CSUMB Learning Journal (Chris - Group 1)

  What to Write in your Journal Entry  Write a 1 - 2 paragraph description of what you learned this eighth week in CST 334 Topic: persistence - as it applies to Operating Systems as well as it applies to a CST 334 SCD Online student to complete this course~ In computer science, persistence refers to the characteristic of state of a system that outlives (persists more than) the process that created it. This is achieved in practice by storing the state as data in computer data storage. In life, persistence refers to the characteristic of firm or  obstinate   continuance  in a course of action in  spite  of difficulty or opposition. Applying to operating systems:     Persistence is a vital aspect of operating systems due to the general use case computers have developed into. It would be incredibly hard to use a computer if every time you switched programs or turned the unit off your data would disappear. Computers used to behave in a way li...

  What to Write in your Journal Entry  Write a 1 - 2 paragraph description of what you learned this seventh week in CST 334 Topic: persistence. This weeks primary topic covered persistence. The specific pieces of hardware this dealt with was physical storage devices such as hard drive disks. These devices are considered persistent storage devices due to their ability to retain information even if the system is powered off. The primary example used in this module was a mechanical hard drive. These function by using a rotating plater that has magnetic elements on either side which are manipulated or read by an arm. Past this, this module also covered file system hierarchies and how digital file structures are handled on a physical disk. This included information on files, directories, links, etc.

  What to Write in your Journal Entry  Write a 1 - 2 paragraph description of what you learned this sixth week in CST 334 Topic: semaphores This week was light on material but what we did have focused on semaphores. Semaphores are integers that are used to manage synchronization between threads. They are commonly used to manage critical sections between threads. Operating systems generally provide 2 methods alongside semaphores. Those being acquire and release methods such as SEM_POST and SEM_WAIT. Calling the SEM_WAIT method decrements the semaphore by 1 which then causes any other threads that call that same method to be blocked until the original thread calls the SEM_POST method which increments the semaphore and wakes a waiting thread.

  What to Write in your Journal Entry  Write a 1 - 2 paragraph description of what you learned this fifth week in CST 334 Topic: Concurrency This weak took a look into multi-threading. Previously we covered how a CPU switches between multiple programs running at the same time -- with each program being allocated their own memory section, in contrast, different threads work on the same program and each share a memory space but each thread has its own individual stack. Past this we covered the possible difficulties with threads such as the threat of race conditions. Followed by the topic of locks which can help mitigate issues with threads being scheduled at almost random times by the OS.

  Write a 1 - 2 paragraph description of what you learned this fourth week in CST 334 Topic: Memory Virtualization This week covered further into how memory is handled virtually in the OS, even with including information related to physical disk memory instead of only system memory such as RAM. We covered some ways that an OS can handle allocating and freeing memory in order to prevent wasted space or what is called fragmentation. Another topic covered this week is how virtual addresses are exactly translated into physical addresses -- which is accomplished through the use of Page Tables. This translation of virtual to physical addresses can be costly when executed often, and so TLB tables are utilized to cache translations with the idea that they may be referenced again.