The execution of a program is frequently punctuated by the necessity of interacting with external hardware, a process managed rigorously by the operating system kernel to ensure stability and efficiency. When a running process requires data from a peripheral device—such as reading from a disk, receiving network packets, or capturing user input—it cannot access the hardware directly. Instead, the process must issue a system call, which triggers a trap that transfers control from the less-privileged user mode into the highly privileged kernel mode. The kernel then initiates the required I/O operation via the corresponding device driver. Because hardware operations are immensely slower than the CPU clock cycle, the processor cannot afford to wait (or poll) for the device to complete its task. Instead, the kernel places the requesting process into a waiting state and allows the CPU scheduler to execute another ready process.