for char in {A..Z}; do
    mkdir $char
done

for num in {1..100}; do
    mkdir $num
done

mkdir {A..Z}

$ echo pre-{{F..G},{3..4},{m..n}}-post
pre-F-post pre-G-post pre-3-post pre-4-post pre-m-post pre-n-post

$ echo pre-{F..G}{3..4}{m..n}-post
pre-F3m-post pre-F3n-post pre-F4m-post pre-F4n-post pre-G3m-post pre-G3n-post
pre-G4m-post pre-G4n-post

$ echo file{0001..10}
file0001 file0002 file0003 file0004 file0005 file0006 file0007 file0008 file0009
file0010

$ echo file{0001..10..2}
file0001 file0003 file0005 file0007 file0009

mkdir `seq 1 100`

seq 65 90
    | while read foo; do printf "%bn" `printf '\\x%xn' $foo`; done
    | xargs mkdir

perl -e 'foreach (ord "A"..ord "Z") { mkdir chr $_ }'