Program translation

Computer programs written in any language other than machine language must be either interpreted or compiled. An interpreter is software that examines a computer program one instruction at a time and calls on code to execute the operations required by that instruction. This is a rather slow process. A compiler is software that translates a computer program as a whole into machine code that is saved for subsequent execution whenever desired. Much work has been done on making both the compilation process and the compiled code as efficient as possible. When a new language is developed, it is usually at first interpreted. If the language becomes popular, it becomes important to write compilers for it, although this may be a task of considerable difficulty. There is an intermediate approach, which is to compile code not into machine language but into an intermediate language that is close enough to machine language that it is efficient to interpret—though not so close that it is tied to the machine language of a particular computer. It is use of this approach that provides the Java language with its computer-platform independence.

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Operating systems

Further work was required of the operating system with the advent of interactive computing, in which the user enters commands directly at a terminal and waits for the system to respond. Processes known as terminal handlers were added to the system, along with mechanisms like interrupts (to get the attention of the operating system to handle urgent tasks) and buffers (for temporary storage of data during input/output to make the transfer run more smoothly). A large computer can now interact with hundreds of users simultaneously, giving each the perception of being the sole user. The first personal computers used relatively simple operating systems, such as some variant of DOS (disk operating system), with the main jobs of managing the user’s files, providing access to other software (such as word processors), and supporting keyboard input and screen display. Perhaps the most important trend in operating systems today is that they are becoming increasingly machine-independent. Hence, users of modern, portable operating systems like UNIX, Microsoft Corporation’s Windows NT, and Linux are not compelled to learn a new operating system each time they purchase a new, faster computer (possibly using a completely different processor).

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Cybercrime

Computer crime is the use of a computer as an instrument to further illegal ends, such as committing fraud, trafficking in child pornography and intellectual property, stealing identities, or violating privacy. Cybercrime, especially through the Internet, has grown in importance as the computer has become central to commerce, entertainment, and government.Because of the early and widespread adoption of computers and the Internet in the United States, most of the earliest victims and villains of cybercrime were Americans. By the 21st century, though, hardly a hamlet remained anywhere in the world that had not been touched by.

Cybercrime ranges across a spectrum of activities. At one end are crimes that involve fundamental breaches of personal or corporate privacy, such as assaults on the integrity of information held in digital depositories and the use of illegally obtained digital information to blackmail a firm or individual. Also at this end of the spectrum is the growing crime of identity theft. Midway along the spectrum lie transaction-based crimes such as digital piracy, money laundering, and counterfeiting. These are specific crimes with specific victims, but the criminal hides in the relative anonymity.

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