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TA ZC142 Computer ProgrammingLecture 9

Date: 06/01/2013

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Last Lecture

Sorting TechniquesInsert an element into a Sorted Array

Remove an element from a Sorted ArrayEnumerated data typesIntroduction to user defined data types

Structures Union

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Todays Agenda

Problem Solving Technique Top Down Design

Functions

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Content

User-Defined FunctionsFunctions with no arguments and no returnvalueFunctions with arguments and no return valueFunctions with arguments and return valueFunctions with no arguments but returns a value

Passing Array as an argument to a functionOne dimensionalStrings

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Top-down Design

How do you solve the sub-problem?Divide-and-conquer again!

Steps1. Divide the problem into sub-problems2. Repeat step 1 for each sub-problem

until the problem is small enough to have anatomic solution.3. Combine the solutions.

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User-Defined Functions

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Functions

A function is a named, independentsection of C code that performs a specifictask and optionally returns a value to thecalling program/function.

A C program consists of one or morefunction definitions, including exactly onethat must be called main().

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Function Declaration and Definition

A declaration merely provides a function prototype .

It includes the return type and the list of parameters.Syntax:return_type function_name ( arg-typ name-1 ,..., arg-typ

name-n );

Example:int hex(int val);

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Function Parameters

There are two types of function parameters:Formal parameters:

Appear in a declaration or a definition of a function.

Actual parameters: Appear in a call to the function.

Examples:int f(int x); here x is a formal parameter

i = f(3); here 3 is the actual parameter corresponding to the formal

parameter .

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Complete C Program Using Function

long int cube(int); /* Function declaration */int main(){ long int c;

c = cube(5) ; /* Function call */printf(Cube of 5 = %ld,c);

return;} /* Function definition starts from here */long int cube(int num){ long int cb; /*Local variable declaration */

cb = num*num*num;return cb; /* Return value */

}

Actual parameter

Formal parameter

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What will be the output???

int Addnum(int, int);int main(){ int a = 10,b = 20;

printf("%d %d %d",a,b, Addnum(a,b) );

return;}int Addnum(int a, int b){ int c;

c = a+b;return c;

}

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Functions with no arguments and no returnvalue

void displayline(void);void sum(void);void main(){ displayline();

sum();}

void displayline(){ int j;

for(j=0;j

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Functions with arguments and no return valuevoid displayline(char);void Sum(float, float);void main(){ char ch;

float a,b; printf (Enter character to print in line \ n);

scanf (%c,&ch );displayline(ch);

printf (Enter value of a and b \ n); scanf (%f %f,&a,&b );Sum(a,b);

}

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Functions Definition

void displayline(char ch){ int j;

for(j=0;j

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Functions with arguments and return value

int Add(int, int);int Sub(int, int);int Div(int, int); /* Function Prototype */int main(){ int x,y;

printf (Enter two values: \ n); scanf (%d %d,&x,&y );

printf (Sum =%d, Add(x,y ) ); /*Function Call*/ printf (Subtraction = %d, Sub(x,y) ); printf (Division = %d, Div(x,y) );

return;}

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Function Definition

int Add(int a,int b)

{return(a+b);

}int Sub(int a,int b){

return(a-b);}

int Div(int a,int b){

return(a/b);}

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int fact(int );int main(){

int n=5; printf("factorial of %d = %d",n,fact(n));

}int fact(int n)

{int f=1,i=2;

while(i

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No arguments but returns a value

int ReadNumber(void);

void main(){ int num = ReadNumber();

printf (%d,num );

}int ReadNumber(void)

{ int number;

scanf (%d,&number );return(number);

}Example: getchar()

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Compute sine series :x x 3 /3! + x 5 /5! - ..n terms

Write a function power(x,a) and fact(a).

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Compute the roots of quadraticequation.

ax 2 + bx + c = 0 Write a function

quad(a,b,c,sign) tofind roots of a quadratic

equation and call thisfunction in main().

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float quad(int a,int b,int c,int sign);int main(){

int a,b,c; float root1,root2; int flag=0;while(!flag){

printf("enter a,b,c \n");scanf("%d %d %d",&a,&b,&c);

if((b*b)>(4*a*c) && a != 0)break;

elseprintf("Invalid entries\n");

}root1 = quad(a,b,c,1);root2 = quad(a,b,c,0);printf("root1 = %f root2 = %f\n",root1,root2);

}

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float quad(int a,int b,int c,int sign){

float disc,r;

disc = b*b - 4*a*c;if(sign ){

r =(-b + sqrt(disc))/(2*a);return(r);

}else{

r =(-b - sqrt(disc))/(2*a);

return(r);}

}

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Passing Arrays To Functions (Pass by reference)

One- dimensional Array:int Maximum(int a[], int size);

main(){ int val[5]={3,5,2,7,4};

printf (%d \ n,Maximum (val,5));}int Maximum(int a[], int size)

{ int i, max = a[0];for(i=0; i

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Rules to pass an Array to a function

1. The function must be called by passing name of the array.

2. In the function definition, the formal parameter must be an array type; the size of the array doesnot need to be specified.

3. The function prototype must show that theargument is an array.

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Write a program using functions to sortelements in an 1D array. Write a functionto read an array, print an array and sort anarray.

Extend the above program by adding fewmore functions to search an element in anarray, find maximum in an array, find sum

of elements in an array and return thesum. return the results found in eachfunction to the calling function.

void readArr(int a[] int size);

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void readArr(int a[],int size);void printArr(int a[],int size);void sortArr(int a[],int size);

int main(){

int a[5]; printf("Enter elements in an array\n");

readArr(a,5); printf("Display elements in Array before

sorting\n"); printArr(a,5);

sortArr(a,5); printf("Display elements in Array after

sorting\n"); printArr(a,5);

}

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Write a function to calculate the grosssalary of a employee if his basic salary isinput through the keyboard. if basicsalary is less than Rs.1500 then HRA =Rs. 500 and DA = 90% of basic. If salaryis equal or greater than 1500 then HRA =10% and DA = 95% of basic salary. Basic

salary is passed to the function and gssalary is returned.

Programming Exercise

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Any Doubts ?