foo.cc: In function 'int main()':
foo.cc:9:5: error: 'A' was not declared in this scope
     A=getchar();
     ^
foo.cc:23:11: error: invalid conversion from 'char*' to 'int' [-fpermissive]
  putchar(a);
           ^
In file included from /usr/include/stdio.h:859:0,
                 from /usr/include/c++/7/cstdio:42,
                 from /usr/include/c++/7/ext/string_conversions.h:43,
                 from /usr/include/c++/7/bits/basic_string.h:6361,
                 from /usr/include/c++/7/string:52,
                 from /usr/include/c++/7/bits/locale_classes.h:40,
                 from /usr/include/c++/7/bits/ios_base.h:41,
                 from /usr/include/c++/7/ios:42,
                 from /usr/include/c++/7/ostream:38,
                 from /usr/include/c++/7/iostream:39,
                 from foo.cc:1:
/usr/include/x86_64-linux-gnu/bits/stdio.h:79:1: note:   initializing argument 1 of 'int putchar(int)'
 putchar (int __c)
 ^~~~~~~

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