Learn software concepts: Overview of Reverse Engineering

Reverse engineering is the attempt to recapture the top level specification by analyzing the product - I call it an "attempt", because it is not possible in practice, or even in theory, to recover everything in the original specification purely by studying the product.

Reverse engineering is difficult and time consuming, but it is getting easier all the time thanks to IT, for two reasons:
- Firstly, as engineering techniques themselves become more computerised, more of the design is due to the computer. Thus, recognisable blocks of code, or groups of circuit elements on a substrate, often occur in many different designs produced by the same computer program. These are easier to recognise and interpret than a customised product would be.
- Secondly, artificial intelligence techniques for pattern recognition, and for parsing and interpretation, have advanced to the point where these and other structures within a product can be recognized automatically.

Reverse engineering generally consists of the following stages:
1. Analysis of the product
2. Generation of an intermediate level product description
3. Human analysis of the product description to produce a specification
4. Generation of a new product using the specification.
There is thus a chain of events between the underlying design specification and any intermediate level design documents lying behind the product, through the product itself, through the reverse engineered product description, through the reverse engineered specification, and into the new product itself.

Reasons for reverse engineering:

- Interoperability.
- Lost documentation: Reverse engineering often is done because the documentation of a particular device has been lost (or was never written), and the person who built it is no longer available. Integrated circuits often seem to have been designed on obsolete, proprietary systems, which means that the only way to incorporate the functionality into new technology is to reverse-engineer the existing chip and then re-design it.
- Product analysis : To examine how a product works, what components it consists of, estimate costs, and identify potential patent infringement.
- Digital update/correction : To update the digital version (e.g. CAD model) of an object to match an "as-built" condition.
- Security auditing.
- Military or commercial espionage : Learning about an enemy's or competitor's latest research by stealing or capturing a prototype and dismantling it.
- Removal of copy protection, circumvention of access restrictions.
- Creation of unlicensed/unapproved duplicates.
- Academic/learning purposes.
- Curiosity.
- Competitive technical intelligence.
- Learning.

Overview Of Process

A process is an activity which takes place over time and which has a precise aim regarding the result to be achieved. The concept of a process is hierarchical which means that a process may consist of a partially ordered set of sub-processes. A process is rather abstract. It describes the essentials of the purpose, structure, rationale, roles and timing, leaving plenty of implementation freedom. The power of a process is its abstraction, which enables its application in a wide range of applications, by tailoring its implementation to the specific application. A process can be tailored and elaborated in one or more procedures, which describe cookbook-like what need to be done when and by whom.
The process has been given many definitions for instance :
* A program in Execution.
* An asynchronous activity.
* The 'animated sprit' of a procedure in execution.
* The entity to which processors are assigned.
* The 'dispatchable' unit.
In Process model, all software on the computer is organized into a number of sequential processes. A process includes PC, registers, and variables. Conceptually, each process has its own virtual CPU. In reality, the CPU switches back and forth among processes.
A process goes through a series of discrete process states :
* New State: The process being created.
* Running State: A process is said to be running if it has the CPU, that is, process actually using the CPU at that particular instant.
* Blocked (or waiting) State: A process is said to be blocked if it is waiting for some event to happen such that as an I/O completion before it can proceed. Note that a process is unable to run until some external event happens.
* Ready State: A process is said to be ready if it use a CPU if one were available. A ready state process is runable but temporarily stopped running to let another process run.
* Terminated state: The process has finished execution.

A process in an operating system is represented by a data structure known as a process control block (PCB) or process descriptor. The PCB contains important information about the specific process including :
* The current state of the process i.e., whether it is ready, running, waiting, or whatever.
* Unique identification of the process in order to track "which is which" information. * A pointer to parent process.
* Similarly, a pointer to child process (if it exists).
* The priority of process (a part of CPU scheduling information).
* Pointers to locate memory of processes.
* A register save area.
* The processor it is running on.