Main.cc: In function ‘int main()’: Main.cc:7:2: error: ‘strlwr’ was not declared in this scope strlwr(a); ^~~~~~ Main.cc:7:2: note: suggested alternative: ‘strstr’ strlwr(a); ^~~~~~ strstr Main.cc:6:7: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s%s",a,b); ~~~~~^~~~~~~~~~~~