Library

An executable is almost always not sufficiently complete for direct execution. Software libraries include collections of functions and functionality that may be embedded in other applications. Operating systems include many standard Software libraries, and applications are often distributed with their own libraries. Since software can be designed using many different programming languages and in many different operating systems and operating environments, software standard is needed so that different software can understand and exchange information between each other. For instance, an email sent from a Microsoft Outlook should be readable from Yahoo! Mail and vice versa.


Computer software has to be "loaded" into the computer's storage (such as a [hard drive], memory, or RAM). Once the software has loaded, the computer is able to execute the software. This involves passing instructions from the application software, through the system software, to the hardware which ultimately receives the instruction as machine code. Each instruction causes the computer to carry out an operation – moving data, carrying out a computation, or altering the control flow of instructions.


Data movement is typically from one place in memory to another. Sometimes it involves moving data between memories and registers which enable high-speed data access in the CPU. Moving data, especially large amounts of it, can be costly. So, this is sometimes avoided by using "pointers" to data instead. Computations include simple operations such as incrementing the value of a variable data element. More complex computations may involve many operations and data elements together.


Software quality is very important, especially for commercial and system software like Microsoft Office, Microsoft Windows, Linux, etc. If software is faulty (buggy), it can delete a person's work, crash the computer and do other unexpected things. Faults and errors are called "bugs." Many bugs are discovered and eliminated (debugged) through software testing. However, software testing rarely – if ever – eliminates every bug; some programmers say that "every program has at least one more bug" (Lubarsky's Law).

All major software companies, such as Microsoft, Novell and Sun Microsystems, have their own software testing departments with the specific goal of just testing. Software can be tested through unit testing, regression testing and other methods, which are done manually, or most commonly, automatically, since the amount of code to be tested can be quite large.


For instance, NASA has extremely rigorous software testing procedures for its Space Shuttle and other programs because faulty software can crash the whole program and make the vehicle not functional, at great expense. The software's license gives the user the right to use the software in the licensed environment. Some software comes with the license when purchased off the shelf, or an OEM license when bundled with hardware. Other software comes with a free software license, granting the recipient the rights to modify and redistribute the software. Software can also be in the form of freeware or shareware. See also License Management.


Software can be patented; however, software patents can be controversial in the software industry with many people holding different views about it. The controversy over software patents is that a specific algorithm or technique that the software has cannot be duplicated by others and is considered an intellectual property and copyright infringement depending on the severity. Some people believe that software patent hinder software development, while others argue that software patents provide an important incentive to spur software innovation