Spool File:
According to Tanenbaum, “Spool” is an acronym for simultaneous peripheral operations on-line (though others may consider this a backronym), or as for printers: simultaneous peripheral output on line. Early mainframe computers had, by current standards, small and expensive hard disks.
In computer science, spooling refers to a process of transferring data by placing it in a temporary working area where another program may access it for processing at a later point in time. The normal English verb “spool” can refer to the action of a storage device that incorporates a physical spool or reel, such as a tape drive
The most common spooling application is print spooling: documents formatted for printing are stored onto a buffer (usually an area on a disk) by a fast processor and retrieved and printed by a relatively slower printer at its own rate. As soon as the fast processor has written the document to the spool device it has finished with the job and is fully available for other processes. One or more processes may rapidly write several documents to a print queue without waiting for each one to print before writing the next. Spooler or print management software may allow priorities to be assigned to jobs, notify users when they have printed, distribute jobs among several printers, allow stationery to be changed or select it automatically, generate banner pages to identify and separate print jobs, etc.
Mechanism:
The entire key to spooling is asynchronous processing, where the program is not constrained by the speed of slow devices, particularly printers. Printers are relatively slow peripherals. In comparison, disc devices and particularly CPUs are orders of magnitude faster. Without spooling print data, the speed of program operation is constrained by the slowest device, commonly printers, forcing the program to wait for the mechanical motion of the printer. Professionals say the program is ‘print bound’.
For example, when a city prepares payroll checks, the actual computation may take a matter of minutes or even seconds, but the printing process might take hours. If the program printed directly, computing resources (CPU, memory, peripherals) would be tied up until the program was able to finish. The same is true of personal computers. Without spooling, a word processor would be unable to continue until printing finished. Without spooling, most programs would be relegated to patterns of fast processing and long waits, an inefficient paradigm.
ACH: Automated Clearing House
according to NACHA, is “The ACH Network is a batch processing, store and forward system that provides for the distribution and settlement of electronic credits and debits among participating financial institutions.” An ACH transaction starts with a Receiver authorizing an Originator to issue ACH debit or credit to an account. A Receiver is the account holder that grants the authorization. An Originator can be a person or a company (such as the gas company, a local cable company, or one’s employer). Accounts are identified by the bank’s Routing Number and the account number within that bank.
“…batch processing, store and forward system…” – Unlike Credit and Debit cards which are real time, meaning that you can swipe your card to make a purchase and seconds later, log into your account and see the transaction, ACH is more of an overnight kinda thing. Companies collect and store transactions over the course of a day/week/month, etc. in a batch. They then forward those transactions (in batch form) to their financial institution or a company such as ACH Direct for processing.
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