"Does "8 bit quantities" mean '8 digit quantities'?" digit == numerals 0 to 9 in the decimal system. bit = digits 0 or 1 in the binary system. Although the binary "bit" is a subset of the decimal digit, strictly speaking "8 bit quantities" are not "8 digit quantities", because the two terms refer to two different numeral systems. Here is a random 8 bit quantity (0111 1010) and an 8 digit quantity(21,364,759). The range of integers represented by 8 bits can be 0 (0000 0000) to 255 (1111 1111) for unsigned integers, or from -128( 1000 0000) to 127(0111 1111) for signed integers.

The answer is both yes and no. A bit is a binary digit (base 2, or I think they're calling it "two's complement notation" here) and has either the value 0 or 1. In this case, the quantity 28 in base 10 "translates" to 11100 in the binary number system. Computers like chunks of 8 bits -- called a byte -- so the first three zeroes are placeholders to make a complete byte of 8 bits. Obviously the sequence 00011100 is also "eight digits" in a very literal sense, but the text is clearly talking about computer language. Is that confusing enough? ;-)

It means quantities that can be expressed with 8 bits, i.e. 8 *binary* digits (0 or 1). So that's the range from 0 to 127.

Ah sorry, I misread your title. My mistake.

If you want your English to be corrected, I'm happy to say there are no mistakes here. If you want someone to check your math, you might be in the wrong place, however :)