CS102B - Lesson 1

A Bit About Computers

• System Software - provides a user interface and tools that allow the user to access and use different components of the computer
• Application Software - helps users solve problems and accomplish tasks

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
• Cygwin - for Windows
• When installing, install everything that has gcc, g++, git, and its dependencies.
• You can install everything if you want, but it will take a while and a lot of disk space.
• Other IDEs (Integrated Development Environments)

For the purpose of this class, I will be using Cygwin.

Commands

Directories

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

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

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 & Shell Scripts

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
						

Hello World

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