Bitcoin scripts are not C or C++. They are an entirely different language specifically for Bitcoin scripts.

The txid is generated from the transaction. You create the transaction and then hash it in order to get the txid.

With bitcoind, you can use the createrawtransaction rpc to create the raw transaction. Read the help for that command and it explains everything. Then you must sign that transaction using the signrawtransaction rpc and then you can send it with sendrawtransaction.