computer system organisation notes

computer system organisation notes class 11

computer system organisation notes


Computer is an electronic device which can perform varieties of operation to perform (execute) a task.

Input device :-

input device receive symbols (input) from the the users and it converts into machine understandable form .
ex: keyboard , mouse , microphone.

Output device:-

It receive signals in machine form and it converts into human under stand-able form.
ex: monitor,printer,speaker


C.P.U     ->   Central process unit
it is also known as brain of the computer system as it govern all the operation which carried out in computer system it decide what to do, when to do and how to do.

parts of CPU(i) CU          (ii) ALU

CU(control unit):-

All the decisions and program including device management done by control units. it act as a manager which control variety of task for execution.

ALU(arithmetic  and  logical unit):-

 It is responsible for all the calculation required by the program.
  • cache
  • RAM
  •  ROM
  •  secondary
  • primary

 Cache memory:-

It is very high speed small memory used by the computer system to store recent programs which are executed.

                RAM                                                                   ROM

1. random access memory                                 1. Read Only Memory
2. data stored in RAM will get erased               2. data stored permanently
     automatically when power is off.
3. volatile memory                                             3. non volatile memory

secondary memory:-

It is used to store large amount of data permanently.
ex:- hard disc, CD,DVD,pen-drive,tape drive.

BRD–> Blue ray disk

     memory concept

1. 1 bits        –>   smallest unit
2. 4 bits        –>   1 nibble
3. 8 bits        –>   1 byte
4. 1024 byte –>   1 kilo byte (KB)
5. 1024 KB     –>   1 MB ( mega)
6. 1024 MB    –>   1 GB  (Giga)
7. 1024 GB     –>    1 TB  (tera)
8. 1024 TB      –>    1 PB  (peta)


set of programs that governs the operation of the computer system and make the hardware run.
system software:-the software that controls internal computer operation is called system software.

operating system:-

it is the program which acts as a interface between user and computer.
ex.- windows,Linux

function of operating system:-

(1) it provide interface between user and hardware .
(2) its loads necessary program in memory for execution.
(3) it is responsible for memory management,device management and input,output.

types of operating system:-

(1) single user operating system:-

  only one user program can be executed at a time. ex- DOS

(2) multi user(OS):-

it can execute more than one users program  simuntationaly.
ex: windows server, Linux

(3) time sharing:-

each users program allotted a fair CPU time for their program execution.

(4) real time(OS):-

it is mainly used in scientific calculation and associated project . the task must be executed in stipulated time.

(5) multi processing(OS):-

its supports more than one processor (CPU) and it is capable of load sharing. first CPU is known as master and other CPUs refereed as slave.
windows sever, Linux.

language processor:-

 it converts high level language into machine language.

(i) assembler:-

 it converts assembly language program into machine language . it is mainly used in hardware programming.

       compiler                                                                       Interpreter

1. it convert high language program               1. it converts high level language
into machine language in ”one go”.                          program into machine language
2 . compiler should not be present in                    2. it must be present in the memory all
memory all the time .                                                   the time during program.
3. compiler execute the program only           3. interpreter execute the lines in sequence
 when whole program is error free.                     which are error free and stop execution
                                                                                            when error found in a line.
4. ex- C++, JAVA                                                         4. ex- visual basic , JAVA
     visual C++, python

system utilities:-

system utilities are small program designed to managed compute peripheral.
ex. text radiator,backup utilities,compression utilities disk defragmenter and antivirus software.

application software:-

these software are designed to carried out operation for a specific application.these software runs under operating system.

general purpose software:-

these software program are designed to perform generalized task.
ex- ms word,ms excel,ms power point,photo shop.

customized software:-

these software are created as per customer requirement.
ex.-invoice management,railway reservation,banking system,student information system,hotel management system.


software libraries are set of predefined code which are available to programmer for use in development of new code.
computer system organisation notes