Main.cc: In function ‘int main()’: Main.cc:13:5: error: ‘strupr’ was not declared in this scope strupr(a); ^~~~~~ Main.cc:13:5: note: suggested alternative: ‘strstr’ strupr(a); ^~~~~~ strstr Main.cc:6:10: warning: unused variable ‘b’ [-Wunused-variable] char b[101]; ^ Main.cc:7:10: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(a,100,stdin); ~~~~~^~~~~~~~~~~~~