High eight bits and low eight bits: in memory, a unit is one byte, which is 8 bits. If it is a 16-bit instruction, it is to operate two consecutive memory addresses at the same time, and treat these two consecutive memory addresses as a unit, so there are 8 high-order bits and 8 low-order bits.

Because the computer only recognizes the numbers described in binary, for a memory address, that is, an 8-bit binary, such as: 0000 00 1 0000, it is the upper four digits, and 0 00 1 is the lower four digits.

Of course, the two memory addresses are 16-bit binary, that is, 000000010000002. 0000 000 1 is high eight, and 000000002 is low eight.

Each of the eight bits is divided into four high and low bits. For example:1010011101,converted into 1065438. 000 1- 1( 10 radix)-1( 16 radix), so its upper eight bits are A 1 and its lower eight bits are F5.

Extended data:

How to find the upper four digits and the lower four digits in the ascII code table in C language;

Ascii code is stored in C language as char type, and a char occupies one byte, that is, 8 bits.

When written in a binary expression, it is the eight digits of 0 or 1. Of these eight people, the four on the left are called high four, and the four on the right are called low four.

Therefore, when looking up the ascii code table, you need to:

1, converting the value to be checked into a binary value;

2, acquiring a high four-digit value and a low four-digit value;

3. Look up the table according to the high four digits and find the column;

4. Look up the table and find the line according to the low four digits;

5. The cross grid of columns is the character to be searched.