computer fundamentals & intro to c programming module i

Computer Fundamentals &

C Programming

Ajit K Nayak, Ph.D.S„O‟A University, Odisha

Module I

Contents

• Introduction to Computers

• Evolution of Computers

• Computer Generations

• Basic Computer

Organization

• Memory Hierarchy

• I/O devices

• Computer Software

• Planning Computer Program

• Computer Languages

• Introduction to C

programming

• Structure of C Programming

• Datatype

• Constant

• Variable

• Expression

• Conditional Expression

• Precedence & order of

evaluation

Introduction• Computer is a fast computing device

• Today‟s Computing refers to computer

supported commercial & scientific

applications.

• Example of computing

– Web services, Control system (missile, vehicular,

household device, Industry) . . .

• Is it comparable to human brain?

– It is fast but not smart!!!

Definitions• A computer is an electronic device that

performs arithmetic & logic operation at a

very high speed

• It is also called a data processor that can

store, process and retrieve data as and

when desired.

Input

(Data)

Process /

Manipulate

Output

(Information)

Evolution (1)• 1642: Blaise Pascal invented “Mechanical

Adding Machine”

• 1671: Baron Gottfried invented “Calculator”

for multiplication

• 1880: “Keyboard machines” designed in

USA

• 1880: Herman Hollerith invented “punched

cards” for input media & is used till late 70s

Evolution (2)• Charles Babbage is considered to be the

father of modern digital computers

– Designed difference engine in 1822

– Designed a fully automatic analytical engine in 1842

for performing basic arithmetic operations

– Established a number of principles that are

fundamental to the design of any digital computer

Well known Early Computers• MARK I computer (1937 - 1944)

– Electro-mechanical calculating device, 50 ft-long x 8 ft-high

– Add: 0.3 sec, mul:4.5 sec

• Atanasoff-Berry Computer (1939-1942)– Electronic machine to solve some mathematical functions

• ENIAC (1943-1946)– All electronic computer 20x40 sqft, add: 200 us, mul: 2000us

• EDVAC (1946-52)– Used stored program concept, instructions & data stored in

binary form

• UNIVAC I (1951)– First digital computer

Generation (I,II)

Generation (III)

Generation (IV)

Generation (V)

Basic Operations• Input

– The process of entering instructions and data to the computer system

• Store– Saving instruction & data to make them available as and when required

for processing

• Process– Performing arithmetic & logic operations on data using corresponding

instructions to produce information

• Output– To produce the information/result of the processing as a printed report or

visual display

• Control– Directing the manner and sequence in which all above operation are

performed

Basic Organization

Input

UnitOutput

Unit

Secondary Storage

Primary Storage

Control Unit

Arithmetic

Logic Unit

Program & DataStorage Unit

Information (Results)

Centarl Processing Unit

(CPU)

Data

Storage (Memory)• Primary Storage

– Used to hold data, ongoing job’s instructions, intermediate results

– Fast in operation

– Small capacity, expensive, volatile

– Ex: RAM, ROM, PROM, EPROM

• Secondary Storage

– Used to store stored program & data

– Slower, large capacity, cheaper, persistent

– Ex: Hard Disk, Magnetic Tape, Floppy, CD, Flash

Memory Hierarchy

Cache

Memory

MainMemory

On-line, Direct-access,

and sequential access secondary

storage such as hard disk

Off-line, Direct-access, and sequential

access secondary storage such as magnetic tape,

floppy disk, zip disk, worm etc

Mass storage device such as tape library, CD etc

CPU• Arithmetic & Logic Unit (ALU)

– Actual execution of the instruction takes place

– Arithmetic Operations like: add, subtract, etc

– Logic Operation: <, >, and, or, etc

• Control Unit (CU)

– Manages & coordinates all other components of a

computer system.

– It acts like a central nervous system of computer

– Ex: It decides when to execute which instruction

Input Devices• Keyboard

• Point & Draw devices

– Mouse, Trackball, Joystick

• Data Scanning Devices

– Image Scanner, OCR, Barcode reader, MICR

• Digitizer

– Used to pictures, maps etc to digital form

• Electronic Card

• Speech Recognition system

Output Device• Monitors

• Printers

• Plotters

• Screen Image Projector

CFCP / Module I / AKN / 19

Basic Terminologies• Hardware

– Physical devices of a computer system

• Software

– A Set of programs

• Program

– Sequence of instructions written using a computer

language to solve a small problem.

