SAP transaction codes are an easy way of executing SAP functionality, you simply enter the tcode into the command box in the top left-hand corner and then press enter. As well as the actual code you want to execute there are various options available to you which can also be entered into the sap command field to make it perform additional functionality such as creating a new session, using existing session etc. Please see below for a list of these options which uses se80 to demonstrate some of the syntax but this can be replaced with any transaction code you require.
/nse80 - Call a transaction in the same session /*se80 - Call a transaction in the same session and skips the initial screen. /ose80 - Call a transaction in a new session, keeping existing one as it is /n - Ends current transaction ( Caution: Any changes not saved will be lost without warning ) /i - Deletes the current session /o - Generate session list /ns000 - Ends the current transaction and returns to the start menu /nend - Logs off SAP system /nex - Log off SAP system without a confirmation prompt ( Caution: Any changes not saved will be lost ) /h - Start the Debugger /hs - Start System Debugging /ha - Start Debugging but without screen handling