Program vs Process (low level concepts)

Summary

The video script from 'Program is not a Process by Core Dumped' explores the nuances between a program and a process in computing. It explains that a program is a passive sequence of instructions stored on disk, while a process is an active, temporary instance of a program running in memory. The script delves into early computing history, the evolution of batch systems to time-sharing operating systems, and the concept of concurrency. It also discusses the memory layout of processes, including text, data, stack, and heap sections, and touches on the differences in how compiled and interpreted languages like C, Java, and Python are executed.

Takeaways

• 🖥️ Programs vs Processes: A program is a sequence of instructions stored on disk, while a process is an instance of a program running in memory, with its own allocated resources.
• 🧠 A process is active: Programs are passive entities stored on disk, but when they are executed, they become active entities known as processes.
• 💾 Memory allocation: Processes have distinct memory regions for instructions (text section), global variables (data section), and temporary data (stack and heap).
• 🔀 Single core concurrency: Early home computers popularized concurrency, where a single-core CPU switches between multiple processes to simulate multitasking.
• 📝 Compilation in C: In compiled languages like C, the program is converted into CPU instructions and saved to an executable file with data and instructions stored separately.
• 🐍 Interpreted languages: In Python and JavaScript, there is no compilation into machine code; instead, the interpreter executes the code at runtime, making them distinct from compiled languages like C.
• 📚 Interpreter process: In Python, when the interpreter runs, it loads the Python code into memory as data, while the interpreter itself becomes the active program (process).
• 📝 Text vs Data regions: The text section in memory remains constant for the duration of the process, while the data section may change based on runtime actions.
• 🔁 Recursive functions and memory: Stack memory, often limited, is used for function calls, and recursive functions can lead to stack overflows if too many layers are created.
• ⚙️ Separate processes, shared programs: The same program can run as multiple processes simultaneously, each having its own memory space but the same set of instructions (text section).

Q & A

What is the main difference between a program and a process?

A program is a passive entity, typically an executable file stored on disk, while a process is an active entity that is created when the program is loaded into memory and executed. A process has its own memory space, including text, data, stack, and heap sections.

How does the memory layout of a process differ from that of a program?

The memory layout of a process includes the text section (which holds executable code), the data section (holding global variables and constants), the stack (for function calls and local variables), and the heap (for dynamic memory allocation). A program is simply a file, while a process is a live execution with allocated memory.

What is the significance of the text section in a process?

The text section contains the executable code of the program. It is a part of the process’s memory that remains constant in size and content throughout the execution of the process.

Why is recursion sometimes discouraged in programming, according to the transcript?

Recursion can be discouraged because recursive functions use the stack for each function call, which can lead to stack overflow if the recursion depth is too high. Stack memory is limited, and exceeding it can crash the program.

What is the role of the heap in a process's memory layout?

The heap is used for dynamic memory allocation during a process’s runtime. Memory from the heap is allocated and freed as needed, and the size of the heap can grow and shrink during the execution of the program.

How do interpreted languages like Python handle the difference between a program and a process?

In interpreted languages like Python, the source code is not directly executed by the CPU. Instead, the Python interpreter (itself a program) is executed, and the source code is loaded into one of the interpreter’s memory sections (typically the heap) as data to be interpreted.

Why is it important to distinguish between a program and a process in computing?

Distinguishing between a program and a process is important because a program is simply a file that can be executed, while a process is the running instance of the program with its own memory and resources. Multiple processes can run from the same program, but they operate independently.

How does Python handle global variables and string literals after compilation?

After compilation in Python, global variables and string literals are stored in the data region of the process. They are separated from the CPU instructions and can be accessed during runtime without being part of the executable code itself.

What is concurrency, and how does it relate to early computer systems?

Concurrency refers to the ability of a system to execute multiple processes or tasks at the same time, allowing for time-sharing. In early computer systems, this concept was introduced to allow multiple users or tasks to share the CPU's resources. Concurrency became popular with home computers, allowing single users to run multiple programs at once, even on single-core CPUs.

What happens when a Java program runs, according to the script?

