NOP command overview and functions

/*************************************** ******************************
* Author: Samson
* Date: 08/03/2014
* Test Platform:
* Linux Ubuntu 3.2.0-58-generic-pae
* GNU bash, version 4.2.39
**************************************** ****************************/

In computer science, NOP or Noop (no operation or no operation completed MED) is an assembly language instruction, a series of programming statements, or a command in the network transmission protocol that does not perform any valid operations.

NOP is used to execute a command with the same effect as an operand.
NOP commands are usually used to control the time sequence, force memory alignment to prevent pipeline disasters, occupying branch instruction delays), or as placeholders for Program Improvement (or replacing removed commands ).
the simplest NOP block in C language is called an empty statement. It only contains a semicolon.
;
but whether such a semicolon is compiled as a NOP instruction requires you to determine how the compiler compiles, this sentence may have been optimized, but it may not be completely correct.
NOP is generally used to crack the software, such as checking the serial number, software for specific hardware or software requirements, dongle and so on. This is achieved by changing functions and/or subprograms to skip the security check and directly returning the expected detection value. Since the commands in most security check subroutines are discarded, they are replaced by NOP. That is, replace the original code for the check with the NOP command.