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Another such computer was the LEO III, first released in 1961. During batch processing, several different programs were loaded in the computer memory, and the first one began to run. When the first program reached an instruction waiting for a peripheral, the context of this program was stored away, and the second program in memory was given a ...
The address is checked against the contents of the bounds register to prevent a process from accessing memory beyond its assigned segment. The operating system is not constrained by the hardware and can access all of physical memory. This technique protects memory used by one process against access or modification by another.
Without protected memory, it is possible that a bug in one program will alter the memory used by another program. This will cause that other program to run off of corrupted memory with unpredictable results. If the operating system's memory is corrupted, the entire computer system may crash and need to be rebooted. At times programs ...
A computer which may be used to provide services to clients. software Any computer program or other kind of information that can be read and/or written by a computer. single in-line memory module (SIMM) A type of memory module containing random-access memory used in computers from the early 1980s to
Bank 2 is called "shadow". The first 4 KB of this address space is the ROM, and 4 KB is reserved for the on-board I/O ports: the disk controller, the keyboard, the parallel port PIA, the serial port ACIA, and a second PIA chip used for the video system. All memory above the first 16 KB is the same memory as Bank 1. This is the mode of the ...
For simplicity, main memory is called "RAM" (an acronym of random-access memory) and secondary storage is called "disk" (a shorthand for hard disk drive, drum memory or solid-state drive, etc.), but as with many aspects of computing, the concepts are independent of the technology used.
This sequence of operations that stores the state of the running process and loads the following running process is called a context switch. The precise meaning of the phrase "context switch" varies. In a multitasking context, it refers to the process of storing the system state for one task, so that task can be paused and another task resumed.
This instruction moves the contents of one memory location to another memory location combining with the current content of the new location: [2]: 42 [20] Instruction movx a, b (also written a-> b) OP = GetOperation(Mem[b]) Mem[b] := OP(Mem[a], Mem[b]) The operation performed is defined by the destination memory cell.