Discussion 1

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# CS 61A – Discussion 1
## Allen Guo
## http://aguo.us/cs61a
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# Announcements

- Homeworks 0 and 1 due today

- Labs 0 and 1 due tomorrow

- Homework 2 due Tuesday

- Hog due next Thursday

- Midterm 1 is in two weeks
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## There's a lot of strange vocabulary in computer science...
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## Agile, AI, AngularJS, API, big data, cache, client-server, CPU, cryptocurrency, DAG, database, dependency injection, disk, filesystem, FSM, FTP, GNU, GPU, graphics, GUI, HTTP, interface, IoT, IRC, LAMP stack, Linux, loose coupling, machine learning, MVC, networking, Node.js, NoSQL, no-op, open source, OS, parallelization, PL, Python, RAM, React, redundancy, REST, robustness, SQL, SSH, TCP, threading, VCS, Vim, WWW, x86...
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# CS vs. Programming?

- CS is something you study, programming is something you do

- CS talks about what it is possible for *any* computer to do, programming solves problems for a specific computer (or subset of computers)

- CS is what you pay to learn, programming is what you get paid to do

.footnote[Source: [Quora](https://www.quora.com/Whats-the-difference-between-computer-science-and-programming) and [StackOverflow](https://softwareengineering.stackexchange.com/questions/137103/whats-the-difference-between-computer-science-and-programming)]
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# Terminal? GUI?

- Terminal/shell.red[*]: window that allows you to issue commands to your computer efficiently without using a GUI

- Bash: a specific kind of shell that is that's very popular

- GUI (graphical user interface): allows you to interact with your computer through graphical icons and visual indicators

- "At my internship I built a GUI for monitoring CPU usage"

.footnote[.red[*] Not actually the same thing, but are very close]
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# Inside Your Computer

- CPU (central processing unit): part of your computer that runs calculations and performs I/O

- CPU usage: how much "compute power" you're using

- I/O (input/output): reading and writing data

- Memory (RAM): place for your CPU to store intermediate values during computation

- Disk: place for storing things for the long term

- This is what you see when you open Finder or Windows Explorer

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# Quiz
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# Lecture Recap
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# Syntax Confusions

- `3.0` vs. `3`

- `3.0` is a float (fractional value) but `3` is an int (integer value)

- Floats are inaccurate: `3.0 + 1.9999999999999999` evaluates to `5.0`

- `/` vs. `//`

- `/` results in a float, `//` ("div") results in an int

- `return` vs. `print`

- `return` exits a function and indicates the result (return value)

- `print` displays output to the user (and does not exit the function)

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# Functions as Values

```python
def do_twice(f, x):
    return f(f(x))

def square(x):
    return x * x

print(do_twice(square, 3))
```

- What is printed when this code is run?

- Answer: `81`

- How many times is `square` called?

- Answer: twice

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# Functions in Functions

```python
def make_adder(n):
    def f(x):
        return x + n
    return f

add_two = make_adder(2)
print(add_two(add_two(0)))
```
- What is printed when this code is run?

- Answer: `4`

- How many frames are created total (not including the global frame)?

- Answer: three

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# Worksheet