push    eax
 shl     al,4
        shr     al,4
        cmp     al,0
        pop     eax
 jz      @f
    

test al,0xf    

//pete's original snippet in a HLL (without resorting to GOTO ln)
//ironically/humorously it's less lines in ASM
unsigned char savedByte = originalByte;
originalByte <<= 4;
originalByte >>= 4;
if( originalByte == 0 ){
    originalByte = savedByte;
    ...
}else{
    original = savedByte;
    ...
}

//rev's micro-snippet in a HLL
if( originalByte & 0xf == 0 ){ ... }

//what a novice/beginner might use in a HLL
if( originalByte << 4 == 0 ){ ... }
//or if ignorant of binary (&) and shift (<<) probably modulus
if( originalByte % 16 == 0 ){ ... }
    

aam 16    

Code:

aam 16    

...works if the contents can be modified. ... invalid in long mode.

shl al,4    

mov bl, 0
mov cl, 4
@@:
shr al, 1
adc bl, 0
loop @B    

mov cl,4
    

mov cl,1
shr cl,2
    

instead of

Code:

mov cl,1
shr cl,2    

mov cl,1
shl cl,2    

instead of

Code:

mov cl,1
shr cl,2
    

Aha, four bytes are called a nibble.

Similarly to the terms bit, byte, and nibble, other terms of bit groups of varying sizes have been used over time. All of these are jargon, are obsolete, or are not very common.

* 1 bit: sniff
* 2 bits: lick, crumb, quad, quarter, tayste, tydbit
* 4 bits: nibble, nybble
* 5 bits: nickel, nyckle
* 10 bits: deckle, dyme bag
* 16 bits: plate, playte, chomp, chawmp (on a 32-bit machine)
* 18 bits: chomp, chawmp (on a 36-bit machine)
* 32 bits: dinner, dynner, gawble (on a 32-bit machine)
* 48 bits: gobble, gawble (under circumstances that remain obscure)