1. 1 Please switch off your mobile phones

2. 2 Prolog: The Initiation ET: Hey Alice! What is this on your desk? Alice: That’s a digital computer. ET: Digital what? Looks pretty unsocial. Doesn’t even greet me! Alice: It helped us discover you and your solar system. ET: Wow! That sounds cool. How do you use it? Does it talk? Alice: It can solve hard problems. You have to program it to do that. ET: Will you teach me do that?

3. 3 WELCOME To ESC101N: Fundamentals of Computing Instructor: Mainak Chaudhuri mainakc@cse.iitk.ac.in

4. 4 Agenda Administrivia What this course is not about Anatomy of a computer

5. 5 Administrivia Lecture hours –Monday, Wednesday, Thursday: 9-10am, L17 –Please come to class in time Labs –2pm-5pm, 11 lab sessions –Monday: B5-B6, Tuesday: B1-B2, Wednesday: B9-B10, Thursday: B7-B8, Friday: B3-B4 –No lab this week Tutorial –Tuesday 9-10am, Tutorial Block 101-110 –No tutorial this week

6. 6 Administrivia Grading [this is the sad part] –Exam: 15+15+30 –One compulsory lab test: 10 –Project or another lab test (your choice): 20 –Weekly lab sessions: 10 –Two surprise quizzes: 10 (this is extra) Held in tutorial sessions No make up for surprise quizzes (so come to tutorial regularly) –Project proposal submission deadline: any time before 1 st October Can get started even today if you know Java

7. 7 Administrivia There will be a course web page with all info –Temporarily: www.cse.iitk.ac.in/~mainakc/esc101notes.html Text book –Nothing specific: your choice –Suggestion: “Java Elements: Principles of Programming in Java” by Bailey and Bailey –More references are on the webpage Visit past course sites: www.iitk.ac.in/esc101

8. 8 For Visitors and Wanderers Also known as audit students In case you want to experience the “excitements” of the tutorials and labs –Send your section preference to me so that we can be prepared to accommodate you –But not allowed to sit in the lab tests –Can do a project, but will not be graded –Can write quizzes, but will not be graded –Not allowed to take the exams In case there are too many visitors, we will not allow anyone in the tutorials and labs

9. 9 What this course is not about This is not a course on programming –You will learn how to solve problems with computers: especially the ones that you cannot solve with paper and pencil quickly –The greater part of the lectures will be devoted to the concepts involved in developing a computer algorithm Sequence of steps that solve a problem –Java will be used as a vehicle to demonstrate the concepts Do not expect to become an expert in Java after taking this course

10. 10 Anatomy of a computer What you see –A monitor, a keyboard, a mouse, a printer … –Input/Output devices –Through these you ask the computer to do something and the computer tells you the results Need a way to convey your commands to the computer (it is really a stupid device which cannot do anything on its own) –Internally A central processing unit and a scratchpad (often called main memory) accomplish the job

11. 11 Anatomy of a computer Central processing unit does not understand English, not even Java –It only understands two symbols: 0 and 1 –These are called bits (short for binary digits) –You encode your algorithm into a high-level language called Java This is called a program This is harder to understand than English, but easier to understand than a 0-1 encoding How do I encode a program in 0-1? This is used only for storing the program in main memory

12. 12 Anatomy of a computer A friend of yours called compiler translates the program into a binary encoding called an object program –This is almost understandable to the central processing unit (often called a microprocessor) Another friend of yours called a linker adds something more to an object program to convert it to an executable –This is understandable to the CPU –But somehow it needs to get started executing

13. 13 Anatomy of a computer A big boss called operating system loads the executable in main memory and hands over the control to the CPU –Now the CPU starts executing your program (essentially the binary executable) –Once in a while it prints something on the monitor and you appreciate that Notice that it is not doing anything on its own, only doing whatever you have asked it to do –At some point the CPU completes the execution and you have all the results

14. 14 A simple program Let’s write a program in English (almost) –Want to add five numbers a, b, c, d, e and print the result on monitor print (monitor, a+b+c+d+e) –print is used as a function which takes two arguments: where to print and what to print –A binary translation of this could convert each character i.e. p, r, i, n, t, (, m, … into a binary string e.g., p is the 16 th alphabet, so represent it as 16 zeros; put a 1 to mark the end of a character –Now I can design a CPU which can understand this translation and execute my program (caution: this is just an example)

15. 15 “The Computing Stack” Problem Algorithm Program (HLLs) HLL Compiler/Linker Executable binary Operating System Microarchitecture Circuits Transistors ESC101N HLL=Java Central in CS Hardware/ software interface Hardware

16. 16 Next week’s lab Learn to use the UNIX environment –How to create a file (this is where you store your programs) –How to create and navigate through directory (this is where you store your files) –How to copy files from one directory to another –And more: www.iitk.ac.in/esc101/linux.pdf –Lab is upstairs in CC: TAs will be present at the front door to lead you