Day 01Part 04- Operating sysytem for computer-Who executes the Program and where program is resides.

Day 01Part 04- Operating sysytem for computer-Who executes the Program and where program is resides.

Operating System for Computers – Day 01, Part 04

Who Executes the Program and Where Does the Program Reside?

 Introduction

A program is a set of instructions written to perform a specific task. To execute a program, the Operating System (OS) manages its loading, execution, and termination. But where does a program reside, and who executes it? Let’s break it down.

 Where Does a Program Reside?

1. Storage (Secondary Memory – Hard Disk, SSD, etc.)

Before execution, a program is stored in secondary memory (HDD, SSD, or external storage).
 Example: Applications like MS Word, Chrome, or a game are stored as files on the hard disk.

2. RAM (Primary Memory – Temporary Storage During Execution)

When a user runs a program, the OS loads it from secondary storage into RAM.
Why? Because RAM is much faster than a hard drive and provides quick access for the CPU.
 Example: When you open a browser, the program moves from disk to RAM.

3. CPU Cache (Temporary Fast Memory)

 Some frequently used instructions are stored in CPU Cache to speed up execution.
Why? Cache memory is faster than RAM and reduces the CPU’s waiting time.

 Who Executes the Program?

1. CPU (Central Processing Unit – The Brain of the Computer)

 The CPU fetches, decodes, and executes instructions of a program.
 The Control Unit (CU) directs the operation, while the Arithmetic Logic Unit (ALU) performs calculations.

2. Operating System’s Role in Execution

 The OS acts as a manager, handling:
Process scheduling – Decides which program runs and for how long.
Memory management – Allocates RAM to active programs.
Resource allocation – Assigns CPU, disk, and input/output devices.

 Step-by-Step Execution Process

User clicks to open a program (e.g., a browser).
The OS loads the program from storage into RAM.
CPU fetches and processes instructions from RAM.
Execution continues until the program is closed or task is completed.
The OS clears memory after execution to free up resources.

Conclusion

Programs reside in secondary storage (HDD/SSD) and move to RAM during execution.
The CPU executes the program with the help of the OS.
The OS plays a crucial role in managing memory, CPU scheduling, and execution.

 Want to learn more about process management or scheduling in OS? Let me know!

Day 01Part 04- Operating sysytem for computer-Who executes the Program and where program is resides.

iv semester cs3451-introduction to operating systems

Installation and Configuration of Operating System

UNIT-I Operating Systems Functions

Operating-System.pdf

Here’s a clear explanation for Operating System – Day 01, Part 04, covering who executes a program and where the program resides in a computer system:

Operating System Basics – Program Execution

Who Executes the Program?

The CPU (Central Processing Unit) is responsible for executing the program.

• It fetches, decodes, and executes instructions.

• The Operating System (OS) manages the CPU’s scheduling and decides which program gets to run next.

Where Does the Program Reside?

Programs initially reside on the hard disk or SSD, but to be executed, they must be loaded into main memory (RAM).

Steps:

1. Program stored on storage device (e.g., .exe file on HDD/SSD)

2. OS loads the program into RAM

3. CPU fetches instructions from RAM and begins execution

In Summary:

• Storage (HDD/SSD): Long-term location

• Main Memory (RAM): Temporary execution location

• CPU: Executes instructions one by one

• OS: Manages loading, memory, and execution control

Would you like a diagram of this flow, step-by-step execution example, or intro to process management?

Day 01Part 04- Operating sysytem for computer-Who executes the Program and where program is resides.

I UNIT – I- SCS1301- OPERATING SYSTEM