Main.cc: In function ‘int main()’: Main.cc:6:8: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(a); ^ In file included from /usr/include/stdio.h:862:0, from /usr/include/c++/7/cstdio:42, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:46, from Main.cc:1: /usr/include/x86_64-linux-gnu/bits/stdio2.h:232:1: note: declared here gets (char *__str) ^~~~ Main.cc:7:8: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(b); ^ In file included from /usr/include/stdio.h:862:0, from /usr/include/c++/7/cstdio:42, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:46, from Main.cc:1: /usr/include/x86_64-linux-gnu/bits/stdio2.h:232:1: note: declared here gets (char *__str) ^~~~ Main.cc:8:2: error: ‘strupr’ was not declared in this scope strupr(a); ^~~~~~ Main.cc:8:2: note: suggested alternative: ‘strstr’ strupr(a); ^~~~~~ strstr Main.cc:6:6: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(a); ~~~~^~~ Main.cc:7:6: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(b); ~~~~^~~