Compilare: user.c: In function ‘main’: user.c:22:31: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] is_letter = symbol >= 'A' && symbol <= 'Z' || symbol >= 'a' && symbol <= 'z'; ^ user.c:20:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(input, "%c", &symbol); ^