• Software Package

– A group of program that solve a specific type of job


H/W vs. S/W• S/W makes H/W usable

• They are complementary to each other

• Same H/W may perform different jobs using

different S/W


Types of S/W• System Software

– Are designed to control/manage and extend the

processing capabilities of a computer system.

• Application Software

– Designed to solve a specific problem or to do a

specific task.


Logical System Architecture

USERS

(Normally interact with the system via the user

interface provided by the application S/W)

APPLICATION SOFTWARE

(Software that do a specific task to solve a

specific problem)

SYSTEM SOFTWARE

(Constitute the operating and

programming environment)

HARDWARE

(Physical

devices/components of a

computer system)


Program Planning• To write a correct program, a programmer

must write each and every instruction in the

correct sequence

• i.e. it should be ensured that the

instructions are

– Appropriate for the program &

– In the correct sequence


Algorithm• Also called the ‘program logic’ is a step-by-

step description of how to arrive at solution

of a given problem.

• Algorithm has following characteristics

– Each and every instructions should be precise &

unambiguous

– Each instruction should be executed in finite time.

– After execution of all the instructions, it should

produce the desired result.


Example 1• Problem

– Mark-sheets of 50 students are available

– Calculate & produce the total number of student passed in ‘first division’

• Solution1. Initialize totalFirstDivision, and totalMarksheetsChecked to

zero.

2. Take the marksheet of next student and check the division.

3. If it is not first division go to step 5

4. Add 1 to totalFirstDivision

5. Add 1 to totalMarksheetsChecked

6. Check if totalMarksheetsChecked = 50 ? If no go to step 2

7. Print totalFirstDivision

8. Stop


Representation of Algo.• As flowcharts

– Pictorial representation of an algorithm

• As Pseudo code

– Is an imitation of actual computer instruction. i.e. it

written in English language, but looks like a

program.

• As Program

– Represented in the form of a programming language


Flowcharts

• Terminal– Start or stop

• Processing– Operations like add subtract etc.

• Flow ines– Flow / sequence of operation.

• Connectors– Required if the chart spreads over multiple pages

Terminal Input /

Output

Decision

Processing

Flow Lines

Connectors


Example Decision

Is I=10?No

Yes

Compare

A & BA>B

A=B

A<B

I = ?

= 0 = 1 = 2 = 3 = 4 = 5 . . .

Two – way

Branching Three – way

Branching

Multi – way

Branching


Example (1)• Find the % mark secured by a student, given all marks

Start

Read mark

details

Add marks of all

subjects giving total

Percentage =

total / totalSubject

Print

percentage

Stop


Example (2)• Find the % mark secured by 50 students, given all marks

Start

Read mark details

of one student

Add marks of all

subjects giving total

Counter = 1

Percentage =

total / totalSubject

Print

percentage

Add 1 to

Counter

Is Counter > 50NO

Stopyes


Flowchart Guidelines• Chart the main logic, then incorporate detail

• Do not chart everything in the chart. A

consistent level of detail to be maintained

• Names used should be prob. Specific

• Crossing of flow lines may be avoided

• Connectors may be leveled

• Construction should be left->right & top-

>bottom


Flowchart advantages• Better communication

• Proper program documentation

• Efficient coding

• Systematic debugging

• Systematic testing


Flowchart disadvantages• Very time consuming and laborious to draw

• Difficult to incorporate changes

• No standards available determining the

amount of detail to be produced


Pseudocode• Program logic is written in an ordinary

natural language

• Also called “Program Design Language” (PDL)

• Basic Logic (control) Structure

– Sequence

• Sequence of execution

– Selection

• Decision (branching)

– Iteration

• Repetition (loop)


Pseudocode example• Counter = 0

• Read first student record

• DO WHILE counter < 50

– Calculate totalMark

– percentage = totalMark / totalSubject

– Print percentage

– Counter = counter + 1

– IF counter < 49

• Read next student record

– END IF

• ENDDO


Classification of Languages• Low-level

– Machine Language

– Assembly Language

• High-level Language


Machine Language• Only language the machine understands directly

• Normally written as a string of binary numbers

• Example

– 000000 00001 00010 00110 00000 100000

– add the registers 1 and 2 and place the result in register 6

• Advantage & Limitation

– Fast execution

– Machine dependent

– Difficult to program or modify the program

– Error prone


Assembly Language• Uses alphanumeric mnemonic codes for the instructions in

the instruction set

• Needs an assembler (translator) to translate Assembly

language program into equivalent machine language

program.

