Hardware & OS

# Hardware & Operating Systems

Week 8

---

## Review

![](https://media2.giphy.com/media/v1.Y2lkPTc5MGI3NjExeTFqNTYyc2s5MjExdm02ODNsaWl5aGw1a2tjZGN6ajh1cjBldm9iYiZlcD12MV9naWZzX3NlYXJjaCZjdD1n/vr9CseLC85kdjC56lR/200.webp)

What are "semantics?"

The meaning we convey with language

What is "syntax?"

Words, character, grammar

What is a function?

A reusable section of code

After _defining_ a function, how do you _use_ it?

_Call_ the function

```py
do_something()
```

What is a parameter?

A named input that a function receives

What does the `return` statement do?

Ends the function and sends a value back to the caller

What is wrong with this code?

```py
def say_hello(name)
    print(f"Hello, {name}!")
```

Missing `:`

What is wrong with this code?

```py
def say_hello(name):
    print(f"Hello, {name}!")
```

The function body must be indented

What is wrong with this code?

```py
def echo():
    print(f'Your message was "{message}"')

print( input("Enter a message: ") )
```

Parameter not defined

What is wrong with this code?

```py
def square(x):
    y = x * x

print( square(8) )
```

Missing return statement

What is wrong with this code?

```py
def add(x, y):
    return x + y

print( add(5) )
```

The function needs two arguments, but only one was given

---

## Hardware

Hardware is the physical parts

Software is the programs that run on them

NOTE: Week 2 definition. Today is the parts. Week 6 was the inside of the CPU.

Each part does one of the four roles

- Input 
- Storage 
- Processing 
- Output

Inside a desktop

![Opened desktop computer](https://upload.wikimedia.org/wikipedia/commons/thumb/2/25/Computer_motherboard_6.jpg/960px-Computer_motherboard_6.jpg)

NOTE: The green board is the motherboard. The silver box at the top left is the power supply: it turns wall power into the voltages the parts need. The ribbon and colored wires carry data and power.

The **motherboard** connects the parts

CPU, memory, and storage plug into it

NOTE: Week 6: a circuit board, also called a PCB. The copper lines are traces. A phone's board does the same job, packed tighter.

**CPU** — processing

The chip that follows instructions

A 3 GHz CPU takes about 3 billion steps each second

NOTE: Central Processing Unit. Week 6: the ALU inside it does the math, built from logic gates. GHz is the clock speed. One core does one thing at a time. A multi-core CPU has several cores.

**RAM** — the CPU's workspace

Fast 🐇

Forgotten when the power goes off

![DDR4 RAM stick](https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/DDR4_DIMM_4GB_-2133_IMGP5813_smial_wp.jpg/960px-DDR4_DIMM_4GB_-2133_IMGP5813_smial_wp.jpg)

NOTE: Random Access Memory. Volatile storage. The program you are running, and the data it is using right now, live here. DDR5 (2020) moves about 50 GB per second. DDR1 (1998) was about 1.6 GB/s.

**Storage** keeps data after shutdown

Persistent

Slower 🐢 and cheaper 💲 than RAM

NOTE: A saved file lives here. Unsaved work is only in RAM, so a power outage throws it away.

**HDD** — spinning magnetic disks

![Opened hard disk drive](https://upload.wikimedia.org/wikipedia/commons/thumb/3/38/Seagate_ST33232A_hard_disk_inner_view.jpg/960px-Seagate_ST33232A_hard_disk_inner_view.jpg)

NOTE: Hard disk drive. A head floats over the platter and reads magnetic spots. About 300 MB/s. Older persistent storage: floppy disks (magnetic, about 500 KB/s) and optical discs (CD, DVD, Blu-ray; a laser reads pits, Blu-ray about 72 MB/s).

**SSD** — no moving parts

Stores bits as electrical charge

![Samsung SSD](https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Samsung_980_PRO_PCIe_4.0_NVMe_SSD_1TB-top_PNr%C2%B00915.jpg/960px-Samsung_980_PRO_PCIe_4.0_NVMe_SSD_1TB-top_PNr%C2%B00915.jpg)

NOTE: Solid state drive. About 5000 MB/s, which is why new computers use these. The small print on the label is the connector type. Students do not need to memorize it.

**GPU** — processing for pictures

A second processor, built to color many pixels at once

![Graphics card](https://upload.wikimedia.org/wikipedia/commons/thumb/f/f3/Nvidia_GeForce_GTX_970.jpg/960px-Nvidia_GeForce_GTX_970.jpg)

NOTE: Graphics Processing Unit. Games, video, and a lot of AI. The chip is under the fans. Some CPUs include a small GPU. A graphics card is a large separate one.

**Input** — information coming in

Keyboard, mouse, touchscreen, microphone, camera

**Output** — information going out

Screen, speakers, printer

Name the role

| Part | Role |
| --- | --- |
| RAM | <span class="fragment green">storage, temporary</span> |
| Keyboard | <span class="fragment green">input</span> |
| SSD | <span class="fragment green">storage, persistent</span> |
| Screen | <span class="fragment green">output</span> |
| CPU | <span class="fragment green">processing</span> |

---

## Operating Systems

An **operating system** is software

It lets programs use the hardware

NOTE: A Python program does not talk to the keyboard or the SSD itself. It asks the OS.

Hardware has no shared language

A **device driver** is the code for one part

Every program shares that driver

NOTE: A printer, a graphics card, and a keyboard each need their own driver. `input()` is one line. The keyboard driver is not your job.

**Multitasking**

Many programs look like they run at once

The OS decides who gets the CPU

NOTE: Process scheduling. One core does one thing at a time and switches thousands of times a second. Extra cores really do several things at the same moment.

