If you run Csound from the command line with the option -z, you get a list of all opcodes. Currently (Csound 5.13), the total number of all opcodes is about 1500. There are already overviews of all of Csound's opcodes in the Opcodes Overview and the Opcode Quick Reference of the Canonical Csound Manual.
This chapter is another attempt to provide some orientation within Csound's wealth of opcodes. Unlike the references mentioned above, not all opcodes are listed here, but the ones that are, are commented upon briefly. Some opcodes appear more than once and in different sections to reflect the different contexts in which they could be used. This guide intends to provide insights into the opcodes listed that the other sources do not.