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TA ZC142 Computer ProgrammingLecture 5Date: 23/01/2013

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Last Lecture

Switch case statementRepetition Control Structure for statement while statement do-while statement

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Todays Agenda

Continue loops Do-While Loop

Arrays Derived Data Types 1-D Array 2-D Array Memory organization Programming Exercises

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Control Structure

Sequential Control Structure It s a sequential flow of execution of

instructions.Selection Control Structure

This control structure chooses amongalternative program statements.

Repetition Control Structure This control structure repeats a group of

program statements till it satisfies somecondition.

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Basics of loops1. Initialization of a condition variable.2. Execution of the loop statements.3. Test for a specified value of the condition

variable.

4. Updating the condition variable.5. C provides three constructs for loop

operations

6. The for statement7. The while statement8. The do while statement

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While

while (test){

loop_body;}

test

loop_body

T

F

Loop body can contain block of statements.Executes loop body as long as test evaluates to TRUE (non-zero).

Note: Test is evaluated b e f o r e executing loop body .

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Introducing while loop

sum = 0;for (i = 1; i

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While loop example

x = 0;while (x < 10){

printf(%d , x); x = x + 1;

}

char c = Y ;

while( c == Y )

{

printf(Inside Loop \n);

printf(Do you want to continue inside loop? (Y/N));

c = getchar();

}

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Infinite Loops

The following loop will never terminate:Why??? x = 0;

while (x < 10)

printf(%d , x);

Loop body does not change condition, so

test never fails.

This is a common programming error thatcan be difficult to find.

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Nested LoopsThe statement of for is again a for statementLoop body can (of course) be another loop.

/* print a multiplication table */for (m1 = 1; m1

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int main()

{int n = 100; // number int i, prime = TRUE;

for(j=2;j

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ArraysDerived Data Type

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Arrays

An array is fixed size sequenced collection of elements of the same data type addressableby index or subscript.

It can be used to represent a list of homogenous values

Examples:List of marks of studentsList of employee id no.s in an organization

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One Dimensional Arrays

List of items given one variable name using

only one subscriptDeclaration: type variable_name[size];

Here size indicates the maximum number of elementsThe subscript value start from 0 to s ize-1 Example:

int number[10];float number[10];char grade[10];

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Compile time initializationint num[5]={0,0,0,0,0};

float num[5]={0.0,10.5,11,-13.25};int num[]={1,2,3,4,5}; is it correct?

Consider the following initializationint num[4]={10,20,30,40,50};

Initialization

Invalid Statement

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Run time initialization

for(i=0; i

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#include#include#define N 10

int main() {float marks[N],sum,ave;int count,no;printf("enter size of array\n");scanf("%d",&no);if(no > N) {printf("size of array entered by you is exceeding the maximum

size\n");exit(0);

}for(sum=0.0,count=0;count

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/* Calculate and display the deviation */ for(i=0;i

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Problems with arrays!!!- No Bound Checking!!!

There is no check in C compiler to see if the subscript used for an array exceedsthe size of the array.Data entered with a subscript exceedingthe array size will

simply be placed in memory outside thearray limit and

lead to unpredictable results. It s a programmers responsibility to take care.

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Exercise on Arrays

Write a program to find a number in aninteger array. Also find the number of timesit occurs in the array.

Write a program to find maximum in anarray. Also print the index at which it occurs.

Write a program copy the elements of onearray into another array in reverse order.

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Exercise on Arrays

Write a program to count the number of students belonging to each of the following

groups of marks: 0-9,10-19,20- 29,..,90 -91,100. Assume there are 50 students.Declare an array to store the frequency of

marks in each group.

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Do while loop

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Do-While

do{

loop_body;}while (test);

loop_body

testT

F

Loop body can contain block of statements.Executes loop body as long as test evaluates to TRUE (non-zero).

Note: Test is evaluated af ter executing loop body.

