The Visible(s) command returns a string in which unprintable characters are represented by escaped character codes. This allows you to see the byte values comprising the string when they would be otherwise unprintable. The byte values to be escaped are those determined not printable by the StringTools[IsPrintable] procedure.

Important: The transformation applied by Visible is not reversible.

All of the StringTools package commands treat strings as (null-terminated) sequences of $8$-bit (ASCII) characters.  Thus, there is no support for multibyte character encodings, such as unicode encodings.

$\mathrm{with}\left(\mathrm{StringTools}\right)\:$

Visible( Remove( IsPrintable, Iota( 1 .. 255 ) ) );

$''\backslash 1\backslash 2\backslash 3\backslash 4\backslash 5\backslash 6\backslash 7\backslash 8\backslash 9\backslash 10\backslash 11\backslash 12\backslash 13\backslash 14\backslash 15\backslash 16\backslash 17\backslash 18\backslash 19\backslash 20\backslash 21\backslash 22\backslash 23\backslash 24\backslash 25\backslash 26\backslash 27\backslash 28\backslash 29\backslash 30\backslash 31\backslash 127\backslash 128\backslash 129\backslash 130\backslash 131\backslash 132\backslash 133\backslash 134\backslash 135\backslash 136\backslash 137\backslash 138\backslash 139\backslash 140\backslash 141\backslash 142\backslash 143\backslash 144\backslash 145\backslash 146\backslash 147\backslash 148\backslash 149\backslash 150\backslash 151\backslash 152\backslash 153\backslash 154\backslash 155\backslash 156\backslash 157\backslash 158\backslash 159\backslash 160\backslash 161\backslash 162\backslash 163\backslash 164\backslash 165\backslash 166\backslash 167\backslash 168\backslash 169\backslash 170\backslash 171\backslash 172\backslash 173\backslash 174\backslash 175\backslash 176\backslash 177\backslash 178\backslash 179\backslash 180\backslash 181\backslash 182\backslash 183\backslash 184\backslash 185\backslash 186\backslash 187\backslash 188\backslash 189\backslash 190\backslash 191\backslash 192\backslash 193\backslash 194\backslash 195\backslash 196\backslash 197\backslash 198\backslash 199\backslash 200\backslash 201\backslash 202\backslash 203\backslash 204\backslash 205\backslash 206\backslash 207\backslash 208\backslash 209\backslash 210\backslash 211\backslash 212\backslash 213\backslash 214\backslash 215\backslash 216\backslash 217\backslash 218\backslash 219\backslash 220\backslash 221\backslash 222\backslash 223\backslash 224\backslash 225\backslash 226\backslash 227\backslash 228\backslash 229\backslash 230\backslash 231\backslash 232\backslash 233\backslash 234\backslash 235\backslash 236\backslash 237\backslash 238\backslash 239\backslash 240\backslash 241\backslash 242\backslash 243\backslash 244\backslash 245\backslash 246\backslash 247\backslash 248\backslash 249\backslash 250\backslash 251\backslash 252\backslash 253\backslash 254\backslash 255''$

Visible( Select( IsPrintable, Iota( 1 .. 255 ) ) );

$\mathrm{Visible}\left(''2''\right)$

$''2''$

$\mathrm{Visible}\left(\mathrm{Char}\left(2\right)\right)$

$''\backslash 2''$

s := Visible( Iota( 1 .. 10 ) );

$s≔''\backslash 1\backslash 2\backslash 3\backslash 4\backslash 5\backslash 6\backslash 7\backslash 8\backslash 9\backslash 10''$

$\mathrm{Visible}\left(s\right)$

$''\backslash 1\backslash 2\backslash 3\backslash 4\backslash 5\backslash 6\backslash 7\backslash 8\backslash 9\backslash 10''$