Did Old English use þ and ð like Icelandic does?

No. Old English scribes used þ and ð interchangeably for both th sounds, often mixing them within the same manuscript. The rule that ties þ to the start of a word and ð to other positions is Icelandic. So when you transcribe or search Old English, treat the two letters as equivalent.

What is the ■ at the end of a proof?

It's the end-of-proof mark, often called a tombstone or a Halmos after the mathematician who popularized it, and it takes the place of Q.E.D. Unicode has a dedicated character for it, ∎ (U+220E), though plenty of authors use ■ or the open □ instead. LaTeX's amsthm package prints □ by default at the end of a proof environment.

Why does Alt+0254 give þ instead of ■?

Type Alt+254 without the zero. The leading zero sends the code to the Windows table instead, where 254 is the Icelandic thorn, so no zero-prefixed Alt code will ever produce the square. The short DOS-style code is the only Alt route to it.

Why do my old reports have þ where the bullets were?

The report came from a DOS program that used ■ as its bullet, and Windows-1252 reads that byte as þ. In English text a þ at the start of a line is never a real letter, so a regex replace fixes it safely: in VS Code, open Replace with regex enabled, search for `^þ ` and replace it with `■ ` or `• `.

ASCII 254

Lowercase thornBlack square

ASCII 254 is þ on Windows and ■ in old DOS.

þ (Small Thorn) is byte 254 in Windows-1252, Unicode U+00FE. Icelandic uses it for the voiceless th at the start of words, as in þú (you) and þakka þér (thank you), while ð, the voiced version, appears only inside and at the end of words. ASCII-only systems write it as th, so þú becomes thu. UTF-8 stores þ as C3 BE, and BE is ¾ in Windows-1252, so mangled Icelandic reads Ã¾akka. The HTML entity is þ.

■ (Black Square) is byte 254 in code page 437, the original IBM PC character set, and maps to Unicode U+25A0. It's the last visible character in the set, a solid square smaller than the full block █, and text interfaces used it for bullets, check marks in option lists and the grip on scroll bars. Don't swap in ⬛ (U+2B1B). That one is an emoji: phones draw it in color, and Unicode classes it as wide, so terminals give it two columns and throw off any alignment built on ■. Code page 850 kept ■ here. Windows-1252 has no equivalent, and there's no named HTML entity, so use ■. In UTF-8 it's E2 96 A0.

Latin LetterSymbol

Technical Details

Code Example

</>

#include <stdio.h>

int main(void) {
    /* On Windows (code page 1252) byte 254 is þ.
       Modern terminals expect UTF-8, so print the code point, not the byte. */
    printf("\u00FE\n");   /* UTF-8: C3 BE */

    unsigned char b = 254;         /* the raw Windows-1252 byte */
    printf("%d 0x%02X\n", b, b);    /* 254 0xFE */
    return 0;
}

Code Example

</>

#include <stdio.h>

int main(void) {
    /* Byte 254 is ■ only on a console using code page 437
       (chcp 437 on Windows, or DOSBox). On a UTF-8 terminal the
       lone byte 0xFE is invalid and prints as garbage, often �. */
    putchar(254);

    /* char is signed on x86, so a plain char holding 0xFE is -2.
       Use unsigned char when you compare or index by byte value. */
    char c = (char)254;
    unsigned char u = 254;
    printf("\n%d %d\n", c, u);   /* -2 254 */

    /* Portable: print the Unicode character as UTF-8 instead. */
    printf("\u25A0\n");          /* E2 96 A0 */
    return 0;
}

How to Type It

Windows: Hold Alt and type 0254 on the numeric keypad, with Num Lock on. The leading zero picks the Windows code page. No numeric keypad? In Word, type 00FE and press Alt+X.
Mac: Press Control+Command+Space to open the Character Viewer, then search for "latin small letter thorn".
Linux: In GNOME, or any desktop running IBus, press Ctrl+Shift+U, type fe, then Space. With a Compose key set up, press Compose, t, h.
Phone: Add the Icelandic keyboard in your phone's keyboard settings and type þ there, or tap the character at the top of this page to copy it.

How to Type It

Windows: Hold Alt and type 254 on the numeric keypad, with no leading zero. Windows reads it as a DOS code and inserts ■. No numeric keypad? In Word, type 25A0 and press Alt+X.
Mac: Press Control+Command+Space to open the Character Viewer, then search for "black square".
Linux: In GNOME, or any desktop running IBus, press Ctrl+Shift+U, type 25a0, then Space.
Phone: Phone keyboards have no key for it. Tap the character at the top of this page to copy it.

Frequently Asked Questions

No. Old English scribes used þ and ð interchangeably for both th sounds, often mixing them within the same manuscript. The rule that ties þ to the start of a word and ð to other positions is Icelandic. So when you transcribe or search Old English, treat the two letters as equivalent.
Type Alt+254 without the zero. The leading zero sends the code to the Windows table instead, where 254 is the Icelandic thorn, so no zero-prefixed Alt code will ever produce the square. The short DOS-style code is the only Alt route to it.
The report came from a DOS program that used ■ as its bullet, and Windows-1252 reads that byte as þ. In English text a þ at the start of a line is never a real letter, so a regex replace fixes it safely: in VS Code, open Replace with regex enabled, search for `^þ ` and replace it with `■ ` or `• `.

Frequently Asked Questions

It's the end-of-proof mark, often called a tombstone or a Halmos after the mathematician who popularized it, and it takes the place of Q.E.D. Unicode has a dedicated character for it, ∎ (U+220E), though plenty of authors use ■ or the open □ instead. LaTeX's amsthm package prints □ by default at the end of a proof environment.
Type Alt+254 without the zero. The leading zero sends the code to the Windows table instead, where 254 is the Icelandic thorn, so no zero-prefixed Alt code will ever produce the square. The short DOS-style code is the only Alt route to it.
The report came from a DOS program that used ■ as its bullet, and Windows-1252 reads that byte as þ. In English text a þ at the start of a line is never a real letter, so a regex replace fixes it safely: in VS Code, open Replace with regex enabled, search for `^þ ` and replace it with `■ ` or `• `.

ASCII 254

Lowercase thornBlack square

ASCII 254 is þ on Windows and ■ in old DOS.

Latin Letter

Symbol

#include <stdio.h>

int main(void) {

/* On Windows (code page 1252) byte 254 is þ.

Modern terminals expect UTF-8, so print the code point, not the byte. */

printf("\u00FE\n"); /* UTF-8: C3 BE */

unsigned char b = 254; /* the raw Windows-1252 byte */

printf("%d 0x%02X\n", b, b); /* 254 0xFE */

return 0;

}

#include <stdio.h>

int main(void) {

/* Byte 254 is ■ only on a console using code page 437

(chcp 437 on Windows, or DOSBox). On a UTF-8 terminal the

lone byte 0xFE is invalid and prints as garbage, often �. */

putchar(254);

/* char is signed on x86, so a plain char holding 0xFE is -2.

Use unsigned char when you compare or index by byte value. */

char c = (char)254;

unsigned char u = 254;

printf("\n%d %d\n", c, u); /* -2 254 */

/* Portable: print the Unicode character as UTF-8 instead. */

printf("\u25A0\n"); /* E2 96 A0 */

return 0;

}