Industrial automation incorporates programmable logic controllers in the manufacturing process. Programmable logic controllers (PLCs) use a processing system which allows for variation of controls of inputs and outputs using simple programming. PLCs make use of programmable memory, storing instructions and functions like logic, sequencing, timing, counting, etc. Using a logic based language, a PLC can receive a variety of inputs and return a variety of logical outputs, the input devices being sensors and output devices being motors, valves, etc. PLCs are similar to computers, however, while computers are optimized for calculations, PLCs are optimized for control task and use in industrial environments. They are built so that only basic logic-based programming knowledge is needed and to handle vibrations, high temperatures, humidity and noise. The greatest advantage PLCs offer is their flexibility. With the same basic controllers, a PLC can operate a range of different control systems. PLCs make it unnecessary to rewire a system to change the control system. This flexibility leads to a cost-effective system for complex and varied control systems.
Les nombreux éditeurs d’outils de tests fonctionnels ont des approches différentes. On constate que certains offrent un référentiel contenant une collection d’objets-types que le produit est susceptible de rencontrer dans la majorité des cas. D’un autre côté, certains préfèrent initialiser le référentiel uniquement avec les objets reconnus et utilisés par les différents cas de tests.
An early development of sequential control was relay logic, by which electrical relays engage electrical contacts which either start or interrupt power to a device. Relays were first used in telegraph networks before being developed for controlling other devices, such as when starting and stopping industrial-sized electric motors or opening and closing solenoid valves. Using relays for control purposes allowed event-driven control, where actions could be triggered out of sequence, in response to external events. These were more flexible in their response than the rigid single-sequence cam timers. More complicated examples involved maintaining safe sequences for devices such as swing bridge controls, where a lock bolt needed to be disengaged before the bridge could be moved, and the lock bolt could not be released until the safety gates had already been closed.
Dès que possible, l'homme créa des machines pour automatiser son travail. Si les premières machines ont été conçues pour réaliser une tâche précise (conversions de monnaie, fabrication de tissus, recensement de population,...), seuls les ordinateurs sont capables d'exécuter des travaux très différents. On peut considérer que les tentatives d' […] Lire la suite☛ http://www.universalis.fr/encyclopedie/ordinateurs/#i_2513
Let’s say we want to single out Yellow Pages links. InStr looks for one string inside another, using the format InStr(haystack, needle) and returns the numerical starting point of the first occurence of needle, or 0 if not found. If ‘yp’ or ‘yellowpages’ is found in a link we make the interior of the cell red with the .ColorIndex VBA property, and place a ‘1’ in the cell to the left. FYI, short and simple If...Then statements, like this one: If x = y Then Debug.print "Yo, x is the same as y, bro!", can be written on one line with the closing End If ommitted. If...Then statements are the backbone of any great A.I. … Watson, Wall-E, and now SearchBot()!
I’ve used other automation tools besides VBA. Ubot and iMacros are both excellent, and powerful programs (their own programming languages, really). In some respects they’re easier, and for 99% of web automation tasksg, you really can’t go wrong with either. But I got to where I only used VBA because my programming was getting into Windows API’s and command line calls (Visual Basic is tightly integrated with Windows), plus I often found myself using Excel alongside these programs anyway. I discovered there’s almost nothing VBA can’t do with automating Windows and Internet Explorer (even making IE appear as a different browser), and it seemed to me investing time learning Microsoft’s Visual Basic programming language just made more sense.