BACKING STORAGE UNITS- BACKING STORAGE UNITS NEED FOR HIGH CAPACITY...

4. Backing storage units

- Backing storage units need for high capacity data storage devices that can store

data in a more permanent form for later retrieral, updating and referencing.

- Backing storage is also called secondary storage external storage and auxiliary

storage.

Chapter 2: MICOPROCESSOR.

Question 1. Cache Memory?

- Cache memory is a small amount of very fast store with faster access time than

the main memory.

- Cache memory is used to temporaryty store data instructions that are likely to be

retrieved many times, thus speeds up the processing of data.

- Sits between main storage and the processor acting as holding area through which

all data and instructions pass.

- Old data in the cache memory is over written by new then cache is full.

Question 2. Virtual Memory?

- Virtual memory makes use of both the main memory and backing store.

- In a virtual memory sys, each user has the illusion that his program is in the main

memory all the time.

- The sys maintains this illusion by keeping some of the “unused” portion of the

program’s code and data on a backing store device which is usually magnetic disk

- The movement of the unused portion from the backing store to the mian memory

is transparent to the users.

- Please refer to diagram for virtual memory.

Backing Store Main Memory

A3

A2

A1

A3

A2

A1

Virtual Memory

Chapter 3: BATCH/ ONLINE AND REAL TIME PROCESSING SYSTEM.

Question 1. Batch Processing System?

- Def: Computer processing does not begin until all the input data has been

collected and grouped together called Batched Generally data is accumulated for a

certain period of time or unitl a certain quantity.

- Ads:

 Response time is not critical.

 Need to process large volumn of data.

 Computer efficiency is more important than response time.

- Dis:

 Time between recording and processing of source document is long

 Rereen normally required if errors are encountered.

 Data is not current.

 Error correction is more difficult.

Question 2. Online Processing System?

- Def: Inputs data enters the computer directly as soon as it is being transacted.

There information will be processed immediately and updated into the master file.

- Ads:

 Enter availability of information for decision making.

 More accurate data capture.

 Schedules suits user.

- Dis:

 CPU time is used less efficiently.

 Random arrival of transactions, terminal operator process each

transaction separately.

 More expensive than batch processing.

Question 3. Real Time Processing System?

- Def: One which controls the environment by receiving data processing them and

returning results sufficiently quickly to affect the functioning of the environment

at that time.

 Response time is very critical and sufficient quick.

 Expensive hardware & software.

 Very complex in terms of hardware & software.

Chapter 4: PRINTERS AND TERMINALS.

Question 1. Classification of printers?