The Commodore tape drive is a storage device that stores data sequentially onto standard cassette tapes. The drive contained essentially no internal logic in the device, and was controlled by routines on the C64. There is no form of tape directory and users with tapes containing multiple programs on a single tape would need to rely on the drive’s tape counter, and create their own list as programs were located on the screen and make a note of the current counter number (located on the tape drive unit).
The unit was generally slow to load and save, since the tape motor ran at a set speed, as well as the standard Commodore tape routines would save data twice onto a tape, as a means to prevent data corruption. Some fast loaders such as Turbo Tape replaced the stock tape drive routines, and omitted this double read/write as a method to make access faster.
The tape drive only saw limited sales and usage in the North America markets, as the 1541 floppy drive was more affordable. As a result, most NTSC commercial software was released on floppy disk and not tape. The overseas markets had a higher cost for the 1541 drive, so tape was more commonly used there for many years.
Due to slow loading times, it became common for commercially released programs on tape to have music or even simple games that would be playable while the primary program continued to load (examples are Ocean Loader, or Invade-a-load).
Control of most of the tape drive functions are done using the buttons on the unit to Rewind, Fast Forward, Stop, Play, and Record (pressing both play and record buttons down). Generally you would start with a tape that it rewound to the beginning and then having the C64 search the tape for the content you are looking for. Unless you know the counter mark for a file located later on the tape, in which case you first will fast forward to just before that counter mark and then proceeding to load the file needed. The tape counter has a button on it as well if you need to reset the counter back to 0 (usually when a tape is rewound to its start of the tape).
Typical commands for tape drive usage: (using any of these commands will prompt on the C64 screen to press Play or Play & Record as needed)
LOAD (by itself, will load the first program it comes across)
LOAD “filename” (will search the tape until it comes across the filename you requested. Any program that is located along the way (including the one you are looking for) will be displayed on the screen for a few seconds. If you type a filename that is certain to not exist on the tape, you can easily sit back and note any programs that are located and also the current counter number.)
SAVE “filename” (this will save the current program in C64 memory to tape. It is important to make sure the tape is currently at a place you are ok to save to, as there is nothing to check if it is about to write over an existing program on the tape. Note that some tapes have a leader section at the beginning on the tape that will visually look different than magnetic tape. It is important to make sure the tape is past such if the tape has this feature.)
VERIFY “filename” (this will load the filename specified from tape and compare it with the current program in the C64 memory. This can be handy if after saving, you wish to rewind before the part of tape you just saved to, and confirm the save was successful.
As the tape drive contains no real logic parts inside of it, the most common issues with a drive that fails to save/load are either tape drive motor rubber pully getting old and needs replacement as it no longer can turn the tape at the correct speed (or at all), dirty read/write heads, or the azimuth not being aligned correctly. For dirty r/w heads generally a cotton swap with isopropyl alcohol can be used to gently wipe the heads. For the azimuth alignment, there is a screw inside that can be adjusted. There are programs available that you can run on the C64 to assist when performing the alignment. It would be best to search online for specific guides or videos for more details on how to perform maintenance on the C2N.