char next_char(void){

   char letter='a';

    while(letter!='z'){
            letter=letter+1;
    char next_char(void);
    }
    printf("%c",letter);

}

When the variable letter is static , it has a specific location in the memory and its lifespan is the same with the programm so every time we initialize the variable letter it gets updated.But if its not static the lifespan of the varible letter is the same with the function so i cant find why doesnt this programm run endlessly and it returns each time the same result (z);