I could code you could code he could code we could code you could code they could code
V-ing form
I could be coding you could be coding he could be coding we could be coding you could be coding they could be coding
Perfect
I could have coded you could have coded he could have coded we could have coded you could have coded they could have coded
V-ing perfect
I could have been coding you could have been coding he could have been coding we could have been coding you could have been coding they could have been coding
Negation
Simple form
I couldn't code you couldn't code he couldn't code we couldn't code you couldn't code they couldn't code
V-ing form
I couldn't be coding you couldn't be coding he couldn't be coding we couldn't be coding you couldn't be coding they couldn't be coding
Perfect
I couldn't have coded you couldn't have coded he couldn't have coded we couldn't have coded you couldn't have coded they couldn't have coded
V-ing perfect
I couldn't have been coding you couldn't have been coding he couldn't have been coding we couldn't have been coding you couldn't have been coding they couldn't have been coding
Interrogative form
Simple form
could I code? could you code? could he code? could we code? could you code? could they code?
V-ing form
could I be coding? could you be coding? could he be coding? could we be coding? could you be coding? could they be coding?
Perfect
could I have coded? could you have coded? could he have coded? could we have coded? could you have coded? could they have coded?
V-ing perfect
could I have been coding? could you have been coding? could he have been coding? could we have been coding? could you have been coding? could they have been coding?
Interro-negative form
Simple form
couldn't I code? couldn't you code? couldn't he code? couldn't we code? couldn't you code? couldn't they code?
V-ing form
couldn't I be coding? couldn't you be coding? couldn't he be coding? couldn't we be coding? couldn't you be coding? couldn't they be coding?
Perfect
couldn't I have coded? couldn't you have coded? couldn't he have coded? couldn't we have coded? couldn't you have coded? couldn't they have coded?
V-ing perfect
couldn't I have been coding? couldn't you have been coding? couldn't he have been coding? couldn't we have been coding? couldn't you have been coding? couldn't they have been coding?