• Example

– MOV AL, 61h

– Load AL with 97 decimal

• Adv & Limitation

– Easier to understand, code & modify

– Error tracing is easier

– Efficiency of ML

– Machine dependant

– Knowledge of H/W required


High level Language• Written in English like language with mathematical

symbols & expression.– Ex: FORTRAN, COBOL, PASCAL, BASIC, C, C++,

JAVA, . . .

• Machine independent

• Knowledge of hardware is not needed

• Another software (compiler, interpreter) is needed to translate the code to equivalent machine code.

• For different programs different translator software is required.

• Lower efficiency

• Less flexible to control Hardware resources.


Translators• Interpreter

– takes one statement of high level language, checks

for syntax error, translates to machine language

instruction and executes it.

– Then it considers the next statement & repeats above

process till the last statement.

• Compiler

– Checks and translates entire source program into

object program and not involved in execution.


C Programming Language• A General purpose programming language

with low level programming support. (“High-level assembly”)

• Currently, the most commonly-used language for embedded systems

• Very portable: compilers exist for virtually every processor

• Produces efficient code

• Fairly concise

• Structured, strictly-typed, case-sensitive


History• Developed between 1969 and 1973

along with Unix at AT & T Bell Labs,

USA

• Due mostly to Dennis Ritchie & Brian

Kernighan

• Designed for systems programming

– Operating systems

– Utility programs

– Compilers

– Evolved from B, which evolved from BCPLBrian Kernighan

Denis Ritchi


Character set• The set of characters which can be used to write a valid

token in C language

– Alphabates (a-z, A-Z)

– Digits (0-9)

– White Spaces (New line, Horizontal Tab, Blank Space)

– Special Characters

~ ! # % ^ & * ( ) _ - + = { } [ ] | \ : ; “ ‘ < > , . / ?

• Tokens

– The smallest element in the C language is the token.

– It may be a single character or a sequence of characters to form a single item.

• Tokens can be:

– Numeric constants, Character constants, String constants

Keywords, Names (identifiers), Operators ,

Punctuation Ex ; : , ‘ “ [ ] { } ( ) ,


C Keywords (I)• Certain words have a special meaning to

the C compiler.

• They are called reserved words or

keywords.

• We should not try to use these words as

names of variables or function names in a

program.

• The keyword list for C contains 32 words and all small-case letters.


C Keywords (II)User defined Data types

struct

union

enum

typedef

void

sizeof

Type Qualifier

short

long

signed

unsigned

const

volatile

Control Statements

if

else

do

for

while

break

continue

goto

return

switch

case

default

Datatypes

char

int

float

double

Storage Class

auto

static

extern

register


First Program in C1./* Filename: hello.c

2. Author: Brian Kernighan & Dennis Ritchie

3. Date written: ?/?/1978

4. Description: This program prints the greeting

5. “Hello, World!”

6. */

7.#include <stdio.h>8.9.void main()10.{11. printf(“Hello, world!\n”);12.}

Preprocessor Directive

Header file

“main” function special:

the entry point

I/O performed by a library function:

Comments

exit point


Comments (Line 1-6)• A comment is descriptive text used to help a

reader of the program understand its content

• Formal Comments (multiline):

/* Comment ….. */– Used for detailed description of functions or operations (for

our benefit, not compiler’s).

– Can take multiple lines in source file.

• Informal Comments (single line):

// Comment ….. Ends at the end of line– Used for quick comments like:

int temp; // temporary variable for storing // the input value


Preprocessor (Line 7)• Lines that begin with a # in column 1 are

called preprocessor directives (commands).

# include <stdio.h>

#include directive causes the preprocessor to include a copy of the standard input/output header file stdio.h at this point in the code.

