Meaning of different characters

[Kendal zhang]

gen intra_nafta = (ccode=="CAN" | ccode=="MEX" | ccode=="USA") & (pcode=="CAN" | pcode=="MEX" | pcode=="USA")
replace intra_nafta = 0 if year < 1994
label var intra_nafta "1 if trade bewteen nafta members"
gen imp_nafta_rest = (ccode=="CAN" | ccode=="MEX" | ccode=="USA") & (pcode!="CAN" & pcode!="MEX" & pcode!="USA")

I don't understand the difference between the two commands in bold and the usage of "!", "|" and "*".

[Carlo Lazzaro]

Kendal:
welcome to this forum.
See -help operator-.

[Nick Cox]

This rewriting

1. shortens the code

2. may help explain what it does

3. corrects a minor typo

gen intra_nafta = inlist(ccode, "CAN", "MEX", "USA") & inlist(pcode, "CAN", "MEX", "USA")
replace intra_nafta = 0 if year < 1994
label var intra_nafta "1 if trade between nafta members from 1994" 

gen imp_nafta_rest = inlist(ccode, "CAN", "MEX", "USA") & !inlist(pcode, "CAN", "MEX", "USA")

[Kendal zhang]

OK, thank you! I'm new to STATA, and I have a lot to learn.

This rewriting

1. shortens the code

2. may help explain what it does

3. corrects a minor typo

gen intra_nafta = inlist(ccode, "CAN", "MEX", "USA") & inlist(pcode, "CAN", "MEX", "USA")
replace intra_nafta = 0 if year < 1994
label var intra_nafta "1 if trade between nafta members from 1994"

gen imp_nafta_rest = inlist(ccode, "CAN", "MEX", "USA") & !inlist(pcode, "CAN", "MEX", "USA")