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System calls are used by user programs in order get service from the operating system. Some of the popular system calls are we normally use are open, read, write, close, wait, exec, fork, exit, and kill. There are usually 100’s of system call available in OS. For example, Linux has 300+ system calls. Why we […]
Device drivers and OS In the beginning almost all OS were implemented as a single huge kernel with all device drivers included as part of the kernel. If we think further this design make sense, as almost all device drivers require the hardware/resource access and these accesses are provided by being part of the kernel […]
What is a device driver? Device driver is simply a program which executes in kernel mode (unrestricted mode) interacting directly with hardware of the corresponding device. In the previous post we discussed about the different modes (restricted and unrestricted) of operation. They mainly do all the talking/interaction with raw hardware as part OS. Why we need them? […]
As we all know that CPU (micro-processor) executes all the instructions. Most of the modern architectures support at least 2 modes of CPU operation. Even if architecture supports more than 2 modes, they are usually grouped under 2 modes to have compatibility (of OS — across all machines). Mode 1 — Every operation possible is allowed […]
What is a Data Structure? We will not be talking about data structures implementation in this post, but about their usage or choice during programming. As usual lets start from the basic definition. Data Structure is a particular way of storing and organizing data in a computer so that it can be used efficiently. They […]
What is performance testing? Type: Non-Functional testing What is tested?: System’s behaviour under extreme conditions Objective: 3 S’s — Speed, Scalability, Stability Image src: https://www.multidots.com/services/performance-testing/ How it is done? It is typically done with some variations on the load (no.of concurrent users hitting system under test). Each of them have a defined objective. Load Testing: Check for bottlenecks […]
We all know about the standard comparison based sorting algorithms and their time/space complexity. Algorithms like bubble sort, insertion sort, selection sort, quick sort, merge sort, Heap sort operate with a asymptotic lower bound of O(n log n). Also, other unconventional sorting algorithms like Bucket Sort, Counting Sort, Radix Sort run in O(n) We will not talk […]
Have you all heard about the Global Google outage on December 14, 2020, affecting most of the essential services, including Gmail, YouTube, Google Drive, Google Docs, Google Calendar, and Google Play. If not, this blog will benefit you. First, to understand — if you think if this is the first time we had a global […]
What is that update causing this buzz? With WhatsApp’s new update in the first week of Jan 2021, its users across the globe started receiving an in-app notice on its update to terms and privacy policy. The notification read, “By tapping Agree, you accept the new terms and privacy policy, which take effect on 8 […]