could decode
Regular verb: decode - decoded- decoded

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could decode
you could decode
he could decode
we could decode
you could decode
they could decode 	I could be decoding
you could be decoding
he could be decoding
we could be decoding
you could be decoding
they could be decoding	I could have decoded
you could have decoded
he could have decoded
we could have decoded
you could have decoded
they could have decoded	I could have been decoding
you could have been decoding
he could have been decoding
we could have been decoding
you could have been decoding
they could have been decoding	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not decode
you could not decode
he could not decode
we could not decode
you could not decode
they could not decode 	I could not be decoding
you could not be decoding
he could not be decoding
we could not be decoding
you could not be decoding
they could not be decoding	I could not have decoded
you could not have decoded
he could not have decoded
we could not have decoded
you could not have decoded
they could not have decoded	I could not have been decoding
you could not have been decoding
he could not have been decoding
we could not have been decoding
you could not have been decoding
they could not have been decoding	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I decode?
could you decode?
could he decode?
could we decode?
could you decode?
could they decode? 	could I be decoding?
could you be decoding?
could he be decoding?
could we be decoding?
could you be decoding?
could they be decoding? 	could I have decoded?
could you have decoded?
could he have decoded?
could we have decoded?
could you have decoded?
could they have decoded? 	could I have been decoding?
could you have been decoding?
could he have been decoding?
could we have been decoding?
could you have been decoding?
could they have been decoding? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not decode?
could you not decode?
could he not decode?
could we not decode?
could you not decode?
could they not decode? 	could I not be decoding?
could you not be decoding?
could he not be decoding?
could we not be decoding?
could you not be decoding?
could they not be decoding? 	could I not have decoded?
could you not have decoded?
could he not have decoded?
could we not have decoded?
could you not have decoded?
could they not have decoded? 	could I not have been decoding?
could you not have been decoding?
could he not have been decoding?
could we not have been decoding?
could you not have been decoding?
could they not have been decoding?