Main.cc: In function ‘int main()’: Main.cc:12:4: error: ‘strlwr’ was not declared in this scope c=strlwr(a); ^~~~~~ Main.cc:12:4: note: suggested alternative: ‘strstr’ c=strlwr(a); ^~~~~~ strstr Main.cc:11:7: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s%s",a,b); ~~~~~^~~~~~~~~~~~