Combining files line by line

Hi,

I have 2 files say abc and txt,

Contents of abc
A
B
C
D
.
.
.

Contents of xyz

1
2
3
4
.
.
.

I need the output as

A 1
B 2
C 3
D 4
. .
. .

I do not know how many records would be there but both would have same number of records

I am trying to use 2 variables in for(is it possible?)

for i in file1, j in file2
do
echo $i $j
done

This gives error.. Please help.

awk 'FNR==NR{a[NR]=$0;next} {print a[FNR],$1}' file1 file2

What about paste?

$ paste abc xyz
a       1
b       2
c       3
$