Job Control Languages
Early computer resident monitors and operating systems were relatively primitive and were not capable of sophisticated resource allocation. Typically such allocation decisions were made by the computer operator or the user who submitted a job. Batch processing was common, and interactive computer systems rare and expensive. Job control languages (JCLs) developed as primitive instructions, typically punched on cards at the head of a deck containing input data, requesting resources such as memory allocation, serial numbers or names of magnetic tape spools to be made available during execution, or assignment of filenames or devices to device numbers referenced by the job. A typical example of this kind of language, still in use on mainframes, is IBM's Job Control Language (also known as JCL). Though the format of early JCLs was intended for punched card use, the format survived the transmission to storage in computer files on disk.
As time sharing systems developed, interactive job control emerged. An end-user in a time sharing system could submit a job interactively from his remote terminal, communicate with the operators to warn them of special requirements, and query the system as to its progress. He could assign a priority to the job, and terminate (kill) it if desired. He could also, naturally, run a job in the foreground, where he would be able to communicate directly with the executing program. During interactive execution he could interrupt the job and let it continue in the background or kill it. This development of interactive computing in a multitasking environment led to the development of the modern shell.
Read more about this topic: Job Control
Famous quotes containing the words job, control and/or languages:
“It is not [the toddler’s] job yet to consider other people’s feelings, he has to come to terms with his own first. If he hits you and you hit him back to “show him what it feels like,” you will have given a lesson he is not ready to learn. He will wail as if hitting was a totally new idea to him. He makes no connections between what he did to you and what you then did to him; between your feelings and his own.”
—Penelope Leach (20th century)
“Knowledge in the form of an informational commodity indispensable to productive power is already, and will continue to be, a major—perhaps the major—stake in the worldwide competition for power. It is conceivable that the nation-states will one day fight for control of information, just as they battled in the past for control over territory, and afterwards for control over access to and exploitation of raw materials and cheap labor.”
—Jean François Lyotard (b. 1924)
“It is time for dead languages to be quiet.”
—Natalie Clifford Barney (1876–1972)