how to define the "tab" ,"enter" character in a variable(type c)

I want to use the define the "tab" key and

"enter" key in a variable(type c),

But I don't know how to write it :

for example:

data: a1 type c(1).

data: a2 type c(1).

a1 = ?. " the tab key

a2 = ?. " the enter key