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Thread & Locks

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Threads Threads are subunits of processes, which can be scheduled independently by the operating system scheduler. Multiple threads can be executed at the same time on a single CPU core. The operating system assigns small slices of computing time to each thread, so that it seems to the user as if multiple tasks are executed at the same time. If multiple CPU cores are available, then multiple threads can be executed truly in parallel. We can either use the POSIX thread API, or the Objective-C wrapper around this API, NSThread. NSThread is a simple Objective-C wrapper around pthreads. Grand Central Dispatch With GCD you don’t interact with threads directly anymore. Instead you add blocks of code to queues, and GCD manages a thread pool behind the scenes. GCD decides on which particular thread your code blocks are going to be executed on, and it manages these threads according to the available system resources. This alleviates the problem of too many threads being cre...
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Opengl-es Buffer

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Framebuffer A  Framebuffer  is a collection of buffers that can be used as the destination for rendering. OpenGL has two kinds of framebuffers: the  Default Framebuffer , which is provided by the  OpenGL Context ; and user-created framebuffers called  Framebuffer Objects  (FBOs). The buffers for default framebuffers are part of the context and usually represent a window or display device. The buffers for FBOs reference images from either  Textures  or  Renderbuffers ; they are never directly visible. Default Framebuffer The Default Framebuffer is the Framebuffer that OpenGL is created with. It is created along with the OpenGL Context. Like Framebuffer Objects , the default framebuffer is a series of images. Unlike FBOs, one of these images usually represents what you actually see on some part of your screen. Framebuffer Object FBO contains a collection of rendering destinations; color, depth and stencil buffer. These logical buff...
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Kernel Startup

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BootLoader GRUB Version 2 (GRUB) Stage 1 :  boot.img  is stored in the master boot record (MBR) or optionally in any of the  volume boot records  (VBRs), and addresses the next stage by an  LBA48  address (thus, the 1024-cylinder limitation of GRUB legacy is avoided); at installation time it is configured to load the first sector of  core.img . Stage 1.5 :   core.img  is by default written to the sectors between the MBR and the first partition, when these sectors are free and available. For legacy reasons, the first partition of a hard drive does not begin at sector 1 (counting begins with 0) but at sector 63, leaving 62 sectors of empty space not part of any partition or file system, and therefore not prone to any problems related with it. Once executed,  core.img  will load its configuration file and any other modules needed, particularly  file system  drivers; at installation time, it is generated from...
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