Oracle (sqlplus is not recognized as an internal or external command)

There are quite a lot of reasons why you can't run SQL*Plus. Let me say a few words, see if anything of that helps.

• if you installed Oracle database (such as XE) on your computer, you'll have SQL*Plus as it comes by default with every Oracle database server installation

• if you don't have Oracle database on your computer, you could have installed Oracle client software. There are various options available (full or instant client), and you can pick which part of the client you want to install. For example, SQL Loader, and/or export/import utilities, and/or SQL*Plus

• if you already did something of above mentioned things, then directory (which contains SQL*Plus) isn't part of the PATH environment variable. Installer does that for you, but if you modified the PATH and accidentally removed the directory from it, then add it. For example, for my 11gXE installation, it is located in

  C:\oraclexe\app\oracle\product\11.2.0\server\bin
  

  • alternatively, if you don't want to add it to PATH (can't think of any reason why not), change current directory to it and then run SQL*Plus:

    c:\Temp>cd C:\oraclexe\app\oracle\product\11.2.0\server\bin
    
    C:\oraclexe\app\oracle\product\11.2.0\server\bin>sqlplus
    
    SQL*Plus: Release 11.2.0.2.0 Production on Ned Vel 28 11:13:07 2021
    <snip>
    

• furthermore, looking at what your screenshot shows, there's no ORACLE_HOME on your computer; there is, on mine:

  c:\Temp>echo %oracle_home%
  C:\oraclexe\app\oracle\product\11.2.0\server
  

I hope it'll get you started.