Main.cc: In function ‘int main()’: Main.cc:5:8: 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:6:8: 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: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:10:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < min(strlen(a), strlen(b)); i++){ ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~ Main.cc:5:6: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(a); ~~~~^~~ Main.cc:6:6: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(b); ~~~~^~~