awk 'NR==1{hi4=lo4=$4;hi5=lo5=$5}\
    {if ($4>hi4){hi4=$4};if ($4<lo4){lo4=$4};\
     if ($5>hi5){hi5=$5};if ($5<lo5){lo5=$5}}\
    END{print hi4, lo4, hi5, lo5}' cols

96 24 87 23

$ cat ash.txt
1 2 3 45 32
2 3 5 36 87
5 8 3 96 23
8 9 6 24 56

for 4th column: 

$ awk 'min=="" || $4 < min {min=$4} END{ print min}' ash.txt
24

$ awk 'max=="" || $4 > max {max=$4} END{ print max}' ash.txt
96

or

$ awk '
min=="" {
min=max=$4
}
{
if ($4 > max) {max = $4};
if ($4 < min) {min = $4};
}
END {
print "minimum:" min;
print "maximum:" max;
}
' ash.txt

minimum:24
maximum:96

package FileArray;
sub _makeArr{
	$file=shift;
	open FH,"<$file";
	while(<FH>){
		my @tmp=split(" ",$_);
		for($i=0;$i<=$#tmp;$i++){
			$arr[$i][$.-1]=$tmp[$i];
		}
	}
	close FH;
}
sub TIEARRAY{
	my($self,$file)=(@_);
	_makeArr($file);
	return bless \@arr,$self;
}
sub FETCH{
	my($self,$ind)=(@_);
	return $arr[$ind];
}
sub STORE{
	my($self,$ind)=(@_);
	return $arr[$ind];
}
1

use FileArray;
tie @arr,"FileArray","a.txt";
@brr=sort @{$arr[4]};
print "Min: $brr[0] -- Max: $brr[$#brr]\n";