ioDraw is a free online drawing software, which is used to make flow chart, mind map, Gantt chart, whiteboard hand drawing, topology diagram, organization chart, UML, ER and sequence diagram, graphic design diagram, electronic circuit diagram, etc. it can be used without registration
GitHub: https://github.com/ixiaoyang8/iodraw/releases
Baidu Netdisk: https://pan.baidu.com/s/1T03izdWtRSeMqOXoT9HCug, extraction code: draw