Strobe: A strobe line is the heart of the parallel port which tells the printer as to when to sample the information of the data lines. Usually it is high and it goes low when a byte of data is transmitted.
Data: These 8 lines carry the information to be printed along with special printer codes which sets the printer in different modes like bold, italics etc.
Acknowledge: This lets the computer know that the character was successfully received and that it's been dealt with.
Busy: This pin is set to high when the printer receives the data from computer and is processing it. Once the printer processes the byte, this pin is set to low indicating the computer to send data.
Paper End: This line will go high when you run out of paper, similar to the paper out light on the printer. This is the way by which the computer will know and lets you known of the problem.
Select: When the select line is at high, the printer is online which means it is ready to receive data. When it's at low the computer will not send any data.
Error: This is a general error line. There is no way of knowing the exact error from this line.
Ground: This is the regular signal ground which is used as a reference for the low signal or logical 0.
