Difference Between Computer Science and Programming

Abstraction deals with simplification, indirection deals with location.

• Abstraction is a mechanism that "hides" complicated details of a object in terms of simpler, easier to manipulate terms. In programming, a good example is the difference in details between machine code and the various tools for creating applications that are ultimately based on machine code. Consider creating a Windows Form application with the Visual Studio IDE. The IDE lets you think of the application in terms of easy-to-manipulate items in a What-You-See-Is-What-You-Get manner. The position of a screen widget is abstracted out to a visual location in a frame which you can change by dragging the widget around. Internally, the IDE manipulates the widget using another layer of abstraction such as a high level language (such as C#). C# itself is not manipulated using machine code, it is manipulated using a "Common Runtime Environment" which itself is an abstraction of a computer and operating system.

• Indirection refers to making the location of an item transparent. If you know a web resource's URI, you can access the resource without knowing its precise location. You do not access the resource directly, instead you access through a channel that passes your request through a series of servers, applications and routers. Indirection may be considered to be a special type of abstraction where the location is abstracted.

Yes, the concepts are different.

Simulation

A simulation is a system that behaves similar to something else, but is implemented in an entirely different way. It provides the basic behaviour of a system, but may not necessarily adhere to all of the rules of the system being simulated. It is there to give you an idea about how something works.

Example

Think of a flight simulator as an example. It looks and feels like you are flying an airplane, but you are completely disconnected from the reality of flying the plane, and you can bend or break those rules as you see fit. For example, fly an Airbus A380 upside down between London and Sydney without breaking it.

Emulation

An emulation is a system that behaves exactly like something else, and adheres to all of the rules of the system being emulated. It is effectively a complete replication of another system, right down to being binary compatible with the emulated system's inputs and outputs, but operating in a different environment to the environment of the original emulated system. The rules are fixed, and cannot be changed, or the system fails.

Example

The M.A.M.E. system is built around this very premise. All those old arcade systems that have been long forgotten, that were implemented almost entirely in hardware, or in the firmware of their hardware systems can be emulated right down to the original bugs and crashes that would occur when you reached the highest possible score.