If memory serves me correctly, a computer system is designed to repeat a task again and again unless there is a change in software or a hardware malfunction. So, a computer controlled drill is told to drill 3cm in a wall, it will drill exactly 3cm time and time again until it told to drill another length or a hardware malfunction occurs (the drill becomes blunt). If this is true, why do random crashes happen? Either the system works and does its job or it doesn't and needs repair. Yet we experience moments when the computer 'sometimes' starts up, or a DVD sometimes loads. Any answer is welcome, Thank You!
What you say would be true if the computer were processing and excuting one process and one process only. The example that you use would be more appropriate for a finite state machine than a multitasking OS. A multitasking OS is more like a busy train lobby with processes entering, operating and exiting. Each customer entering the lobby can be viewed as a task or process which enters the CPU (task starting), does a function (task running), and then exits (task ending) All of the taks communicate with a central operating kernel, which, among other things, is responsible for the modules and tasks that are running. One of the ways that the kernel knows that the task are running correctly is by a mechanism known as a "watchdog timer". The purpose of the watchdog is to ensure that tasks and modules "check in" with the kernel. If a module (for whatever reason) fails to check in, the kernel may take action to restart the module, or in some cases, kill the module. Sometimes the result of killing the module is an unrecoverable error from which the kernel has no other option but to shut down the system. Modules or processes can encounter problems for any number of reasons. Memory access problems (corruption or invalid address) Zombie process (process gets into a loop and doesn't respond) Memory leak (memory not properly released as processes start and stop) Instruction Exception (an abnormal condition which may be caused by poorly written software or an unexpected condition) Others can probably elaborate or add to this list.
anything made or designed by man has hiccups. i have a saying that i tell my customers when they as what caused the problem. i tell them there is 5 things that can go wrong with a system, 1:humans 2:electricity 3:software 4:electronics 5:mechanical. any 1 or a combination of them & god knows what the results will be. with pc's, the operating system is a compromise as it has to work with software manufacturers a to z & hardware manufacturers a to z.
Thank you very much for the replies, particularly 'dailun'. Your explaination was quite easy to understand. Thank You
