System Programming

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 […]