Prague, Czech Republic

Software Systems

Softwarové systémy

Master's
Language: CzechStudies in Czech
Subject area: computer science
Years of study: 2
University website: www.cuni.cz
Software
Computer software, or simply software, is a part of a computer system that consists of data or computer instructions, in contrast to the physical hardware from which the system is built. In computer science and software engineering, computer software is all information processed by computer systems, programs and data. Computer software includes computer programs, libraries and related non-executable data, such as online documentation or digital media. Computer hardware and software require each other and neither can be realistically used on its own.
Software
You can't physically touch software. You can hold a floppy disk or CD-ROM in your hand, but the software itself is a ghost that can be moved from one object to another with little difficulty. In contrast, a road is a solid object that has a definite size and shape. You can touch the the material and walk the route...
Software is a codification of a huge set of behaviors: if this occurs, then that should happen, and so on. We can visualize individual behaviors, but we have great difficulty visualizing large numbers of sequential and alternative behaviors...
The same things that make it hard to visualize software make it hard to draw blueprints of that software. A road plan can show the exact location, elevation, and dimensions of any part of the structure. The map corresponds to the structure, but it's not the same as the structure. Software, on the other hand, is just a codification of the behaviors that the programmers and users want to take place. The map is the same as the structure... This means that software can only be described accurately at the level of individual instructions... A map or a blueprint for a piece of software must greatly simplify the representation in order to be comprehensible. But by doing so, it becomes inaccurate and ultimately incorrect. This is an important realization: any architecture, design, or diagram we create for software is essentially inadequate. If we represent every detail, then we're merely duplicating the software in another form, and we're wasting our time and effort.
George Stepanek (2005) Software Project Secrets: Why Software Projects Fail. p. 10-11
Software
Software is like sex; it's better when it's free.
Attributed to Linus Torvalds at 1996 FSF conference, cited in Doug Abbott (2006) Linux for Embedded And Real-time Applications. p. 1
Software
How can it be that we have so much software that is reliable enough for us to use it? The answer is simple; programming is a trial and error craft. People write programs without any expectation that they will be right the first time. They spend at least as much time testing them and correcting errors as they spent writing the initial program. Large concerns have separate groups of testers to do quality assurance. Programmers cannot be trusted to test their own programs adequately. Software is released for use, not when it is known to be correct, but when the rate of discovering new errors slows down to one that management considers acceptable. Users learn to expect errors and are often told how to avoid the bugs until the program is improved.
Parnas, David L. (Jan 1 1985). "The Parnas Papers". SIGCAS Comput. Soc. 14,15: 27-37. DOI:10.1145/379486.379513.
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