#define -- define constants and macrosExamples:

#define e 2.7182818

#define pi 3.14159265359


C Program Structure (I)• Is a function oriented structured

programming language.

– Is a collection of functions.

– It should contain one & only one ‘main’ function and may contain any number of other functions.

– Beginning of main function is the entry point for program execution & end of main function is the exit point of program execution.


C Program Structure (II)/* Program Detail Comment */

<any global variable & function declarations >

main( )

{

<variable & function declarations & initializations>

<Input Section>

<Program Logic>

<Output Section>

} //end of the program


C Data Types and Variables• Data types are divided into 3 Category

– Basic data type (primitive data type)

– Derived data type

– User defined data types

• Basic data types: char, int, float, and double

• Variable (or Identifier) declaration syntax

– Data type <variable name>;

• Variable name can be of anything length. sensitive: abc is different from ABC

• Must begin with a letter and the rest can be letters, digits, and underscores.


Variable & Constants (I)• Integer variables: int a, b ;

• Integer constants: 1, 2, 3, . . .

• Integer variables, like a or b, store only whole

numbers like 3 or 7, not 3.33 or 7.65, and only up

to certain maximum values.

• Floating point variables: float c, d ;

• Floating point constants: 23.178, 0.34, . . .

• Floating point variables, like c or d, store rational

numbers, like 3.14159, but only a limited number

of digits of precision.


Variable & Constants(II)• double variables: double a, b ;

– Same as float but higher precession

• character variables: char a, b ;

• character constants: „a‟, „b‟, „\n‟,. . . ;

– Stored as an integer. (0-255). i.e. each character

const. is mapped to one integer of the above range


Basic Definitions• The type of an variable (object) determines the

set of values it can have and what operations can

be performed on it. Where

– set of values is finite

– When declaring a new variable and assigning a type for it,

you have to keep in mind the values and operations you'll be

needing.

• An operator computes new values out of old ones.

• An expression consists of variables, constants,

and operators combined to perform some useful

computation.


Datatypes• Normally Data types are divided into

following Categories

– Basic data type (primitive data type)• char, int, float, double

– Derived data type• array, pointer

– User defined data types• structure, union, enum

– A Special type• void


Basic Datatypes• Only 4 basic data types in C.

• char: a character, a single byte storage.

– how the computer stores characters?

– uses a character set, which is simply a mapping

between some set of characters and some set of

integers called ASCII character set,

– letter ‘A’ is represented by the code 65, ‘1’ is

represented by the code 49 etc.

– Number of characters possible?


Basic Types• int: an integer, reflects the natural size of integers

in the host machine– Find the size of storage & hence the range of vaules in your

machine

• float: a single precision floating-point number.– Find the storage size.

• double: a double-precision floating-point number– with more precision and perhaps greater range than float

– Find the storage size

• Qualifiers: may be used with basic types to increase/decrease the normal storage size. – long, short (int, double), signed, unsigned (char, int).


Constants (Integer)• A constant is just an immediate, absolute value

found in an expression.

• Decimal integer constants: 0, 1, 2, 123 .

• Octal integer:(0 used as prefix) 0144

• Hexadecimal integer const: (0x prefix)

• the constants 100, 0144, and 0x64 all represent

the same number.

• However, The compiler doesn't care; it always

converts everything into binary internally, anyway.

• A constant can be forced to be of type long int by

suffixing it with the letter L (upper or lower case)


Constants (Floating Point)• Floating point constant:

– 3.14, 10., .01, 123e4, 123.456e7 .

– The e indicates multiplication by a power of 10;

123.456e7 is 123.456 times 10 to the 7th, or

1,234,560,000.

– Floating-point constants are of type double by

default.


Constants (char & String)• Character constants: represented in single quote

– ‘A’, ‘f’, ‘t’

– May contain multiple symbols with escape char: ‘\n’, ‘\t’ etc.

• String constants. a string is a set of zero or more

characters;

– enclosed in double quotes: "apple", "hello, world", "this is a

test"

– a string containing one character is distinct from a lone

character?.

– A string is represented in C as a sequence or array of

characters.


Variable (I)• A variable is a place you can store a value. So

that you can refer to it unambiguously, a variable

needs a name.

