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Quiz 1 Notes
Operating Systems Principles (CSCI 340)
Queens College CUNY
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CS340 Quiz 1 Notes
Batch processing = uses FCFS (first come-first serve) job queue ; jobs with similar needs were batched together and run as group; automatically transfers control from 1 job to the next; LITTLE TO NO INTERACTION BETWEEN USER AND JOB ● NOT used anymore ● Examples: transactions of credit cards, generation of bills, processing of input/output in the OS Multi programming = 1 CPU but multiple processes ready for execution while using priority algorithm; priority is given to process that needs resource most ● Timesharing = multiprogramming system that supports multiple terminals, 1 for each active user of system; uses round robin- scheduling algorithm that uses queue to execute process within some time frame (may be complete, may not be); 1 CPU but multiple users Multi processing = many CPUs to increase processing power; share resources such as computer bus, clock, memory and peripheral devices. Boot time process = 1. when computer starts, CPU goes to location in ROM and finds set of instructions. 2. Those instructions are checked by POST (power-on-self-test) 3. CPU goes to second hardware location that had Master Boot Record that points to location of Bootstrap program 4. Bootstrap program executes by CPU 5. Bootstrap program locates kernel and loads kernel into memory Bootstrap program = program that should be executed and its stored in ROM (read-only memory) Modern architecture for us is set of instructions -> POST (power on self test) -> hardware is checked -> master boot record -> point to location of complete bootstrap program Master Boot Record = (MBR) will point into the location of a complete bootstrap program Interrupt vector = memory location of an interrupt handler; list of interrupts that system must take action for. ● Connects ID of interrupt with memory location of an interrupt handler (or executable file) that will handle interrupt Dual-Mode processor = A mode bit is added to hardware of computer to indicate current mode. Has 2 modes- user mode 1 (operation is done on behalf of user) and system mode 0 (operation (also privileged) is done on behalf of OS). Reason for using it is to have system
protected by harmful actions that may occur on user mode. If there’s system call on user mode, system traps into External command = executable code NOT built into shell (ls) Internal command = executable code built into shell (cd) UNIX shells runs like upside-down tree and runs in user mode above kernel, commands are treated as external commands ● Korn shell ● Bourne shell Privileged instruction = instructions that are run in system mode/monitor mode ● Examples: I/O instructions, turning off all interrupts, setting timer, context switching, clearing memory System call = interface between user process (user mode) and operating system (kernel) Layered structure = may be vertical (used for OS) or horizontal (used for Windows NT); modules are stacked on top of each other (hardware on bottom, UI on top) that allows easy debugging from bottom-up but if there’s too many layers, it becomes slow Micro-kernel = tiny kernel that is interface between OS and kernel; acts as messenger between hardware components and perform protection functions; PRO is that it’s easy to debug, CON is that performance is poor since there is inter-layer communication
Quiz 1 Notes
Course: Operating Systems Principles (CSCI 340)
University: Queens College CUNY