When a Java program runs, it is executed within the Java Virtual Machine (JVM). Java code is compiled into bytecode, which is then interpreted or just-in-time compiled by the JVM. Each Java process typically runs with its own instance of the JVM.

Outlines

00:00

🖥️ Introduction to Programs and Processes

The narrator expresses their interest in a YouTube channel that delves into technical computer science concepts. The discussion opens with a question about the difference between a program and a process. The narrator offers an initial explanation, stating that a program is stored on disk and is static, while a process is in memory and more temporary. Early computer systems ran jobs in batch mode, but with the rise of time-sharing, user programs were executed concurrently, allowing multiple processes to run simultaneously. This leads to a deeper examination of the distinction between programs and processes.

05:01

💡 Concurrency and Memory Allocation

The video explores how early home computers popularized concurrency, even with single-core CPUs. The narrator speculates that concurrency refers to multiple processes running at the same time with the CPU context-switching between them. They dive into the difference between programs and processes, pointing out that a program is a set of instructions, while a process is an active instance of those instructions. The narrator begins contemplating how the memory sections of programs, such as global variables and stack memory, function once a program is compiled into executable code.

10:01

📂 Memory Layout and Processes

The narrator dives deeper into how programs interact with memory when they become processes. They explain that when a program is loaded into memory, it is divided into sections like the 'text section' for code and 'data section' for variables. While the text section remains unchanged, the data section can vary based on the program’s runtime behavior. The concept of memory allocation is discussed in terms of recursive functions and variable memory needs, explaining how a process uses memory differently than a static program.

15:02

🔍 Understanding Processes with Examples

The video provides a practical example of processes using a text editor. Opening two files in separate windows results in two different processes, even though the program is the same. The narrator highlights that each process has its own memory space, though the code (text section) is the same. They further explain that processes are an operating system-level concept, each with its own ID and memory management. While the video doesn’t go too deep into technical details, it emphasizes that a process is more than just an active program—it’s a complex entity managed by the OS.

💾 Interpreted Languages and Processes

The narrator discusses how interpreted languages like Python and JavaScript differ from compiled languages like C. Unlike compiled languages, which turn source code into executable files, interpreted languages run through an interpreter. Each time a Python program runs, a process is created, and the interpreter reads the source code. The narrator brings up an interesting point about how even though Python has a compilation step to bytecode, it's often overlooked due to its runtime nature. The interpreter manages both the text and data sections for these interpreted programs.

Keywords

💡Program

A program is defined as a passive entity, a set of instructions stored on a disk waiting to be executed. In the video, the speaker differentiates a program from a process, stating that a program resides in storage and needs to be loaded into memory to run. For example, the text editor application is referred to as a program before it's executed.

💡Process

A process is an active entity, which is a program in execution. The video explains that a process has its own memory layout and resources when running. For example, when two files are opened using the same text editor, each file runs as a separate process even though the program is the same.

💡Memory layout

Memory layout refers to how the memory is structured when a process runs, with different sections like the text, data, stack, and heap. The text section contains the executable code, and the data section contains variables and constants. The video discusses how memory is allocated for processes and varies in size based on what the program is doing.

💡Text section

The text section is the part of a process’s memory layout that holds the executable code. In the video, it is mentioned that this section never changes during execution, unlike other sections like the stack or heap. This is a core part of the process and differentiates the code from data and runtime memory.

💡Data section

The data section stores global variables and constant values used by a process. In the video, the speaker points out that this section can change in content, depending on what the program is doing, but not in size. It holds important information, like global variables in compiled C programs, as part of a process's memory.

💡Heap

The heap is a section of memory allocated for dynamic memory use during program execution. The video emphasizes that the heap grows and shrinks as needed, and it stores large or dynamically created data. The heap is used by the process to manage memory for things like variables created at runtime, such as a text file in a text editor.

💡Stack

The stack is another memory section used by a process, mainly for managing function calls and local variables. In the video, the stack is described as limited in size and used to store temporary data like local variables or manage function calls, including recursive functions. It grows and shrinks as functions are called and completed.

