(A1) Simple Batch Systems

Simple Batch systems or just Batch systems process jobs bundled together, leading to an increase in efficiency.

When a job is processed, the system transfers the entire control over to it. Once it is done, the control shifts to the next job, and so on.

This hence, has the following ADVANTAGES:

-maximum processor utilization
-the setup time for jobs is saved
-performance increases, since, the job are sequenced together

It also, however, has a few DISADVANTAGES:

-difficult to debug
-one job affects all the pending jobs.
- job could enter an infinite loop, and others will never be processed.

Hence, we would need some protection scheme for the pending jobs, in case a job is affected/corrupt.

We've heard of applications that run on Windows or Mac and so on. Thus Windows or Mac act as hosts for our computer applications.
Hence, The Operating System is an interface between the user and the hardware, and the host for the applications & software.

Thus, the applications need to access the services of the OS. This is done through what are called APIs(Application Programming Interfaces) or system calls.

The central component of the OS is the kernel. The kernel is the bridge between the applications & the hardware. Hence, It allows applications to process data at the hardware level. It can also control a process' access to the computer memory.

Sometimes, the kernel is used to limit a certain process' access to memory, a phenomenon called memory allocation/protection. This can be achieved by Segmentation & Paging.

The kernel & kernel extentions are alloted certain memory space, which, together with the user space alloted for all user apps, form the Virtual Memory. Virtual Memory is the key to multitasking kernels.