c - Incrementing an integer and initialisation placement having a weird effect? -

i have written following 'hangman game'-program in c (was written quick , dirty don't mind code much):

#include <stdio.h>  int main() {     char word[] = "cat";     int amountguessesallowed = 5;     size_t size = sizeof(word)-1; // -1 exclude '\0'      char guessedword[size];     (int i=0; i<size; i++){         guessedword[i] = '_';     }      int lettersguessed = 0;     int totaltimesguessed = 0;     char c;      printf("%s\n", guessedword);     printf("guess %d - enter character: ", totaltimesguessed+1);     scanf("%s", &c);      while (totaltimesguessed < amountguessesallowed) {         for(int i=0; i<size; i++){             if (word[i] == c && guessedword[i] == '_'){                 printf("it matches character @ index %d!\n", i);                 guessedword[i] = c;                 lettersguessed++;                 printf("letters guessed: %d\n", lettersguessed);             }         }         totaltimesguessed++;         if (lettersguessed == size) {             printf("you win!");             return 0;         } else if (totaltimesguessed == amountguessesallowed) {             printf("you lose!");             return 0;         } else {             printf("%s\n", guessedword);             printf("guess %d - enter character: ", totaltimesguessed+1);             scanf("%s", &c);         }     } } 

the issue appears 3 initialisation lines of lettersguessed, totaltimesguessed , c.

if execute program , enter couple of letters you'll notice reason totaltimesguessed-value appears 2, no longer appears incrementing. there don't appear problems lettersguessed-variable.

___ guess 1 - enter character: b ___ guess 2 - enter character: c matches character @ index 0! letters guessed: 1 c__ guess 2 - enter character: j c__ guess 2 - enter character: 

now if swap order of lettersguessed , totaltimesguessed lettersguessed-variable having issue (remains 1)!

___ guess 1 - enter character: c matches character @ index 0! letters guessed: 1 c__ guess 2 - enter character: matches character @ index 1! letters guessed: 1 ca_ guess 3 - enter character:  

finally, if place char c; line before 2 ints:

char c; int lettersguessed = 0; int totaltimesguessed = 0; 

then works expected!

___ guess 1 - enter character: c matches character @ index 0! letters guessed: 1 c__ guess 2 - enter character: matches character @ index 1! letters guessed: 2 ca_ guess 3 - enter character:  

i've tested in xcode gcc.

there must logical explanation this? hunger enlightenment!

you causing undefined behavior in

scanf("%s", &c); 

because "%s" specifier adds terminating nul byte target single char.

instead can try

if (scanf(" %c", &c) != 1)     handleerrorplease(); 

the space before "%c" intentional, eat white space character left previous call scanf.

when undefined behavior occurs, it's layout of program in when it's loaded memory happen, hence changing order of defined variables causes behavior different.