Skip to main content

Introduction To UNIX Operating System

  • What is UNIX?
UNIX is an operating system which was first developed in the 1960s. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops. UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows which provides an easy to use environment. However, knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available. First version of UNIX developed at the University of California Berkeley.

  • The UNIX Operating System

The UNIX operating system is made up of three parts: 

1. The kernel

2. The shell

3. Utilities 


THE KERNEL

• The kernel of UNIX is the hub of the operating system.

• It allocates time and memory to programs and handles the filestore and communications in response to system calls. 


THE SHELL

Shell is the command line interpreter. 

  • Shell is just another program 

A program or command which interacts with the kernel and it may be any of:

  • built-in shell command

  • interpreted script 

  • compiled object code file 

It searches the filestore for the file containing the program and then requests the kernel through system calls to execute the program.

When the process has finished running the shell then returns the UNIX prompt to the user indicating that it is waiting for further commands.

The shell acts as an interface between the user and the kernel.

When a user logs in, the login program checks the username and password, and then starts another program called the shell.

The shell is a command line interpreter (CLI).

It interprets the commands the user types in and arranges for them to be carried out. The commands are themselves programs.

When they terminate, the shell gives the user another prompt on our systems. 


UTILITIES

• UNIX provides several hundred utility programs, often referred to as commands.

• The commands accomplish universal functions such as printing, editing files, etc. . 


UNIX Operating System

If you are interested to know more on any other subject in which you are interested or if you have any doubts then tell us in comment about it.  

Comments

Post a Comment

Popular posts from this blog

8085 Microprocessor: De-multiplexing of AD0-AD7 Address and Data Lines

  De-multiplexing of AD0-AD7 of 8085 Microprocessor THE ADDRESS AND DATA BUSES: • 8085 Microprocessor have total 16 address lines and 8 data lines. • 8 signal lines A8 – A15 which are unidirectional. • The other 8 address bits are multiplexed with the 8 data bits. So, the bits AD0 – AD7 are bi-directional and serve as A0 – A7 (address bus) and D0 – D7 (data bus) at the same time. • During the execution of the instruction, these lines carry the address bits during the early part, then during the late parts of the execution, they carry the 8 data bits. In order to separate the address from the data, we can use a latch to save the value before the function of the bits changes. THE CONTROL AND STATUS SIGNALS: • There are 4 main control and status signals. 1. ALE (Address Latch Enable): This signal is a pulse that become 1 when the AD0 –AD7 lines have an address on them. It becomes 0 after that. This signal can be used to enable a latch to save the address bits from the AD lines. 2. RD (Rea
Post a Comment
Read more

Interrupts in 8085 Microprocessor: Vectored-Non Vectored Interrupts And Maskable-Non Maskable Interrupts

Vectored Interrupt: In vectored interrupts, the manufacturer fixes the address of the ISR to which the program control is to be transferred. the processor automatically branches to the specific address in response to an interrupt.  • The TRAP, RST 7.5, RST 6.5 and RST 5.5 are vectored interrupts. Non-Vectored Interrupt:   But in non-vectored interrupts the interrupted device should give the address of the interrupt service routine (ISR).    • The INTR is a non-vectored interrupt. Hence when a device interrupts through INTR, it has to supply the address of ISR after receiving interrupt acknowledge signal. Maskable & Non-Maskable Interrupt: The hardware vectored interrupts are classified into maskable and non-maskable interrupts.  • TRAP is non-maskable interrupt.  • RST 7.5, RST 6.5 and RST 5.5 are maskable interrupt. Masking is preventing the interrupt from disturbing the main program. When an interrupt is masked the processor will not accept the interrupt signal. The interrupts ca
Post a Comment
Read more

Interrupts in 8085 Microprocessor-Hardware Interrupt And Software Interrupt

What is Interrupt and how it is generated? Interrupt is a signal send by an external device to the processor, to the processor to perform a particular task or work. In the microprocessor based system the interrupts are used for data transfer between the peripheral and the microprocessor. When a peripheral is ready for data transfer, it interrupts the processor by sending an appropriate signal to the interrupt pin of the processor. If the processor accepts the interrupt then the processor suspends its current activity and executes an interrupt service subroutine to complete the data transfer between the peripheral and processor. After executing the interrupt service routine the processor resumes its current activity. This type of data transfer scheme is called interrupt driven data transfer scheme. Types Of Interrupt: The interrupts are classified into software interrupts and hardware interrupts. • The software interrupts are program instructions. While running a program, if a software
Post a Comment
Read more