ITS 235- Windows Operating Environment

1) Name two differences between logical and physical addresses.

2) Consider a system in which a program can be separated into two parts: code and data. The CPU knows whether it wants an instruction (instruction fetch) or data (data fetch or store). Therefore, two base“ limit register pairs are provided: one for instructions and one for data. The instruction base “limit register pair is automatically read-only, so programs can be shared among different users. Discuss the advantages and disadvantages of this scheme.

3) Consider a logical address space of 64 pages of 1024 words each, mapped onto a physical memory of 32 frames.
a. How many bits are there in the logical address?
b. How many bits are there in the physical address? describe a mechanism by which one segment could belong to the address space of two different processes.

4) Describe the mechanism by which one segment could belong to the address space of two different processes.

5) Discuss the impact of internal and external fragmentation in the operating system performance?

SAMPLE SOLUTION

ITS 235- Windows Operating Environment

Question One

Addresses are an important aspect in the CPU memories as they are used to uniquely identify the location of the file or other things that are stored inside the CPU.  The addresses are divided into two main types including the logical address and the physical address. The two addresses have different but somehow similar functionality. Essentially, a logical address does not identify an actual or an existing address, however, it points to an abstract address that is located inside an abstract address space. On the contrary, a physical address is used in …

Question Two

This scheme has one major advantage which is characterized by effectiveness in the mechanism involved in data and code sharing. In this process, only a single copy of the compiler or an editor needs to be retained in the memory. Most importantly, all the processes that need to access the compiler code or the editor …

Question Three

The logical address has 16 bits.

The physical address has 15 bits.

Question Four

By definition, segment tables refer to a collection of base-limit registers. It, therefore, implies that segment can be shared in a situation where entries made to the segment table are meant to perform two different jobs and as such, they point to the same or one physical location. For this to happen, the shared segment number must be the same and there must be identical base pointers for the two processes involved. 

Question Five Internal fragmentation is referred to as the wasted space that is associated with rounding up of the real requested allocation within each allocated block due to the allocation granularity.  On the other hand, external fragmentation….