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TA ZC142 Computer ProgrammingLecture 2Date: 28/07/2012

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Last Lecture

Introduction to Computer Representation of Data

Programming LanguageC Programming Language

Basic Structure

Simple C Program

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Today s Lecture

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Structure of a C Language Program

/* Program to compute . */ #include /*Library files inclusion */

int main(void){

/* local variable declarations *//* initialization */

/* statements */

return(0);}

Returns 0 to the OS after execution.

Void indicate that main( )receives no data from OS

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Simple C Program

#include#define KMS_PER_MILE 1.609

int main (void){

float miles, kms;/* Read distance in miles */printf( Enter distance in miles \n);scanf (%f, &miles);

/*Convert the distance to kms*/

kms = KMS_PER_MILES * miles;

printf( Distance in kms = \t %f ,kms ) ; // Display the resultant distance in Kms

return(0);}

Preprocessor directive

Standard Header File

constant

Reserved Words

Variables or User defined identifiers

StandardIdentifier

Comments

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C Character Set

Uppercase letters A to Z , lower case letters a toz, digits 0 to 9

Special characters.e.g. + , - , *, &, ?, /, \ , #, (, ), {, },[, ], , ==, =, ;, :, ,etc

Escape sequencese.g. \n (new line character), \t (horizontal tab), \v(vertical tab)

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Variables & Constantsin Programming Language

Variable

It s a name associated with a memory cellwhose value can be changed. All variables must be declared before theycan appear in executable statements

It consists of a data type, followed by oneor more variables.E.g. double miles, kms;

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Variables

Invalid Remark Valid

5thplayer First char is number player5x First char is not letter xOrder-no - is not allowed Order_nodouble Double is a reserved

worddoubletype

count value Blank is not permitted Count_value

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Variables & Constantsin Programming Language

ConstantIt s a name associated with a memory cell whose

value can not be changed.Declared by #define directive.

E.g. #define KMS_PER_MILE 1.609 const int x = 300;

const char c = A ;

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Data Types

It is a set of values and a set of operations onthose values.

Primary Data typesDerived Data types (discussed later)User defined data types (discussed later)

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Primary Data Type

Data type Description Memory Requirementint Integer quantity 2 bytes

char Single character 1 byte

float Floating pointnumber

4 bytes

double Double precision 8 bytes

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Assignment Statement

It stores a values or a computation resultin a variable

It is used to perform arithmeticoperations in a programe.g. kms = KMS_PER_MILES * miles;

Assignmentoperator

Multiply operator

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printf() Function

printf( Distance in kms = \t %f ,kms ) ;

Function namefunctionarguments

Format Stringprintlist

Escapesequence

placeholder

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scanf() Function

scanf ( %d %d, &age, &year);

Function name

Format String

Addressof operator

Variables

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Sample Program#include /* program to display use of I/O and data types */int main(){ int marks;

float average;char grade;

printf(Enter your marks: \ n); scanf(%d, &marks); printf(Enter average marks: \ n);

scanf(%f, &average); printf(Enter your grade: \ n);

scanf(%c, &grade); printf(Marks = %d \ n,marks); printf(Average = %f \ n,average); printf(Grade = %c \ n,grade);

return (0);

}

InputEnter your marks:70Enter average marks:50.5Enter your grade:

A

Output

Marks = 70 Average = 50.5Grade = A

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Arithmetic Operators

Operator Meaning+ Addition or unary plus

- Subtraction or unary minus* Multiplication

/ Division

% Modulo Division

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Arithmetic Expression Let int x = 15; int y = 6;int z;Example:

z = x+yz = x-y

z = x*yz = x/y (decimal part truncated)z = x%y (remainder of the division)

Q. If x and y are declared as float then?Q. If x is integer and y is float then?

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Example 2 :Program to compute area and circumference of acircle

#include #define PI 3.14

int main(void){

int radius;float area,circum;

printf("Enter radius of a circle\n");scanf("%d", &radius);

area = PI * radius * radius;circum = 2 * PI * radius; printf("Area = %f \t Circumference =

%f ",area, circum);return(0);

}

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Precedence & Associativity of

Arithmetic OperatorsOperator Precedence Associativity

() 1 Left to Right

Unary +, - 2 Left to Right

*, /, % 3 Left to Right

+, - 4 Left to Right

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Assignment Operators

Simple AssignmentOperatorsa = a+1a = a-1a =a*(b+1)a = a/(b+1)a = a%b

Shorthand Operators a+= 1

a-= 1a*=b+1a/=b+1

a%=b

Short hand statement is more conciseand easier to read

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Example

Let int x, a, b, c;

1. x = a b / 3 + c * 2 12. x = ( (a * b) + (-b / c * a) ) / c3. x = (a c / 5 + b) % 100 + 26

