Senem Kumova Metin 2010-2011 Introduction to Programming CS 115 Introduction to Computing PART I : Computer Basics PART II: Introduction to Computing/Programming

Senem Kumova Metin 2010-2011

Introduction to Programming CS 115

Introduction to Computing

PART I : Computer BasicsPART II: Introduction to Computing/Programming


PART I : Computer Basics

Contents

• Computer basics

• Hardware & software

• Hardware components


What is a Computer?

• A computer is a machine that manipulates data according to a list of instructions

• Simply a computer

1. takes information (or inputs)2. processes it according to a set of instructions

(a program) 3. gives back a result (or output)


Computing• Activity of using and developing computer

technology, computer hardware and software.

• Hardware – a general term that refers to the physical artifacts of

a technology • Software

– a general term used to describe a collection of computer programs, procedures and documentation that perform some tasks on a computer system


Key components of a Computer



• Input Devices

– Receiving sections of computer– Allow the user to control the machine– Examples :

• Keyboard • Mouse • Microphone • Scanner• Etc..



• Output Devices

– Return the results of computer actions back to the user

– Examples :• Monitor • Speakers • Printer



• CPU ( Central Processing Unit)

– ‘brain’ of the computer

– Follows the instructions provided by both the user (via input devices) and the program that is running in order to perform a task

– Involves a control unit, ALU (Arithmetic Logic Unit), registers...


Key components of a Computer• Memory

– Internal storage areas in the computer

– Retains information that has been entered through the input unit so that the information may be made available for processing when needed.

– RAM and ROM

• RAM - Random access memory: whose contents can be accessed (read, write and remove) in any order

• ROM - Read-only memory: On ROM, data is prerecorded for read only which can not be removed


Key components of a Computer• Secondary Storage

– Long term high capacity warehousing part of the computer

– Store both the programs that run on the system as well as the work that is created

– The most common storage device is a fixed

magnetic disk that sits inside the machine and this is called the hard drive

– Examples: hard disk, CD,DVD and flash drives


PART II : Introduction to Computing/Programming

Contents

• Computer programming

• Flow of Control

• Programming languages

• Programming in C


WHAT is PROGRAMMING??scheduling or performing a task or / and event

WHAT is COMPUTER PROGRAMMING??creating a sequence of steps for a computer to follow in performing a task


WHAT is a PROGRAMMING LANGUAGE ?

• A set of rules, symbols, and special words used to construct a computer program


Programming language rules consist of

– Rules of Syntax which specify how valid instructions are written in the language

( natural language rule subject + verb +object )

– Rules of Semantics which determine the meaning of the instructions (what the computer will do)( A book has bitten a car )


Programming Languages

• Machine Languages

• Assembly Languages

• High Level Languages


Machine Language

• Machine dependent

• Machine code is a set of instructions that a computer's central processing unit (CPU) can understand and obey directly, without any translation.

• Machine-code programs consist entirely of binary digits (bits).

• BIT ?? BYTE??


Assembly Language

• First attempt at producing a mechanism for writing programs that was more palatable to ourselves

• A program written in assembly code, in order to “run”, must first be translated (assembled) into machine code.


High Level Languages

• A more problem-oriented (rather than machine-oriented) mechanism for creating computer programs would also be desirable

• Hence the advent of high(er) level languages starts with the introduction of “Autocodes”, and going on to Algol, Fortran, Pascal, Basic, Ada, C, etc

• Interpreted or compiled


• Machine Language

+1300042774+1400593419+1200274027

• Assembly Language

Load basePayAdd overTimePayStore grossPay

• High level Language

grossPay= basePay+overTimePay

Classification of High level Programming languages

• Programming paradigm : Alternative approaches to the programming process

– Functional (Lisp, ML)– Object-Oriented (C++, Java)– Imperative (Procedural) (Fortran, Algol, Pascal,

Basic, C)– Declarative (Prolog,GPSS)



High Level Languages• Interpreted

– Interpreted Languages are read and then executed directly, with no compilation stage.

• Compiled

– Compiled Languages are transformed into an executable form before running.


ASSEMBLY versus HIGH LEVEL LANGUAGE

HelloWorld.asm

Source Code

HelloWorld.c

Source Code

Machine Code (binary) Machine Code (binary)

Object Codeassembled

compiled

Library

(stdio.h)linked


Compilation Process


High Level Languages: Libraries

• Libraries (in computer programming terms) contain chunks of precompiled (object) code for various functions and procedures that come with a programming language that requires compilation

• For example functions and procedures to facilitate I/O


Flow of Control

The execution sequence of a group of machine instructions is known as the flow of control.


EXAMPLE 1: Flow of Control

SCENARIO :

we have 2 integers : x, y

multiply x with y

store the result in x

print the value of x

int x and int y

x = x*y

print x


EXAMPLE 2: Flow of Control

SCENARIO :

we have 2 integers : x,y

if x is greater than 0 then

do x= y+1;

else

do x= y-1;

print the value of x

int x and int y

x > 0

YES NO

x = y+1 x = y-1

print x


Why C?

• Native language of UNIX (a famous operating system)

• Standard development language for personal computers

• Portable (can be moved to other machine !)

• Powerful set of operators and powerful libraries (some operators: ++,--….)

• Basis for Java, C++…..


First C program

– Basic I/O functions : printf / scanf– Including libraries– Writing comments– Defining variables ….


Basic I/O Functions: printf

#include <stdio.h> // library file

void main(void)

{

printf("from sea to shining C\n");

}

// Print a string of characters to the screen


Basic I/O Functions: printf

#include <stdio.h>

void main(void)

{

printf("from sea ”);

printf(“to shining C\n");

}


Basic I/O Functions && Defining a variable

#include <stdio.h> // library file

void main(void)

{ int x=0;

// an integer variable is defined and it is

// initialized to 0

printf(“%d“, x);

// print current value of variable x as a decimal value

}


Basic I/O Functions : scanf

#include <stdio.h>

void main(void)

{ int x=0;

printf(“%d\n”, x); // print x as a decimal value

scanf(“%d”,&x); // read a decimal value from keyboard, store it in x

printf(“%d\n”, x); // print x as a decimal value

}

Documents

Senem Kumova Metin 2010-2011 Introduction to Programming CS 115 Introduction to Computing PART I : Computer Basics PART II: Introduction to Computing/Programming