💡Concurrency

Concurrency refers to the ability to run multiple processes or threads simultaneously, or seemingly so by time-sharing CPU resources. The video touches on the history of concurrency, explaining how early computers and time-sharing systems introduced this concept to allow multiple programs to run at once. This is distinct from modern multi-core processors.

💡Interpreter

An interpreter is a program that directly executes instructions written in a high-level programming language. The video uses Python as an example of an interpreted language, where the Python interpreter runs the code. Unlike compiled languages, where the entire program is converted into machine code, an interpreter executes code line-by-line.

💡Compilation

Compilation is the process of converting source code written in a high-level language into machine code that can be executed by the CPU. The video contrasts compiled languages like C, where a separate compilation step creates an executable file, with interpreted languages like Python, which are executed directly by an interpreter after being converted to byte code.

Highlights

The distinction between a program and a process: a program is a passive entity stored on disk, while a process is an active entity in memory.

Concurrency in early computers allowed a single user to run multiple programs simultaneously, even with a single-core CPU, using context switching.

In computer science, programs are referred to as processes when executed, not programs.

The text section of memory stores executable code, while global variables and constant values are stored in the data section.

Heap and stack memory regions complement the data section for runtime memory allocation, such as user inputs and temporary variables.

The stack is used for local variables and function calls, while the heap is for dynamically allocated memory.

The stack has limited memory, which is why stack overflows can occur, especially in recursive functions.

The text section of a process's memory never changes in size or content during execution, but the data section's contents may vary.

In interpreted languages like Python, the interpreter itself is a process, while the Python source code is treated as data for the interpreter.

Global variables and string literals in a compiled C program are saved in the data region, while local variables go to the stack.

The difference between compiled and interpreted languages: in Python, source code is not executable by itself but is processed by the interpreter.

Processes associated with the same program, such as opening two text files in the same editor, operate in separate memory spaces.

Java programs are run by the Java Virtual Machine (JVM), which operates as a separate process to execute Java bytecode.

Even though Python source files are text, they are compiled to bytecode before execution by the interpreter for performance optimization.

Recursion, while theoretically valid, is discouraged because of memory limitations in the stack, which can lead to stack overflow.

Transcripts

program is not a process by core dumped

probably my new favorite YouTube channel

because it takes me back to the days

when I was just getting a computer

science degree and I was actually

learning about things that were

interesting most people learn to code so

they can actually build things that are

genuinely useful not me I just like

understanding how things work and this

channel is going to let us do that a

question that arises in computer science

is what to call all the activities

performed by the CPU I hate to pause it

right now but I think so just based on

the title The first thing that I think

of is that a program versus a process

what's the difference um I guess a

process is just an instance of a program

for example like for one program you can

have multiple processes and a program I

believe is just going to be stored on

your dis so it's like persisted there

versus a process is going to be stored

in memory and it's going to be

shortlived or temporary at the very

least early computers were batch systems

that executed work units called jobs

as I discussed in my video about

concurrency when time sharing operating

systems emerged they were designed to

share the CPU among multiple users so it

was said that those systems ran user

programs interesting I actually don't

know very much at all about very early

computers eventually the home computer

Market popularized the use of

concurrency to allow a single user to

run multiple programs at once that's

very interesting actually let me replay

that did he say concurrency eventually

the home computer Market popularized the

use of concurrency the use of concurr

currency what he means by that I think

is not like this is like the invention

of a multi-threaded or like multi-core

CPU it's more that just you have

multiple processes running at the same

time and then the CPU is going to

contact switch between them uh that's

very interesting so that was probably

even with a single core CPU to allow a

single user to run multiple programs at

once but in computer science we don't

refer to these entities as programs but

rather as

processes so today we are going to learn

the difference that's very interesting

to this shows me how much I actually

don't know because I thought Linux is

just I I believe from its birth was

using like processes so that's

interesting it's kind of hard to believe

that there was a point you literally

couldn't run multiple processes at the

same time just imagine living like that

today I don't even think it's possible

Concepts hi friends my name is George

and this is core dumped for the vast

majority the answer to this question

seems obvious programs after all that's

what CPU does right it runs programs but

as I mentioned before in computer

science the correct term is process

that's technically correct I wonder how

mad people would get though if you just

said program kind of reminds me of the

other day how I said pointer in

technically the wrong context informally

a process is usually defined as a

program in execution even though this

definition is technically correct what I

find frustrating is that it is not

enough to help a casual reader

understand what a process is

so let's start by establishing what a

process is not think about this

interesting I think he's right CU like

the devil is in the detail to say that a

process is an instance of a program

isn't really getting into the hardware

and like like I said kind of at the

beginning the hardware matters like the

dis versus like the memory where each is

stored and how it's run and all that

different programs are obviously

intended for different purposes but in

many respects they are similar when

executing as they all reduce to the

fundamental actions performed by the CPU

and here's where we can start making

distinctions a program is a sequence of

instructions and the data that the CPU

needs to accomplish a specific

task now if you carefully Analyze This

description you'll notice that it can

also describe an executable file and

that's because that's pretty much what a

program is let's say like you have a c

program you compile it it turns into

like CPU instructions that the CPU is

going to load into memory and execute

that makes sense so what is this data at

the top of my head I actually don't know

cuz the executable file it has data

itself what does that mean cuz I know

when a process is running it's going to

have some memory allocated like the

stack space Etc but the executable file

itself has data I'm curious about that

so I wanted to at least have like a

little bit of understanding of what that

meant so I just went to chat gbt and

asked it so can you give me a simple

example of a c program after compilation

what parts of it would be the CPU

instructions and which parts of it would

be the data I think that the CPU

instructions are like Rel relatively

straightforward in terms of like if you

had conditional statements loops and

things like that like the control flow

that makes sense that those would turn

into CPU instructions but I was

surprised to see that so if you have

like Global variables and for example

string literals those are actually saved

in the data region after the program is

compiled and so local variables like

this are going to be as we would kind of

expect pushed onto like the stack space

and I would assume like the same thing

with recursive calls of course but it's

interesting to me that a string literal

like this would be saved not as like a

CPU instruction but rather in the data

region so what does that mean like if I

had multiple print statements would that

same string be copied multiple times I'm

assuming not CU that sort of

optimization could be made but actually

now that I think of it on second thought

if there are distinct strings and you

want to update one of the strings you

don't necessarily want both strings to

be updated I think if we were to dig

deeper into this we would probably be

getting really into the realm of like

operating system so I guess I won't do

that right now but it does make sense

that a lot of variables and just large

amounts of data are going to be stored

in the data region of an executable file

separate from the code instructions and

so all of that is going to be loaded

into memory when it's actually run but

there's going to be separate memory

regions like the stack and probably the

Heap that can complement the data

section a program is that passive entity

that resides in your storage waiting for

you to click on it to tell the the

computer to start running

it as I've mentioned many times in the

past to run a program it first needs to

be loaded into memory as that's where

the CPU can start fetching instructions

and

data when loaded into memory the section

containing the executable code is known

as the text section while data such as

Global variables and constant values is

loaded into the data section okay I mean

he literally just answered the question

sorry about that but running a program

requires more than these two sections it

also need extra space in memory to store

all the data generated at runtime like

user input and temporary results or

variables yeah so he said at runtime

like there's going to be separate memory

so I don't think he's probably going to

have enough time to like go into the

details of every little thing in this

video but I'll try to add like my

commentary which is that so conceptually

think about it for a second why would we

not have the memory up front for

something like a recursive function or

even different variables that may or may

not necessarily be allocated why do we

need like a variable amount of memory

because you don't necessarily know you

could have a recursive function

depending on the input to the program it

might stack up 10 times before hitting

the base case or depending on a second

input it might stack up 20 times if you

pre-allocate the memory you don't

necessarily know how much memory it's

going to take now even the stack is

technically Limited in memory that's why

like stack Overflow occurs like this

region called the stack which recursive

functions use it will hit a limit like

there is a limit to this I think you can

sometimes update that limit many

languages will have like a default limit

size but anyways we already know a lot

about the stack and the Heap such as the

fact that they are growing and shrinking

in size all the

time the tech section is the only one

that never change neither in size nor

content interesting that would make

sense based on like the CPU instructions

text is not going to change stack is

obviously growing for reasons I talked

about not just for recursive functions

but also like one function calls another

it's going to go on the stack when that

function finished it's going to return

back to the previous function the Heap I

actually don't remember off the top of

my head but I'm pretty sure one program

if it's using Heap memory the amount of

memory that that program is actually

using from the Heap could change but

theoretically you should be able to use

as much memory as your computer has uh

for the Heap let me actually just double

check that just from our cursory Google

search I guess this part is actually AI

generated but it does look like a

program can use unlimited amounts of

Heap memory what's the default stack

memory limit in C for example um it

looks like it's 1 Megabyte I don't know

if that depends on the compiler but

again like you can see that this is like

relatively small so it's reasonable that

you could hit a stack Overflow even if

there's not infinite recursion like

that's why recursion is actually not

good and you're hearing this from me the

data structures guy on YouTube that

generally speaking you don't want to do

recursion even for valid recursion you

could hit the memory limit anyways but

we can't say the same about the data

section because even though it doesn't

change in size its content may varies

depending on what the running program is

doing as you can see so the data region

can vary in size I mean if this is part

of the executable I wonder if that means

that at runtime that that is like the

amount of memory that's being used by

that data region is going to change but

like all that memory should be allocated

for the programmer maybe I'm

misunderstanding let me just replay it

just in case can't say the same about

the data section because even though it

doesn't change in size its content may

varies depending on what the running

program is

doing as you can see even though

initially we loaded the program into

memory when running this layout can no

longer be considered as a program of

course not it has now become a

process and please note that this is the

memory layout of the process not the

process

itself the reason this definition is

often con that's interesting so that's

the memory layout of the process but not

the process itself so how do you define

a process in my head it's an operating

system level unit right like the

operating system is managing the process

it gives it an ID if there are multiple

threads that are a part of that process

they will possibly share memory I guess

we're getting overly technical let's

just continue considered informal is

that the notion of what a process is is

far too complex to be captured in just a

few words we're not going to go into

technical details in this video because

there's a video about processes already

scheduled but for now let me help you

get an idea of what a process

is consider that little program that

comes with your operating system to open

text

files now imagine we have two files to

read if we open both files the operating

system will launch the text editor app

twice this results in two separate

Windows each displaying a different text

file both are the same program but two

completely different processes

right each process has its own memory

space of course while the content of the

text section in both processes memory is

identical since they are the same

program the data they are working with

is different right so that obviously

makes sense and it also makes sense that

in a text editor all of the data would

be going to the Heap you again wouldn't

want to run out of like stack space for

that imagine just declaring a massive

variable with megabytes like a megabyte

long string or something like that

probably want to avoid something like

that in this example the first process

is working with a much larger text file

than the second so it naturally requires

more memory to manage its

data and if you're a casual viewer

hopefully that's everything you needed

to understand the difference between a

program and a

process I are we casual viewers I don't

feel like I'm a casual viewer I always

want to know like the exact details and

by the way definitely subscribe to this

guy if you're not convinced by now

definitely subscribe to this guy Cor

dumped I don't want to just call him

this guy I actually know him very little

uh he's very nice guy he's actually

perfectly okay with me reacting to this

video I probably should have mentioned

that towards the beginning but his

channel is just fantastic I could not

get enough of it I want to send a

special thanks to all of you because we

finally surpassed 100,000 subscribers I

enjoy learning new things as much as you

do in the same way I encourage you to

