اشتغال الاجزاء مجتمعة - محطات توليد الكهرباء .. الحاسبات تعمل

The operation of the parts combined - Power plants .. Computers work

The operation of the parts of the system combined is controlled by a main program known as the executive program, which adopts the best interruption method and undertakes the tasks of coordination, refutation, sorting, classification and deciding what should be executed. The active part of the executive program is stored in the main computer memory, while a number of programs are stored in the cumulative storage that the executive program calls to the main memory when the need arises to execute them. The magnetic disk has replaced the magnetic cylinder as the preferred cumulative storage in modern equipment, and semiconductor memories have also replaced magnetic ring memories. The storage capacity of the main memory usually ranges between 16,000 and 250,000 words approximately, while the storage capacity of a single magnetic disk exceeds 500,000 words.

The executive program is responsible for maintaining a time calendar for the timing of the various computer functions at a correct actual time, by means of a high-priority interruption signal issued by an electronic clock every second. The executive program usually runs in a loop of instructions, searching for a task to perform and waiting for any interruption signals to arrive. The complete cycle in this loop takes more than three thousandths of a second. When the interruption signal arrives from the electronic clock every second, the executive program brings the calendar program from the cumulative store to the main memo. This program renews a time record that specifies the time in hours, minutes and seconds for each day, and counts the days, months and years. When the calendar program has finished its task, the program returns it. The executive program may return to the cumulative store and this program resumes its work.

If the supervisor in the main control center wants to print all the measurements of the generating station once every ten minutes, he requests this from the computer by means of a touch panel on which he enters coded instructions and then instructs the computer to read them.

Then an interruption signal is issued. If the computer processor is busy with more preferable tasks, it ignores the interruption signal until it is finished

(A simplified diagram of how the executive program works. This program runs in a loop, so if an interrupt signal is issued, the execution moves to the subprogram concerned with this signal, then returns to the executive program after completing all the required assignments. A program may call another program, which may in turn call another program, and so on until the required task is completed.)

These assignments, and if it is not busy with what is more preferable, it immediately responds to this request. The executive program brings a special program from the cumulative store to the main memo, which is the touch panel processing program. This program reads the entered instructions and interprets them as a request to print measurements every ten minutes. The “ten-minute” information is stored in a special location that the time calendar program checks whenever it is executed to see if the ten-minute period has ended. If so, the executive program knows and brings a scanning program from the cumulative store, according to which all the required measurement entries are read and this information is stored in sequential locations in the memo known as the table. This data comes in raw form from the power plant, the computer processes it and prepares it in its final form, then a special stamp program prints it. These operations are repeated every ten minutes until the controller orders it to stop. Also, if the controller wants the computer to display all the information related to the speed of the turbines on the television screen, for example, he enters coded instructions in this regard via the touch panel, and an interruption signal occurs as previously mentioned, to which the computer processor responds at that time by executing the touch panel processing program, which explains to the executive program what is required. Then the scanning program reads the inputs related to the file speed measurements and stores them. However, the executive program then comes with a different program this time that prepares this information to display on the screen and adds to it the information that determines the location of each feature on the screen, then sends all this information to be stored in the display storage shield, so it appears on the screen in the required form as previously mentioned. The executive program realizes that the turbine speed measurements are displayed permanently until the controller requests that they be erased and that it is therefore necessary to renew them, so if the turbine speed changes, the displayed measurements must change as well. Every few seconds the executive program instructs the scanning program to read the relevant inputs and then the display program on the television screen to change any measurements that may have changed. This method is generally followed in carrying out all tasks undertaken by the computer, which may include monitoring the electrical controls in the generating station, calculating the daily operating efficiency of the station and checking all measurements in the station to ensure that they do not exceed certain limits.

The computer can also protect the vital information stored in it from being lost in the event of a power outage. For example, suppose that the power goes out while the computer is performing a certain operation. Under normal circumstances, the information stored in the processor terminals and semiconductor memories is lost. If the power comes back on, the computer cannot resume what it was doing and must be prepared to work again. This can be avoided by equipping the computer with a special circuit that detects the voltage drop when the power goes out and then issues an outage signal that takes priority over all other work the computer is doing. The executive program then turns to executing a special power outage program, according to which all information related to the computer's operating conditions is stored in the main memory. When the power returns, the computer resumes its work without any problems. The computer finds enough time during the power outage to execute the special program for that. Since the supply voltage may take a few tenths of a second to drop from its normal level to the level at which the computer stops working, while the computer executes program instructions at a speed that may reach 500,000 instructions per second, and if the main memory is a semiconductor memory, the computer is provided with accumulators whose capacity is sufficient to operate it during the period of power outage. The voltage drop sensing circuit then operates during the period in which the supply is transferred from the external lines to the accumulators.

(The main control room in the power generation station).