Operating System – Grade XI

Operating System is a system software that manages computer software and hardware resources and provides platform to run computer software.

Address Bus: Address Bus is a group of wires or lines that are used to transfer the address of memory or input ,output devices. It is unidirectional and can transfer maximum of 16 bits address which means it can address 65536 different memory location.

Data Bus: Data Bus is used to transfer data within microprocessor and memory or input output devices. It is bidirectional as microprocessor requires sending and receiving data. It can transfer 8 bit of data.

Control Bus: A Control bus is a computer bus used by the CPU to communicate with devices that are contained within the computer. CPU transmits control signal to components & devices to transmit control signals to control bus. One of the main objective of a bus is to minimize the lines that are needed for communication.

Cache Memory: Those memory in which frequently used data and instruction are stored in cache memory. CPU cache is more complicated than other kinds of caches. And thus is divided in two parts:

  1. L1 Cache
  2. L2 Cache

L1 Cache is same kind of memory which is built into the same CPU and the place where the CPU first try to access.

L2 Cache is built on the same ways the L1 cache into the CPU but sometimes it can also be located in another chip or in a MCP (multi chip package module). It can also be a complete separate chip.

The difference is in size. This way the data is easier to be found in the L1 than L2. Making the access much faster , if the data is not found in L1 then the data is looked in the bigger L2 cache.

Secondary Memory

Secondary memory is the memory where program and data are stored for future use but cannot be accessed by processor directly. When computer wants to use the stored data , they are first copied into primary memory. Secondary storage devices have greater storage capacity. These memory are non-volatile in nature. Example hard disk , pendrive etc.

Types of secondary memory:

  1. Magnetic Memory
  2. Optical Memory

1. Magentic Memory

A. Magnetic Tape:

I. It is used in cassett.
II. It has larger storage capacity and data are stored in sequential order.
III. It is less expensive.
IV. It is slow to use.

B. Hard Disk:

It is non-volatile storage device that stores digitally encoded data at rapidly rotating platters with magnetic surface. Hard disk allows random access to data storage capacity of it ranges from 20 GB to TB. HDD have greater storage capacity and is more durable and reliable.

2. Optical Disk

It is an electronic data storage medium that can read and write using a low power laser beam. It is flat and circular plastic or glass disk on which data are stored in the form of light and dark pits.

  1. CD ROM: It is a compact disk that contains data accessible to but cannot be writable by a  computer. A laser beam is shown on a reflective surface of disk to read the content. CD ROM are recorded that cannot be erased or be erased or filled with new data. CD ROM are popularly used for sharing software , games , multimedia . The most common size of CD ROM disk is 120 mm in diameter and 1.2 mm thick and can store up to 650 MB an standard of 74 minutes.
  2. DVD( Digital Versatile Disk): it is a high density compact disk , popular optical disk used i describing  3 ways of data storing. They are:
    a. DVD-ROM: It has a data which can be read but cannot be written.
    b. DVD-R: DVD R can be written on your own
    c. DVD-RW: It can be written and read as many times as user wants.
    It’s main uses are for software , movies , application etc. distribution. DVD are of same dimension of CD’s but it can store 6 times more than CD 1X of CD writing. Speed is equal to 153 KB. Each DVD can store 4.7 GB of compressed data.


Printer are the next commonly used output device. Human readable output is produced by using printers. the output may be text pictures etc. on paper. Printed output is usually refereed to as hard copy output and don not require the electric power to rad. Printers can be classified according to what they print once they are:

  1. Character Printer, that prints one line of the text at a time.
  2. Line Printer, thtat prints a page  at a time.

According to the consideration while manufacturing there are two types of printer:

  1. Impact Printers: They uses mechanical mechanism that uses hammer or pins to strike against a inked ribbon on paper to print the text. Example: dot matrix, daisy wheel printer etc.
  2. Non Impact Printer:  They do not use such mechanical mechanisms for printing but they use thermal, laser beam , chemical etc. technology for printing. Example laser printer , inkjet printer. Impact printers can produce multiple copies f a print at a time whereas copies.

Also Read: Differentiate between Impact Printer and Non-Impact Printer. (Grade 11)


Peripherals are devices that are attached to a computer system to enhance it’s capabilities. It includes input devices,output devices and communication devices.

  1. Serial Port:  Serial port is a serial communication , physical interface through which information transfers in or out one bit at a time. They are still used in various peripheral devices because they are simple , cheap etc. It consists of 9 pins.
  2. Parallel Port:  Parallel port is a type of interface found on computer  for connecting various peripheral s . It consists of 25 pins and used in devices like web cameras , external HDD’s and CD-ROM drives.
  3. USB port: Universal serial bus (USB) is a network type of serial connection that is much faster old serial ports. Many devices like keyboard , mouse , printer, etc uses USB port.
  4. Fire wire or IEEE 1394: It is a high speed interface that was developed by apple computer.




%d bloggers like this: