Computing Fundamenatls CMSC 201 Computer Science I Penny Rheingans University of Maryland Baltimore County (with inspiration from previous 201 instructors and the creators of UMBC’s CMSC 101 and HMC’s CS5)

Learning Objectives To have a very basic overview of the components of a computer system To understand how data is represented and stored in memory To be aware of elements of the UMBC computing environment

Computing Systems Hardware Components Software Components Central Processing Unit (CPU) Auxiliary Processors (GPU, etc) Memory Bus Network Connection External Devices: keyboard, monitor, printer Software Components Operating System: Linux, MacOS, Windows, etc Applications

Binary Representation All information is store in a binary representation (ie, it’s all 1s and 0s): code, text, images, sounds For each type of item/object, there are specific formats that define who to represent that thing (character, digit, sound, image, etc) in binary But why use binary?

But why binary ?

Place Value Notation

Converting from Binary What are the decimal equivalents of: 101 1111 100000 101010 101 = 5 1111 = 15 100000 = 32 101010 = 42

Converting to Binary What are the binary equivalents of 9 27 68 1000 9 = 1001 27 = 11011 68 = 1000100 1000= 1111101000

UMBC Computing Environment We will develop our programs using UMBC’s GL system GL is running the Linux Operating System GUI interface – Graphical user interface Command-Line Interface – When you connect to GL using SSH Lab 1 will walk you through using the UMBC computing environment

How do I connect to GL? Assuming you have Internet access, use SSH Windows Download Putty (Lab has a video about this) Hostname – gl.umbc.edu Make sure you pick SSH Put in username and password Mac SSH client already installed Go to the Application folder and select Utilities Open up a terminal Window Type ssh -l username gl.umbc.edu Put in your password

Linux Commands See: For now, let’s just learn: http://www.csee.umbc.edu/resources/computer-science- help-center/#Resources For now, let’s just learn: ls – list Display the files and directories in your current directory cd – change directory Directory is another word for folder .. = parent directory . = current directory mkdir- make directory Note: Commands are case-sensitive

Directories Can contain files and other directories (calledsubdirectories) /afs/umbc.edu/users/first/second/username/home 201 myOtherClass lab1 When you log into Gl, you will be in your home directory use the cd command to go to subdirectories HW1 lab1.py

emacs Reference: emacs – a text editor http://www.csee.umbc.edu/summary-of-basic-emacs-commands/ emacs – a text editor We will generally use emacs to write our python code To open a file that you want to call example.txt (replace example.txt with your file name): Type: emacs example.txt To save a file: CTRL X and CTRL C To reopen the file: To remove the file Type: rm example.txt