No Interrupts, Please!
An application program written to run under a single-tasking OS typically is master of all it surveys. It can communicate with any IO device, any memory location, disable interrupt recognition if it doesn't want to be interrupted, etc. In a single task environment, the program can disable recognition of interrupts if it will not adversely affect its own operation (the only program executing in the system).
If this same program is run under the management of a multitasking OS, however, it can cause severe problems. If permitted to execute a CLI (Clear Interrupt Enable) instruction, the EFlags[IF] bit is cleared to zero and, as result, the processor will no longer recognize interrupt requests originated by IO devices throughout ...
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