialized as follows

int main()
{
   char ptr1[] = "testit";
}

has an assembly equivalent

main:
        push    rbp
        mov     rbp, rsp
        mov     DWORD PTR [rbp-7], 1953719668   ; These lines form the string "testit"
        mov     WORD PTR [rbp-3], 29801         ; These lines form the string "testit"
        mov     BYTE PTR [rbp-1], 0             ; These lines form the string "testit"
        mov     eax, 0
        pop     rbp
        ret

I would like to know how the the character array is stored? What are these numbers(in assembly 1953719668 , 29801, 0) referencing to (or how these numbers are calculated) ?

Upvotes: 1

Views: 61

Answers (1)

Erik Eidt
Erik Eidt

Reputation: 26656

The first number, 1953719668, is also 0x‭74736574‬ converted to hex.

Written as separate bytes, in little endian ordering, we have 0x74, 0x65, 0x73, 0x74.

Using ascii we have t, e, s, t.

The 2nd number encodes "it" similarly but in only 16 bits for the 2 characters: 29801 = 0x7469, converted to hex, and to bytes little endian: 0x69, 0x74: i, t.

The last byte is the null terminating byte used by C strings.

http://www.asciichars.com/_site_media/com_photogallery/ascii-chars/xl/ascii-chars-table-landscape.jpg

Upvotes: 2

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