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Type Conversion

Implicit Type ConversionExplicit Type Conversion

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Implicit Type Conversion

C automatically converts anyintermediate values to the proper data

typeLower type is automatically converted tothe higher type before operationproceeds

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Implicit Type Conversion

int i, x;float f;

double d;long int l;

x = l / i + i * f - d;

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Explicit Type Conversion

Also called Type castingExplicit conversion of the data type of some variable or expression locally.Syntax

(type-name) expressionE.g

int female_no, male_no;float ratio;ratio = (float) female_number /male_number;

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More Examples on type

castingExample ResultX = (int)7.5 X = 7

A = (int)21.3/(int)4.5 A = 5

B = (double)sum/n Results is in double

Y = (int)a+b A is converted to int andthen added to b

Y = (int)(a+b) Result of a+b isconverted to int

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Final result of an expression is converted to thetype of variable on the left of the assignment =before assigning result to it.

float to int truncation of fractional part.double to float rounding of digitslong int to int dropping of excess higher order bits

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More Examples:

Write a equivalent C expression for given algebraic expressions.

1. (a+b)(c+d)2. ax 2+bx+c3. p r 2 +2 p rh

4. s = ut + 1/2at2

5. T = (m1m2/m1+m2)

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Relational OperatorsOperator Meaning

< Is less than

Is greater than

>= Is greater than or equal to

== Is equal to

!= Is not equal to

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Examples:

5 = 0 FALSE

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Logical Operators

Operator Meaning

&& Logical AND

|| Logical OR

! Logical NOT

Q. Are !(a>b) and a

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Exercise 1. Write a program which takes marks of five

students as input and computes the averagemarks. Print the average mark of five students.

2. Write a program to compute roots of a quadraticequation

ax 2 + bx + c = 0

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Exercise

3 . Write a program to solve two linear equations

2x + 8y 10 = 05x + 6y 5 = 0

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Increment and DecrementOperators

++ Adds one to the operand-- Subtracts one from the operandBoth are unary operators

++i is equivalent to: i = i+1--i is equivalent to: i = i-1

Is ++i and i++ are same??

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What are Postfix and Prefix Expressions?

In postfix, the expression is evaluated first using the originalvalue of the variable and then the variable is incremented (or decremented) by one.

Ex. m = n++; or m = n--;

In prefix, the variable is incremented (or decremented) firstand then the expression is evaluated using the new value of the variable.

Ex. m = --n; or m = ++n;

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Postfix and Prefix Examples

j =10;

i =j++;What is the values of i and j?

j =10;i=--j;

What is the values of i and j?

Output

i = 10 j = 11

Outputi = 9 j = 9

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Conditional Operator

Also called Ternary operator Syntax

Variable = expression1 ? expression2

: expression3

Example:

a=5; b=10;

x =(a>b) ? a : b; What will be the value of x??

Output

X = 10

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Bitwise Operators

Manipulation of data at bit levelNot be applied to float or double values

Operator Meaning

& Bitwise AND

| Bitwise OR

^ Bitwise exclusive OR

> Shift right

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Special Operators

The Sizeof Operator Returns the number of bytes the operandoccupies

Examples: p=sizeof(value);

q=sizeof(float);

r=sizeof(long int);

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Comma Operator

Used to link the related expressionstogether.

Evaluation starts from left to right. And the value of the right mostexpression is the value of thecombined expression.Example:

1. value = (a = 6, b = 7, c = 8,a+b+c);

Value contains 21

Operators Associativity Rank

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(),[] L to R 1

+, -, ++, --, !, ~, *, &, sizeof,(type)

R to L 2

*, /, % L to R 3Binary plus(+) and Binary minus (-) L to R 4

L to R 5

= L to R 6

==, != L to R 7

& L to R 8

^ L to R 9

| L to R 10

&& L to R 11

|| L to R 12

?: R to L 13

=, *=, /=, %=, +=, -=, &=, ^= R to L 14

, L to R 15

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Algorithms An Algorithm is just a detailed sequence of simple stepsthat are needed to solve a problem

Flow ChartsFlow Charts are maps or graphical representations of aprocess.Steps in a process are shown with symbolic shapes, and

the flow of the process is indicated with arrowsconnecting the symbols

ALGORITHMS AND FLOW CHARTS

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Symbols in Flowchart

START , END

INPUT

PROCESS INPUT DATA

DECISION

CONNECTOR

CONNECTOR

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Example Flow Chart

Marks = 50Avg = 45

Marks > avg

END

START

YES

NO

Flow chart to find

whether the the marks of a student is above avg or below avg

Print below Avg

Print above Avg

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Any Doubts or Questions?