Figure 2.6 Examples of a command line and GUI interface

Operating System Fundamentals
20 Managing System Resources An operating system needs to manage a wide range of system resources. Some of the main resources controlled by the operating system include CPU scheduling and process management, memory (RAM, access to peripheral devices and file system management.

CPU Scheduling
Memory is like a workspace for the information and program instructions that are being used by the computer. The Central Processing Unit (CPU) is the component that actually does the work. The CPU performs all of the program instructions, sends commands to devices, and receives information back from those devices. Just like memory, something needs to regulate which devices and applications get to use the CPU, and for how long. This task is handled by the operating system. Most modern CPUs and operating systems can handle multitasking and multithreading. That is, they can run more than one application at a time and they can process threads from more than one device and application at a time. However, the CPU has limited resources. It needs a schedule of processes to carryout, or nothing will run properly. In older operating systems, it was up to each application to determine how long it needed to use the CPU and what priority it should be given over other applications or interrupts from devices. This was called cooperative multitasking. Unfortunately, this system was rather like having roads with no traffic laws or police officers. If someone wanted to take complete control and cutoff all other traffic, it was possible. Newer operating systems use
preemptive multitasking. That is, the operating system sets out the rules for the use of the CPU and enforces those rules. Preemptive multitasking means that the operating system shares the CPU between everything that needs its attention. It also gives priority to certain devices and applications based on how critical they are to keeping the whole system functioning.
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