CS102 - Lesson 1

Programming Languages

• High Level - more powerful instructions, portable, simpler to understand and use - C, C++
• Low Level - machine languages and assembly languages

Programming Languages

• Interpreted - the computer will run the code by reading through the lines of your code
• Compiled - the computer will run a program that was optimized

Machine Code

• This is what the computer "understands"
• A computer "understands" a stream 1's and 0's.
• bit - a single 0 or 1 in binary
• byte - a sequence of 8 bits; can be represented as a number from 0 to 255
• A compiler converts C code into machine readable instructions

Getting Started

• unix machine
• OS terminal - for Apple computers
• WSL - Ubuntu - for Windows
• Other IDEs (Integrated Development Environments)

Commands

Directories

• cd directory -- change directory
• cd ..
-- go back a directory
• mkdir directory -- make directory
• pwd -- tells you where you currently are

Creating a Blank File

• touch filename -- creates a blank file or updates the timestamp of the file touched

File Access

• ls - list directories
• ls -l -- lists your files in a long format
• ls -a -- lists all files including those that begin with a dot
• ls -latrh -- lists all files in long format, in reverse order of the modification time, in human-readable form (use man to read more

File Access (cont.)

• mv filename1 filename2 -- moves a file; also renames a file
• cp filename1 filename2 -- copies a file
• rm filename -- removes a file
• rm -rf * -- removes everything!! Make sure you back things up; we will do that later with Github
• Note: * is a wildcard

File Access (cont.)

• diff filename1 filename2 -- diffs 2 files
• wc filename -- tells you how many lines, words, and characters are in a file
• chmod options filename -- changes the read, write, and executable access for a file
• If you're lazy, you can always do chmod 777 filename to enable all access for all types of users

Finding Stuff

• ff -- find files anywhere on the system
• grep string filename -- looks for a string in the files in the directory
• Note: there are many useful flags that you can use to make this stronger; see man grep

Editors

• vim
• emacs
• notepad++
• other IDEs (eclipse, etc.)

Note: Depending on the company you end up working for, you may not be able to install certain editors/IDE. You should learn one of the basics - vim or emacs.

vim Quick Guide

• vim filename -- to start editing a file with vim
• ESC :w -- write/save the file
• ESC i -- insert before the character
• ESC a -- insert after the character
• ESC :q -- quit vim

Writing a Bash Shell Script

#!/bin/bash

mkdir new_folder
cd new_folder
touch new_file.txt
ls

Running a Bash Shell Script

$ chmod 777 unix_commands.sh
$ ./unix_commands.sh

You should see a directory created with a blank file.

Setup to Program

Windows

• Set up Ubuntu for Windows WSL here.
• Set up gcc for Windows WSL here.

  sudo apt-get update
  sudo apt install gcc

  Mac

• Run gcc and install XCode

Parts of a C Program

• Consists of variables and functions
• Function - a sequence of statements
• Some functions are part of the C language itself and some are part of the libraries of ANSI C
• You have to tell the compiler which functions you plan on using
• Results in an executable file

Writing Your First Program

Start by writing hello.c:

$ vim hello.c

#include <stdio.h>
int main()
{
    printf("Hello, World!\n");
    return 0;
}

Compiling And Running Your First Program

$ gcc hello.c
$ ./a.out

The result should print:

Hello, World!

Setting Up Your Git Envir & SSH Keys

Setting up your github user name and email:

$ git config --global user.name "Your Name"
$ git config --global user.email "yourEmail@cooper.edu"

Set up your ssh key:

$ ssh-keygen -C "me@cooper.edu" -t rsa 
$ cat .ssh/id_rsa.pub

Copy the key and put it in your account settings.

More info can be found here: https://help.github.com/articles/connecting-to-github-with-ssh/

Creating a repo for hello.c

• Go to github.com
• Create a new repository and initialize with a README
• Clone with SSH and copy the link and run the following

  $ git clone git@github.com:yourUserName/repoName.git

Creating a separate branch

• To create a separate branch:

  $ git checkout -b helloBranch

• Copy your hello.c file into the directory and add and commit it with:

  $ git add hello.c
  $ git commit -m "first commit"

• Now push your branch to github:

  $ git push origin helloBranch

Creating a Pull Request & Merging to Main

• Go to the main github page and create a new pull request.
• The first branch is what you're merging into.
• Add some comments and click "Create pull request"
• You can now do a code review in the Files changed tab
• Lastly, click "Merge pull request" to merge it to the main branch.