check out brilliant if you're going to

get brilliant definitely go to cump's

channel and use the link in his

description and make sure to support him

I emphasize that a program by itself is

not a process a program is a passive

entity whereas in contrast a process is

an active entity although two processes

may be associated with the same program

they are nevertheless considered two

separate execution

sequences I know that having a notion of

what a process is is not the same as

being able to Define it in technical

terms but as I mentioned earlier a

dedicated video on processes is coming

soon this episode is not over though

everything I've discussed so far makes

sense for compil languages when using

languages like C or rust the result of

the compilation is an executable file

that is the program itself but what

about interpreted languages like python

or JavaScript where there is no

compilation

process in Python for example every time

we want to run code we must first

instruct the computer to run The

Interpreter and then one thing I

actually want to go back to is he put

Java in the same realm as interpreted

and so that to me actually does make

sense given that like when you're

running a piece of java code is it the

code that's being executed because for

people who don't know Java turns into

like bik code and then there's a

separate program called the Java virtual

machine which then runs that Java code

so in a sense I think it is interpreted

it really is because what's running is

the Java virtual machine at least an

instance of it I'm actually not an

expert on Java if somebody wants to

comment maybe we can answer this

ourselves let's use Claude this time and

so I asked when a get away when a Java

process is running does it get its own

instance of the Java virtual machine yes

when a Java process is running it

typically does so this may or may not be

correct I'm going to assume it is

because for something basic as this I

would think Claude is correct we could

also Google this but so that's very

interesting so in that sense yeah I mean

Java definitely does feel like a

interpreted language I don't want to

start a debate or anything and in the

same realm I actually recently learned

this that python is also compiled like

there is a compil step like I used to

think like I had a very naive

understanding of how the python

interpreter worked I thought it

literally just read the python text

files line by line but there is a

compilation step so what is the

compilation step with python code and

how does it differ from java compilation

okay so there is a compilation step in

Python it's compiled into bite code but

it happens at runtime I believe there's

not an actual separate compilation step

so that honestly makes me feel like you

could not know that you could not know

that there's a compilation step in Java

just like you could ignore like the just

in time compilation with JavaScript and

you'd probably be fine I'm assuming this

is mainly done for optimization reasons

was there a point where python did not

have a compilation step why does it

exist or performance so it sounds like

it always was there and mainly does EX

for performance reasons or JavaScript

where there is no compilation

process in Python for example every time

we want to run code we must first

instruct the computer to run The

Interpreter and then tell The

Interpreter to execute our

code right so every time we run a python

file or Python program we're creating a

process and that process encapsulates

the python interpreter and it's going to

specifically be using the file itself

self as like the executable as the

instruction set not the instruction set

as the

instructions in other words there are

now two passive entities involved the

python interpreter which is a program

okay right so there's a separate unit

running for that process not just the

CPU reading like the lowle instructions

there are higher level instructions

involved file which is practically a

text file I would like to highlight here

the fact that the python source file is

not a program remember that source code

is just text that computers cannot

understand and therefore cannot execute

I guess in this case and maybe I'm

getting overly technical but even let's

say you took that python file and it

turns into bite code the distinction

between This and like that c program

example we were looking at towards the

beginning is I wonder if this python

when it's compiled into the bite code in

the bite code I wonder if there's a

separate region for the data versus like

the instructions I mean I wonder if that

matters at all but that's just something

that came to my mind so in this kind of

situations the program we're actually

asking the computer to run is The

Interpreter not the python code we

wrote once this new process is created

it has its own memory region with text

and data sections right I mean of course

every process has a text and data

section but I wonder how that relates to

like the bik code or like how like the

Java virtual machine does it this is

from the operating systems perspective

but from the python interpretor

perspective it's going to be reading

like the bik code where's the bik code

probably within the text

I think I'm just confusing myself maybe

they are distinct as well as a stack and

a heap just like any other

process the key Point here is that

what's loaded into the text section is

not our python source code but the

executable code of The Interpreter our

source code is loaded by The Interpreter

process into one of its data sections

most likely the Heap because it serves

as the data The Interpreter will work

right that's very interesting so this is

the program that's running for it to

know how to execute it's going to keep

fetching the data from the Heap that's

very interesting because still when a

program is running it's not just running

from top to bottom like there's control

flow for example like you might have

some instructions but if the if

statement does not evaluate to true that

if statement is going to be skipped that

must mean when you have a python

interpreter it's going to go through the

memory it's sure it can read through the

memory but like that itself needs to be

coded to skip certain parts of the code

so it's almost like when you're creating

an interpreter in a sense you're kind of

creating like an abstraction for like a

CPU work with to read and

interpret and let's wrap it up for now

compilers and interpreters deserve their

own videos since I'm committed to

continue releasing quality content once

again I encourage you to subscribe I

encourage you guys to subscribe as well

honestly his channel is fantastic