What documentation practices should be followed for PLC programs?

PLC documentation best practices: descriptive tag names (convention: Area_Device_Function), comprehensive tag descriptions, rung comments explaining logic purpose, cross-reference documentation, and version control with change logs. Deliverables: I/O list with termination details, memory map, program printouts with comments, sequence descriptions, P&ID references, and test procedures. Maintain as-built documentation matching installed system. Use PLC software features for automatic cross-referencing and tag usage reports. Store backups in multiple locations. Documentation enables efficient troubleshooting and system modifications.