classical life cycle ?

[Alanazi]

hiii guyz

I'm trying to work on classical life cycle which consist of Analysis, design , testing and maintance.

I have ONLY problems with some questions regarding analysis and design, because these question preventing me from continuing my work and i DONT UNDERSTAND THEM OR whatsoever.

these questions are

in the analysis,
1-requirements for both the system and the software ?
what are the requirement what does that mean !

2- and interfaceing software with hardware ?
what do we mean by interfacing !



I need explanations for these questions i dont need anything else i stuck with these i have not idea please guyz any one is familar with these question please just explain with EXAMPLES, DO NOT DO ANYTHING ELSE.


thanks

[claudiu]

Requirements are attributes a system(or the environment it operates in) shall have. A good way to think of this is to answer the question: "what will the system do?". An example of a requirement for a software billing system at a supermarket can be:

The system shall print the list of items purchased and the amount owed by the customer on a paper receipt.

There are a ton of types of requirements out there and even a profession requirement engineering dedicated to their study.

Interfacing software with hardware probably refers to the fact that software utilizes hardware (as well as other software) through abstractions called interfaces. For example a program might play a sound by invoking some system function to play a sound file without having to worry about the type of soundboard used by the system, the edition of the driver or how it operates. The operating system acts as an interface for the rest of the software hiding the complexity of the hardware devices.

[Alanazi]

that is really helpfull man, for the first question, however, the second one i'm not quite sure about it.
just explain alittle bit more please.

thank you soo much

[claudiu]

Ok, here is an analogy of an interface.

When you drive a car, in order to break, you hit the break pedal, which is AN INTERFACE between the car breaking system and the driver. As a driver you don't need to understand how the little breaking plates attach to the wheels to provide friction and slow down the car. All you need to know is that if you press that pedal, the car will slow down and eventually halt. The pedal is an abstraction or an interface of the complex breaking mechanism of the car.

Similarly, an operating system is an interface between the hardware of the machine and the software running on it. The operating system hides the complexity of all the devices you have in your computer from the programmer and provides an INTERFACE to them. The example I gave you involving playing a sound relates to this. You can write a very quick program to play a sound file without having to worry how your computer actually creates the sound. The operating system will give you an interface to that such as a function you can use in your code PlaySound().