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int i = 1,sum = 0;

do{

sum = sum + i;i = i+2;printf(%d %d \ n,i,sum);

} while(sum < 40 || i < 10);printf(%d %d \ n,i,sum);

OUTPUT

i sum

3 1

5 47 9

9 16

1125

11 25

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Write a program to find total marks in5 subjects for 50 students. Find the

average marks. Find the number of students above average ,belowaverage and at average. Find the

maximum total marks. Use arrays.

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Write a program to copy the elements of onearray into another array in reverse order.

Write a program to count the number of students belonging to each of the followinggroups of marks: 0-9,10-19,20- 29,..,90 -91,100. Assume there are 50 students.Declare an array to store the frequency of marks in each group.

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Write a multiplication tablefrom (1 X 1) to (10 X 10) usingdo-while loop.

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int main(){ int m1,m2,product;

m2 = 1;do {

m1 = 1;do {

product = m1 * m2; printf("%d X %d = %d\n",m2,m1,product); m1 = m1 + 1;} while(m1

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Continue statement

continue;sum = 0;for(i=0;i

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Two Dimension Array

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Two dimensional arrays also called as matrixDeclaration :

type variable_name[size1][size2];

size1 >Number of rows in matrix

size2 > Number of columns in matrix Examples :

int number[4][3]; /* 12 elements */float number[3][2]; /* 6 elements */char name[10][20]; /* 200 chars */

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Initialization of a 2-D Arrayint a[2][3]={1,2,3,4,5,6};int a[2][3]={{1,2,3}, {4,5,6}};int a[][3]={{1,2,3}, {4,5,6}} ;

How values will be assigned in each case??Following initializations are not allowedint a[3][]={2,4,6,8,10,12};int a[][]={2,4,6,8,10,12};

Note: If the first bracket pair is empty, thencompiler take the size from the number of inner

brace pairs

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Memory Map for 2-D Arrays

Kept in memory as a linear sequence of variables.

Two methods for storing- Row major Column major Example: int a[3][3];Row major storage:a[0][0], a[0][1], a[0][2], a[1][0], a[1][1], a[1][2],a[2][0], a[2][1], a[2][2]

Column major storage:a[0][0], a[1][0], a[2][0], a[0][1], a[1][1], a[2][1],a[0][2], a[1][2], a[2][2]

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Accessing Two Dimensional Array

int a[3][4]={1,2,3,4,5,6,7,8,9,10,11,12};for(i=0;i

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Working with two dimensional Arrays

Matrix Addition and Subtraction

Let A[m][n] and B[p][q] are two matrices.Precondition : m equals to p and n equals to q

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Matrix Addition

Algorithm Steps: 1. Read two matrices A and B and

initialize C matrix to zero2. Repeat (3) for i=0 to m-13. Repeat (3.a) for j=0 to n-1

3.a) C[i][j] = A[i][j] +B[i][j]4. Display C matrix.

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Write a program to find total marks of 5students in 3 subjects and store the totalmarks of each student in a onedimensional array. Also find the highest

marks in each subject and store in anotherarray.

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Matrix Multiplication:

M1xM2

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Pre condition: Number of columns in M1 should beequal to number of rows in M2

Algorithm Steps: 1. Read two matrices M1[m][n] and M2[n][r] andinitialize another matrix M3[m][r] for storing result.

2. Repeat for i=0 to m-13. Repeat for j=0 to r-14. M3[i][j] = 0 5. Repeat for k=0 to n-16. M3[i][j] += M1[i][k] * M2[k][j]7. 3. Print matrix M3.

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Write a program to read a matrix of characters. Dimensions are taken fromthe user.(a) Convert a lower case alphabet intoupper case alphabet.if there is a character other thanalphabet replace that character with

$ . Display the final matrix with all theupper case alphabets and $.

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(b) Find the vowels inthe resultant

matrix. Printnumber of vowelsin each row. Alsoprint the vowel

along with its index.

a f # T @

i s ! o m

V 5 u Q i

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Any Doubts orQuestions?