1 TOPIC 1 INTRODUCTION TO COMPUTER SCIENCE AND PROGRAMMING Topic 1 Introduction to Computer Science and Programming Notes adapted from Introduction to Computing and Programming with Java: A Multimedia Approach by M. Guzdial and B. Ericson, and instructor materials prepared by B. Ericson.

Outline  What is Computer Science  Some of the roles of Computer Science in our society  What is in a computer  What is programming  What is a program  What a compiler does  Some specificities of Java 2

What is Computer Science? 3  The design, analysis, implementation, …  of algorithms,  that solve problems. Why study Computer Science?  computing is part of everything we do  develops your problem solving skills  Lots of jobs!  Network and data analysts, software engineers are projected to be some of the fastest growing professions,

Roles of Computer Science  Maintaining the technical infrastructure  network, software  But also many algorithmic challenges  AI for games  search or auction algorithms (Google, Bing)  medical imaging  cryptology (RIM)  low-power chips 4

CPU and RAM 5  Central Processing Unit (CPU) (processor) executes instructions  Main Memory (RAM)  Internal storage that holds the programs (instructions and data) currently executed  Made of switches, each of which represents 0 or 1 and is called a bit (binary digit)  Information is lost when power is turned off

External memory and I/O 6  Secondary Memory: hard disks, CDs, DVDs, USB sticks  Provide long-term storage  Organized as files, each of which has a file name and a folder (directory) that contains it.  Input/Output (I/O) units: keyboard, mouse, screen, printer, webcam, etc.  Used for communications with the user

What is programming? 7  Programming is the process of creating detailed instructions that a computer can execute to accomplish some task  It is much like:  writing a recipe for your favorite dish  giving someone directions to your house  making a robot do what you want

What is a program? 8  Programs consist of  Instructions to perform a task  Data values used in performing the task  Programs are written in a language that a computer can understand  System.out.println(…) prints to the screen public class HelloWorld { public static void main(String[ ] args) { System.out.println("Hello World!"); }

High-level languages 9  Programmers usually write programs in high-level languages  Java, C, C++, C#, Visual Basic, Python, Scheme, Lisp, Pascal, Fortran, etc. etc.  People-oriented: created to make it easier for programmers to write complicated programs  Machine independent: not written for any particular kind of computer (Intel, Mac, etc.)  But computers do not understand high-level languages directly

Machine language 10  The machine language consists of the set of instructions that the CPU can execute directly  Instructions to the CPU (to add, subtract, read, store, etc) are made up of 0’s and 1’s  Machine dependent: each type of computer has its own machine language

High-level to machine language 11 High-Level Language Program (source code) Compiler Machine Language Program (executable code) CPU

Java 12  A high-level language developed by Sun Microsystems in the early 1990s  Cross-platform  Object-oriented (later)  Widely used in business, science and education  One of the fastest-adopted technologies of all time!  Different from previous high-level languages

From program to execution 13 Java Compiler CPU Java source code Bytecode Java Virtual Machine

Summary 14  Terminology introduced:  CPU, RAM  Bit  Program  High-Level Language  Machine Language  Compiler  Bytecode  Java Virtual Machine