Combining 2 files

Shell Programming and Scripting
1

i am having 2 files like this

file 1

1,
2,
3,
4,

file2

5,
6,
7,
8,

what i want do is like this

i want to put all the contents for file 2 after file 1,means adding column in file1

output should be like this.

1,5,
2,6,
3,7,
4,8,
2 
paste -d "" file1 file2
3

can we do this every time means

contents of file1

1,5,
2,6,
3,7,
4,8,

content of file3

s1,
s2,
s3,
s4,

the combined the output will be

1,5,s1,
2,6,s2,
3,7,s3,
4,8,s4,

is it possible

plz elaborate meaning of inverted comma in this command

paste -d "" file1 file2
4

man paste

NAME
       paste - merge lines of files

DESCRIPTION
       Write  lines  consisting  of  the sequentially corresponding lines from
       each FILE, separated by TABs, to standard output. With no FILE, or     when FILE is -, read standard input.

       -d, --delimiters=LIST
              reuse characters from LIST instead of TABs
5 
paste -d "" file1 file2 file3(if provided)

The above command should work fine!

6 
awk 'NR==FNR{a[FNR]=$0}NR>FNR{b=a[FNR]FS$0;print b}' file1 file2