io.h not found CLion in Ubuntu 20.04

I am trying to run a c++ code however, io.h is not found.

'io.h' file not found

It is shown as

#include <io.h>

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Additionally, I am getting a bunch of weird problems (for a code that is rather > 16 years old):

 Use of undeclared identifier '_read'

or

Unknown type name '__int64'; did you mean '__int64_t'?

or

Use of undeclared identifier '_O_RDONLY'

or

Use of undeclared identifier '_lseeki64'; did you mean 'fseeko64'?

or

Cannot initialize a parameter of type 'FILE *' (aka '_IO_FILE *') with an lvalue of type 'int'

or

Use of undeclared identifier '_lseek'; did you mean 'fseek'?

or

Use of undeclared identifier '_close'

I wonder if these are related to io.h not being found.

$ lsb_release -aNo LSB modules are available.Distributor ID: UbuntuDescription:    Ubuntu 20.04.1 LTSRelease:    20.04Codename:   focal

I have CLion 2020.2.3and

$ gcc --versiongcc (Ubuntu 9.3.0-10ubuntu2) 9.3.0Copyright (C) 2019 Free Software Foundation, Inc.This is free software; see the source for copying conditions.  There is NOwarranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.