1. Problem Solving and Computer Programming
Introduction
CMSC 104
Spring 1999
Problem Solving and Computer Programming
The critical words on this slide are "Problem Solving."
As you start off in computer science, there are two things you ought to know right away: it isn't about computers and it isn't a science.
The discipline we call "computer science" is really the study of algorithms --- of how to do things. An algorithm is a procedure to perform a specific task. In computer science, we're interested in discovering how algorithms work, how they can be measured, which ones are better than others, and how to build and use the best algorithms for any task.
This isn't a "science" because it's "active," we aren't just observing things, but trying to make them better.
It isn't really about computers because we are most interested in the algorithms themselves. Computers are just one means of actually executing them.

2. What is Computer Science?
Computer science is the study of algorithms --- specific recipes to accomplish a specific task.
Not “science” because because goal is to develop algorithms
“Computers” are just one means of executing the steps.

3. Am I in the right class? CMSC 104 CMSC 201
Assumes NO programming experience
Does NOT count towards your CS major
Prepares you for CMSC 201
CMSC 201
Assumes some programming experience
First CMSC course for CS majors
More challenging
If you can write a program in C, compile it on a Unix system, run it, and debug it if it doesn't work, then you don't belong in this class.

4. Why Study Computer Science?
The purpose of computing is insight, not numbers. R.W. Hamming
When you can measure what you are speaking about and express it in numbers, you know something about it, and when you cannot measure it in numbers, your knowledge is of a meager and unsatisfactory kind Kelvin

5. Getting a “GL” account at UMBC
You MUST have a GL account
Go to room ECS 005 (in the basement)
Sign-on to one of the PCs there
Login ID = register
No Password
Follow the instructions
Primary account for homework and projects.
You can log in from labs on Campus or from home over the internet or a telephone line.

6. Changing your Unix password
Login by entering your id and password given on the sheet
At the Unix prompt type: passwd <Return>
You will be prompted for your new password; type it in and press <Return>
You will be asked to type the new password again

7. Changing your Unix password (cont’d)
You will be given a message that the password has been changed
OR you will be given a message that rejects your new password
Passwords should be at least 5 characters long, should be something you will remember.
Your password will be rejected if it is a commonly used word or name
You must change your password. This should be a simple task, but it can be maddening. The purpose of a password is to keep other people from using the computer while masquerading as you. The operating system assumes that anyone who is entitled to use your account will know your password and that anyone who knows your password is entitled to use your account.
Now, since computers first had users, it has been a constant game for some users to masquerade as others. Some people do it purely for the thrill of pulling it off. Some people do it so they can use someone else's time or disk space. And some people do it so that they can raise havoc while someone else gets the blame.
In any case, you'll be much better off of no one has your password except you.
The secret is to have a password that's too hard to guess, but so easy for you to remember that you don't have to write it down (because someday you'll lose the paper and someone else will find it).
This isn't as easy as it looks. Crackers don't sit around and guess passwords themselves, they write programs that try every word --- and pair or triple of words --- in the dictionary.
So "habadashery banana" isn't good enough.
The trick is to blend in some numbers or punctuation in a way that you'll remember but won't be easy to figure out. So we get "haba-ery b&&a" or "^field&mccoy".
One more thing: it took me a frustrating half hour before I realized that the password must be at least 7 characters long.

8. Computer Science at UMBC
CSEE Administrative Offices
ECS 210
CSEE Student Services Office
ECS 201
CSCM (Sea Scum)
Computer Science Council of Majors
CSHC (Computer Science Help Center)
ECS 332 In the Mechanical Engr Dept.

9. Some Example Passwords
Possible Candidates (but find your own)
tomcat
g0lf3r golfer
saleboat (sailboat)
Known Loser
Stratford (too short?)
“Second” passwords seem to be easier.

10. UCS Labs
University Computing Services are responsible or all the computers
24 hour labs
ECS IBMs, MACs
Open Labs
ECS SGI Workstations
ECS IBMs (but not 104A)
ECS 122A -- IBMs
Print Dispatch -- ECS 019 ($$)

11. UCS Labs (Cont'd) Open, but sometimes reserved Hours of Operations
ECS IBMs
ECS MACs
Hours of Operations
Monday - Thursday 7 AM - 3 AM
Friday 7 AM - Midnight
Saturday 8 AM - Midnight
Sunday Noon - 3 AM

12. Consultants vs Tutors UCS Labs are staffed by consultants
using software (pine, xrn, netscape, etc.)
some text editors (emacs, pico)
operating system commands (Unix)
cleaning floppy disks
communicating with UMBC computers
CSHC is staffed by tutors
Help with homework and projects
emacs and Unix questions
ECS Hours to be announced

13. Logging on from Home 2400 baud lines 744 - 8000
high speed lines
14.4 or 28.8
Settings for both lines
No parity, 8 data bits, 1 stop bit
On your computer, you must have
Communications software (e.g.. Procomm Plus)
A modem

14. telnet Connect to your Internet Service Provider (ISP)
Windows 95/NT/98
Start
Run
telnet gl.umbc.edu

15. Hardware & Software Needs
Do I need my own computer?
No, but it is more convenient for you
If I have my own computer, can I use it?
Sure, but you will using it mostly to login to your GL account or for word processing
Do I need a C Compiler?
No, and if you buy one, you’ll be wasting your $$$. All programming should be done in your GL account.

16. Course Overview Introduction to Computer Organization and Architecture
Data Representation and Memory Usage
Introduction to Operating Systems
Problem Solving and Algorithm Development
Introduction to Software Engineering Using Top-Down Design
Compiling, Linking and Execution
C Programming
Reuse Based on Algorithm Selection and Design Techniques