How to merge two text files into one file without using cat or sed

Try paste command :

paste -d';' File1 File2 > File3

#!/usr/bin/awk -f
{
  w[FNR][FILENAME] = $0
}
END {
  for (x in w)
    print w[x][ARGV[1]] ";" w[x][ARGV[2]]
}

I also came up with this, but it fails because of the way Awk iterates arrays:

#!/usr/bin/awk -f
{
  w[FNR][FILENAME] = $0
}
END {
  for (x in w) {
    y = 0
    for (z in w[x]) {
      printf w[x][z]
      printf y ? "\n" : ";"
      y = 1
    }
  }
}