warning: unknown escape sequence: '\!' [enabled by default]<br>
  printf("\\ this is a back-slash character\!\n");<br>
         ^<br>
w1p2.c:25:9: warning: unknown escape sequence: '\!' [enabled by default]<br>
  printf("%% this is a percent sign character\!\n");<br>
         ^<br>
w1p2.c:26:9: warning: unknown escape sequence: '\!' [enabled by default]<br>
  printf("\" this is a double - quote character\!\n");<br>
<br>