**Users**

Accounts, passwords, and permissions

NOTE: This started as time-sharing: one expensive computer, many people taking turns. An administrator can install software. A normal account cannot. Programs get permissions too.

**Memory**

Each program gets its own slice of RAM

One program cannot read another's memory

NOTE: Called virtual memory. It can also lend a program extra space on the drive when RAM runs out. That borrowed space is much slower.

**Files**

The OS turns raw storage into files and folders

NOTE: You save `notes.txt`. You do not pick which bytes on the SSD it occupies. The file system tracks that, and who may open the file.

`print()` and `input()` ask the OS

The OS asks the hardware

The same Python file can run on Windows, macOS, and Linux

---

## Common Operating Systems

- Windows 
- macOS 
- Linux 
- Android 
- iOS

NOTES:
Rough share of all devices, phones included:
- Android 42%
- Windows 28%
- iOS 19%
- macOS 2%
- Linux 1%
Source: https://gs.statcounter.com/os-market-share/
Desktops are mostly Windows. Phones are mostly Android and iOS.

### Windows

![Windows desktop](https://cdn-dynmedia-1.microsoft.com/is/image/microsoftcorp/MSFT-PC-open-with-Start-menu-on-the-screen?scl=2)

Made by Microsoft

First graphical version in 1985

Built to compete with Mac

Timeline

- Windows 98 
- Windows XP 
- Windows Vista 
- Windows 7 
- Windows 8 & 8.1 
- Windows 10 
- Windows 11

![Windows XP](https://upload.wikimedia.org/wikipedia/en/6/64/Windows_XP_Luna.png?utm_source=en.wikipedia.org&utm_campaign=imageinfo&utm_content=thumbnail_unscaled)

![Windows 7](https://upload.wikimedia.org/wikipedia/en/5/50/Windows_7_SP1_screenshot.png?utm_source=en.wikipedia.org&utm_campaign=imageinfo&utm_content=thumbnail_unscaled)

![Windows 8](https://upload.wikimedia.org/wikipedia/en/8/8e/Windows_8_Start_Screen.png?utm_source=en.wikipedia.org&utm_campaign=imageinfo&utm_content=thumbnail_unscaled)

![Windows 11](https://upload.wikimedia.org/wikipedia/en/9/92/Windows_11_Desktop.png?utm_source=en.wikipedia.org&utm_campaign=imageinfo&utm_content=thumbnail_unscaled)

Files on Windows

File system: **NTFS**

A path looks like `C:\Users\Rylan`

Programs end in `.exe`

NOTE: NTFS is New Technology File System. `C:` is the main disk. A backslash separates folders.

### macOS

![macOS desktop](https://www.apple.com/newsroom/images/2024/09/macos-sequoia-is-available-today/article/Apple-macOS-Sequoia-hero_big.jpg.large_2x.jpg)

Made by Apple

First version (Mac OS) in 1984

Built so you barely notice the operating system

NOTE: Classic Mac OS "deliberately sought to minimize the user's awareness of the operating system" (Wikipedia). Closed source, like Windows.

![Mac OS Classic](https://upload.wikimedia.org/wikipedia/en/8/8a/MacOS81_screenshot.png?utm_source=en.wikipedia.org&utm_campaign=imageinfo&utm_content=thumbnail_unscaled)

Mac OS X (2001) was a rewrite built on Unix

Built on Unix

NOTE: The X is the Roman numeral 10. Today's names are places in California: Ventura, Sonoma, Sequoia. The terminal and file paths look a lot like Linux. A Windows `.exe` does not run here.

![Mac OS X](https://upload.wikimedia.org/wikipedia/en/d/d8/MacOSX10-0screenshot.png?utm_source=en.wikipedia.org&utm_campaign=imageinfo&utm_content=thumbnail_unscaled)

In 2016 the name was changed from **OS X** to **macOS**

![macOS Tahoe](https://upload.wikimedia.org/wikipedia/en/f/fa/MacOS_Tahoe_screenshot.png?utm_source=en.wikipedia.org&utm_campaign=imageinfo&utm_content=thumbnail_unscaled)

Files on macOS

File system: **APFS**

A path looks like `/Users/Rylan`

Officially runs only on Apple computers

NOTE: APFS is Apple File System. Forward slashes, and no drive letter.

### Linux

![Ubuntu desktop](https://upload.wikimedia.org/wikipedia/commons/thumb/6/64/Ubuntu_24.10_Oracular_Oriole_Desktop_English.jpg/960px-Ubuntu_24.10_Oracular_Oriole_Desktop_English.jpg)

A family of open-source operating systems

NOTES:
Distributions (distros): Ubuntu, Mint, Debian, Fedora, Arch.
Android and ChromeOS use the Linux kernel.

Most of the internet runs on Linux

Unlike Windows and macOS, it's free!

Used on a lot for servers

Used by hackers

Phones

**Android** — Linux, plus Google's software

**iOS** — Apple's phone OS, related to macOS

---

## Midterm Review

30 questions

~5 general CS

~25 Python

Only covers weeks 1-7 of class

First hour of class

Bring something to do when you finish!

Let's see what you know!

---

![Jimmy Fallon thats it](https://media4.giphy.com/media/v1.Y2lkPTc5MGI3NjExd2NmamM3NmR2c3RtenR3bGV5dnR1MnNyM3BzNnh3ZGNwYTFyZ2V6YyZlcD12MV9pbnRlcm5hbF9naWZfYnlfaWQmY3Q9Zw/uSZQ6WPIcpouUEpNTe/giphy.gif)