• A declaration tells the compiler, the name and

type of a variable you'll be using in your program.

• In its simplest form, a declaration consists of

– the type, the name of the variable, and a terminating

semicolon (;)

– char c; int i; float f;

• Several variables of the same type may be

declared with separating coma in one declaration

– int age, rollNumber;


Variable (II)• A declaration for a variable can also contain an

initial value.

– This initializer consists of an equal sign and an expression,

which is usually a single constant:

– int i = 1; int a = i*3, i2 = func(20);

• Declarations may also contain qualifiers, storage

classes, and that we can declare arrays,

functions, pointers, and other kinds of data

structures.


Variable (III)• You can't place variable declarations just

anywhere! They must either be placed

– at the beginning of a function, or

– at the beginning of a brace-enclosed block of statements or

– outside of any function.

• Within limits, you can give your variables and

functions any names (identifiers) you want but

first 32 characters are significant.

– Names may contain alphabets, numbers, and underscores

– The names abc & ABC are different

– keywords can not be used as the names of variables or

functions (or as identifiers of any kind).


Operators• Used to operate upon operand (s)

• Arithmetic

– Binary: +, -, *, /, % Unary: -

• When applied to integers, the division operator /

discards any remainder,

– so 1 / 2 is 0 and 7 / 4 is 1.

– And 1 / 2.0 is 0.5, and 7.0 / 4.0 is 1.75.

• The modulus operator % gives you the remainder

when two integers are divided: 1 % 2 is 1; 7 % 4

is 3.

– 2.5 % 5.0 ?


Assignment Operators• The assignment operator „=„ assigns a

value to a variable. For example,

x = 1 sets x to 1, and a = b sets a to whatever b's

value is.

• Groups from right to left

c = a = b is equivalent to c = (a = b)

• Other Assignment Operators

+=, i.e. a += b; is equivalent to a = a + b;

Similarly, -=, *=, /+, %=, . . .


Increment/decrement Operators

• ++: increments the value of operand by one

• -- : decrements the value of operand by one

• Use

Postfix: i++; j-- is equivalent to i = i+1; & j = j-1;

Prefix: ++i; --j

++5 ?

• Difference

t = 5; x = t++;

k =3; y = -- k


Operators (IV)• Relational Operators

< , >, <=, >=, ==, !=

• Logical Operators

&&, ||, !

• Numeric value of a relational or logical

expression is 1 for true and 0 for false.

• Bit wise operators

&, |, ^ (ex-or), << (left-shift), >> (right shift), ~

(one’s complement)


Operators (V)• sizeof: size of variables/data types

– Use: sizeof(int)

• & -> address of

• * -> pointer

• ?: -> conditional expression (ternary operator)

– Use: y = (x = = 1) ? 10 : 20;

• , -> series opeartor


Precedence & Associativity• Precedence

– Which operator executes first

– i.e. 3 + 4 * 5 ?

• Their associativity indicates in what order

operators of equal precedence in an

expression are applied


Control Statements• The statement which controls the flow of

execution of a program is called control statement

Control Statement

Branching Statement Looping Statement

One Way Branching (if)

Two Way Branching (if else)

Multi Way Branching

If .. else .. if, switch .. case

Entry Control (while, for)

Exit Control (do … while)


if Statement (I)• Simple Syntax of an if statement is:

if ( expression )

statement ;

• If you have a series of statements, then enclose

them in braces:

if( expression )

{

statement1

statement2

statement3

}

Example:

if (x > max)

max = x;


if Statement (II)• Syntax of an if statement

is:

if ( expression )

{statement (s);}

elseif ( expression )

{statement (s);}

else

{statement (s);}

Example: if ( a < b )

printf ("a is less than\n") ;else if ( a == b )

printf (" a is equal to b\n") ;else

printf ("a is larger than b\n") ;


Assignments• Write a program to print the size of all

datatypes discussed

• Write a program to find largest of 3 integers,

using if statement

• Write the outputs for the following & explain

a=10;

if (a)

b=25

else

b=12


Readings• Pradeep K Sinha, Priti Sinha, Computer

Fundamentals

• Computer Fundamentals & C Programming

by Balagurusamy

computer fundamentals & intro to c programming module i

Education