Beginning x64 Assembly Programming: From Novice to AVX Professional

© Jo Van Hoey 2019

J. Van HoeyBeginning x64 Assembly Programminghttps://doi.org/10.1007/978-1-4842-5076-1_17

17. Bit Manipulations

Jo Van Hoey¹ 

(1)

Hamme, Belgium

 

You already know that you can set or clear bits using bit operations such as and, xor, or, and not. But there are other ways to modify individual bits: bts for setting bits to 1, btr for resetting bits to 0, and bt for testing if a bit is set to 1.

Other Ways to Modify Bits

Listing 17-1 shows the example code.

; bits3.asm

extern printb

extern printf

section .data

      msg1  db   "No bits are set:",10,0

      msg2  db   10,"Set bit #4, that is the 5th bit:",10,0

      msg3  db   10,"Set bit #7, that is the 8th bit:",10,0

      msg4  db   10,"Set bit #8, that is the 9th bit:",10,0

      msg5  db   10,"Set ...