CS 1110/1111 The Case for Computer Science CS 1110/1111 – Introduction to Programming

CS 1110/1111 The Course Goals 2 To teach the skill of programming To teach the art of computer science

CS 1110/1111 Look around… Where do you see computing at work in the world? 3

CS 1110/1111 A question First, what is an operating system? Second, how many operating systems have you used? 4

CS 1110/1111 Really? How many? Think of all the devices that contain operating systems of some kind… 5

CS 1110/1111 So I ask again… Where do you see computing at work in the world? Heck, look just in this room! In your dorm room / apartment! 6

CS 1110/1111 A system of interest SIS What's wrong with SIS? –(remember – we only have so much time in this class today…) 7

CS 1110/1111 Cri-SIS Thoughts? 8

CS 1110/1111 Okay, that was cathartic Now let's back up for a minute Why do we have SIS? –What's the underlying “problem” it's trying to solve? –Is this fundamentally a “computer science” problem? If so, what's the problem? If not, what discipline does it come from? Activity: A Cri-SIS –Groups of 3 or 4; Answers these questions 9

CS 1110/1111 A Big, Scary Computer Science Word “Algorithm” Definition? 10

CS 1110/1111 Algorithms – What do they mean? A step-by-step process for solving a problem A recipe! 11

CS 1110/1111 Well… what's a program? A program is an implementation of an algorithm that a computer can understand 12

CS 1110/1111 The Challenge 13 ElectricityFunctionality

CS 1110/1111 Abstraction Split up the problem into several layers Each intermediate layer will: –Use what its lower layer provides to do something –Hide the characteristics of the layers below it to the layer above The lower layers are in hardware and the higher layers in software 14 Get electricity into the computer Provide the required functionality to the user

CS 1110/1111 Let's Pause for a Moment What is a programming language? –A language that allows you to express computations performed by a “machine”. –But, a machine has several layers. Each layer has its own programming language! –The language allows the functionality provided by a layer to be used without knowing how it is implemented (Abstraction) What does a language do? –Provide representations for data –Define operations on the data 15

CS 1110/1111 Assembly Language (we're now in software land) Data: A collection of logical bits Operations: ADD, SUB, MULTIPLY,… (instructions) A sequence of instructions that perform a computation form a program. A program uses data that is stored in memory. 16.data hellostring:.ascii "Hello “.asciiz "World!\n".text main: la $a0, hellostring li $v0, 4 syscall li $v0, 10 syscall

CS 1110/1111 High-Level Language (HLL) Uses data representations and constructs that are much easier to use to convert the high-level computation steps (algorithm) to a computer program to achieve the desired functionality. 17