H-File System: 1-Non-volatile memory: Nonvolatile memory can get back stored information even when not powered. Used for secondary storage, or longterm persistent storage. CD, hard-disk (Reading and writing time similar), solid-state drive (no moving mechanical components, no difference for sequential vs. random reading, big difference between reading and writing), ROM, flash, magnetic tape (Natural seq reading and writing, suitable for backup)… 2-File system: file- Contiguous logical addr spaces
...B SYSTEM CALLS. 1-Memory Management: All data in memory before and after processing. All instructions in memory in order to execute. Activities: Optimizing CPU & computer response to users. Keeping track of which parts of memory are currently being used and by whom. Deciding which processes (or parts thereof) and data to move into and out of memory. Allocating and deallocating memory space as needed.. 2-Storage management: Files usually organized into directories. Access control on most systems
...D Process Synchro 1-Determining Length of Next CPU Burst: Can only estimate the length. Can be done by using the length of previous CPU bursts, using exponential averaging. 2-Priority Scheduling: A priority number (integer) is associated with each process. The CPU is allocated to the process with the highest priority (smallest integer = highest priority) SJF is a priority scheduling where priority is the predicted next CPU burst time. Problem of Starvation - low priority processes may never execute
...10-Inverted page tables: One entry for each real page of memory. Entry consists of the virtual address of the page stored in that real memory location, with information about the process that owns that page. Decreases memory needed to store each page table, but increases time needed to search the table when a page reference occurs. Use hash table to limit the search to one or few pagetable entries. G-Virtual Memory: 1-Virtual memory: Separation of physical memory from user logical. Only part of
...1-Operating sys: program that acts as an intermediary between a user and hardware (OS kernel). It runs on a computer and strongly depends on its arquitechture (CPU,bus, devices…) *OS goals: -Execute user programs and make solving user problems easier. -Make the computer system convenient to use. 2-Processor - CPU: Processor executes instructions only from memory. 2 modes of processor: *System mode-privileged (does everything) *Usermode-restricted- special ops disabled (ones tha modify sist), like
...1.Digitalization of telephone channel, quantization distortion (noise): Telephone channel, unidirectional path from 300to3400 bandwidth:3100Hz. Its digitalization with PCM(pulse code mod),if +TDM(time div mult) use+efficiency of transmission paths. PCM converts analogue samples to digital forms (+noise immunity transm). 3 ops(A/D converter) to analogue signal before mult&transm:1Sampling(signal discrete in time, fsampling=1/Ts, sampling theorem fmax=fs/2, for the phone fmax3400,fs = 8000 Hz(
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