Chapter1_IntrotoC

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CSEB114: PRINCIPLEOF PROGRAMMINGChapter 1: Introduction to Computer andProgramming


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Objectives

In this chapter you will learn about:

Overview of PC components

The different types of language

Natural Language

Formal Language

Functional / Imperative Language

Programming Languages

C as an imperative language

C program at a glance


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Overview of PC Components

Section 1


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Computer Hardware

Components

Components of a PC


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Input / Output Devices

Input DevicesAccepts information from the user and

transforms it to dig i tal codes that the

computer can processExample: keyboard, mouse, scanner

Output Devices

An interface by which the computerconveys the output to the user

Example: monitor, printer


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Central Processing Unit (CPU)

Does most of the work in executing a program

The CPU inside a PC is usually the

microprocessor

3 main parts:Control Unit Fetch instructions from main memory and put them in

the instruction register

ALU (Arithmetic Logic Unit) Execute arithmetic operations

Registers Temporarily store instructions or data fetched from

memory


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Storage Devices

A magnetic device used to store a large

amount of information.

Store the software components or data

needed for the computer to execute its

tasks.

Could be read only or writable.

Example: Hard drive, CD ROM, floppy

disks


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Network Devices

Connect a computer to the other

computers.

Enable the users to access data or

execute programs remotely.

Example: modem, Ethernet card


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The different types of language

Section 2


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Semantics and Syntax

Semanticsthe meaning of the language

within a given context

Syntax - Syntax are the rules to join words

together in forming a correct expression

or phrase.

In natural languages it is often possible to

assemble a sentence in more than one

correct ways.


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Formal Language

Language with limited, defined, words

Each concatenation of words ('phrase') has a

single, clearly defined meaning

no (miss-)interpretation possible

Sometimes called Context Free Language

To 'talk' to a computer; to instruct a computer;

our commands must be 100% clear andcorrect.

Often there is only a single, correct syntax.


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Functional / Imperative

Language

Functional Language:

Tell what to do, but not how:

sum [1...10]

Imperative Language:

Tell what to do, but mainly how:

Take number 1 and add the next number to it;

then add the next number to the sum; and so on;until you have reached 10 as number to be

added. Then print the sum of all numbers


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What is Programming?

Programming is instructing a computer to dosomething for you with the help of aprogramming language

The two roles of a programming language:Technical: It instructs the computer to

perform tasks.

Conceptual: It is a framework within which we

organize our ideas about things andprocesses.

In programming, we deal with two kind of things:

Data- representing 'objects' we want to

manipulate


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Programming Language

Formal Language used to communicate

to a computer.

A programming language contains

ins t ruct ions for the computer to perform

a specific action or a specific task:

'Calculate the sum of the numbers from 1 to

10

'Print I like programming

'Output the current time'


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Programming Language

Can be classified into as a special-purpose and

general-purpose programming languages.

Special-purpose : is design for a particular type

of application Structured Query Language (SQL)

General-purpose : can be used to obtain

solutions for many types of problems

Machine Languages

Assembly Languages

High-Level Languages


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Machine Language

The only language that the processor actually

'understands

Consists of binary codes: 0 and 1 Example: 00010101

11010001

01001100

Each of the lines above corresponds to a specific task to

be done by the processor.

Programming in machine code is difficult and slow sinceit is difficult to memorize all the instructions.

Mistakes can happen very easily.

Processor and Architecture dependent


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Assembly Language

Enables machine code to be represented in words and

numbers.

Example of a program in assemb ler language:

LOAD A, 9999

LOAD B, 8282

SUB B

MOV C, A

LOAD C, #0002

DIV A, C

STORE A, 7002

Easier to understand and memorize (called

Mnemonics), compared to machine code but still quite

difficult to use.

Processor and Architecture dependent


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High-Level Language

Use more English words. They try to resemble English

sentences. Therefore, it is easier to program in these

languages.

The programming structure is problem oriented - does

not need to know how the computer actually executes

the instructions.

Processor independent - the same code can be run on

different processors.

Examples: Basic , For tran , Pascal, Cobo l, C, C++,

Java

A high level language needs to be analyzed by the

compiler and then compiled into machine code so that

it can be executed by the processor.


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C Programming Language

Why 'C' ?

Because based on 'B'; developed at Bell

Laboratories

Developed by Dennis Ritchie at BellLaboratories in the 1960s

In cooperation with Ken Thomson it was used

for Unix systems The C Language was only vaguely defined, not

standardized, so that almost everyone had his

own perception of it, to such an extend that an

urgent need for a standard code was creeping


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C Programming Language

In 1983, the American National Standards

Institute (ANSI) set up X3J11, a Technical

Committee to draft a proposal for the ANSI

standard, which was approved in 1989and referred to as the ANSI/ISO 9899 :

1990 or simply the ANSI C, which is now

the global standard for C. This standard was updated in 1999; but

there is no compiler yet


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C as An Imperative Language

Section 3


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CAn Imperative Language

C is a highly imperative language

We must tell it exactly how to do what;

the means and functions to use;

which l ibrar ies to use;

when to add a new line;

when an instruction is finished;

in short: everything and anything

Hint: Observe the syntax in the next slide


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C Program at a Glance

Section 4


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A Simple Program in C

#include

int main()

{

printf("I like programming in C.\n");

return 0;

}


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A Simple Program in C -

explanation

#include

int main()

{

printf("I like programming in C.\n");

return 0;

}

standard Library, input-output, header-file

Begin of program

End of statement

End of Segment

Start of Segment

Function for printing text

Insert a new line


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C Output

I like programming in C.


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Summary

We have looked at some underlying hardware

We have seen some different types of

languages;

the relevance of semantics and syntax.

We have observed the detail necessary in an

imperative language to instruct a computer

properly. Finally, we examined the syntax to print a line

of text to the screen of our computer.

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