Ravi Bhuvan

Posted on Jul 22

OS Concepts and terms

Firmware

Permanently stored software on the hardware Device. give low-level control for specific hardware.

BIOS

Basic input-output system, its a low level firmware that embedded on the motherboard. it is responsible for booting up the system using 16-bit real.

UEFI

bios is old, Unified Extensible Interface is a replacement of traditional bios. which has a faster booting time as it can run in both 32 and 64-bit mode.

Important Terms

Compiler

A program that converts the high-level language(C++,java) into binary code(0s or 1s) so, that the computer can understand.

Loader

part of OS that loads and executes the file in the disk into memory, so PC can run.

Assembler

programs that converts low-level language to binary instructions(machine code)

Interpreter

Program that translates the code and runs line by line.(unlike compiler which translates the whole code first and runs)

System Calls

it is a way of programs that request services from OS kernel, like open()

#include <unistd.h>

int main() {
    const char *message = "Hello, World\n";
    write(1, message, 13);  //here write() is a system call
    return 0;
}

API (Application Programing Interface)

it is a set of rules/protocols that needs to be followed by the program, where two different software interact/communicate with each other.

Kernel

it is the core of an OS, which controls all the hardware

Shell

its a program the helps the user to interact with the kernel via commands

JVM (Java Virtual Machine)

it is VM which acts as a bridge between compiled java code and the OS. that's why java is referred as Compile Once, Run Anywhere.

Booting

the process of starting and loading the OS into the main memory.

Multi -

difference between multiprogramming and multitasking is

in multitasking - programs running simultaneously
in multiprogramming - programs are either ready or waiting for their turn.

Process vs Program

Program -
set of instruction which is yet to be executed. Its is a passive entity that stays in the secondary, which is content of the disks

single user can execute multiple programs
it is a file that needs to be executed
single program can be linked to multiple processes

Process -
active instance of a program.

it is an active entity which is running in the main memory
remains for a specific time
dynamic entity
sequence of execution of instructions

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