Main.cc: In function ‘int main()’: Main.cc:10:13: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(str); ^ In file included from /usr/include/stdio.h:862:0, from Main.cc:1: /usr/include/x86_64-linux-gnu/bits/stdio2.h:232:1: note: declared here gets (char *__str) ^~~~ Main.cc:14:17: error: ‘toupper’ was not declared in this scope str[i]=toupper(str[i]); ^~~~~~~ Main.cc:16:17: error: ‘tolower’ was not declared in this scope str[i]=tolower(str[i]); ^~~~~~~ Main.cc:11:5: warning: this ‘for’ clause does not guard... [-Wmisleading-indentation] for(i=0;str[i]!='\0';i++) ^~~ Main.cc:17:7: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘for’ puts(str); ^~~~ Main.cc:7:8: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&t); ~~~~~^~~~~~~~~~~ Main.cc:10:9: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(str); ~~~~^~~~~