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# Unit2 jwfiles

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### Unit2 jwfiles

1. 1. Modularizing and Reusing of code through FunctionsCalculation of area of Circle is separated into a separate module from Calculation of area ofRing and the same module can be reused for multiple times. /* program to find area of a ring /* program to find area of a ring */ */ #include<stdio.h> #include<stdio.h> float area(); Function Declaration int main() Repeated & Reusable int main() { blocks of code { float a1,a2,a,r1,r2; float a1,a2,a; a1 = area(); Function Calls printf("Enter the radius : "); a2 = area(); scanf("%f",&r1); a = a1- a2; a1 = 3.14*r1*r1; printf("Area of Ring : %.3fn", a); printf("Enter the radius : "); } scanf("%f",&r2); float area() Function Definition a2 = 3.14*r2*r2; { a = a1- a2; float r; printf("Area of Ring : %.3fn", printf("Enter the radius : "); scanf("%f", &r); a); return (3.14*r*r); } }
2. 2. A Function is an independent, reusable module of statements, that specified by a name. This module (sub program) can be called by it’s name to do a specific task. We can call the function, for any number of times and from anywhere in the program. The purpose of a function is to receive zero or more pieces of data, operate on them, and return at most one piece of data. A Called Function receives control from a Calling Function. When the called function completes its task, it returns control to the calling function. It may or may not return a value to the caller. The function main() is called by the operating system; main() calls other functions. When main() is complete, control returns to the operating system. value of ‘p’ is copied to loan’ value of ‘n’ is copied to terms’int main() { value of ‘r’ is copied to ‘iRate’ int n; float p, r, si; printf(“Enter Details of Loan1:“); float calcInterest(float loan , int terms , float iRate ) { scanf( “%f %d %f”, &p, &n, &r); float interest; The block is si =calcInterest( p, n , r ); interest = ( loan * terms * iRate )/100; executed printf(“Interest : Rs. %f”, si); return ( interest ); printf(“Enter Details of Loan2:“); }} Called Function value of ‘interest’ is assigned to ‘si ’ Calling Function Process of Execution for a Function Call
3. 3. int main() { int n1, n2; printf("Enter a number : "); scanf("%d",&n1); printOctal(n1); readPrintHexa(); printf("Enter a number : "); scanf("%d",&n2); 1 2 printOctal(n2); printf(“n”); } 3 7 Flow of 8 void printOctal(int n) Control { printf("Number in octal form : %o n", n); in } Multi-Function6 void readPrintHexa() Program { int num; printf("Enter a number : "); scanf("%d",&num); printHexa(num); printf(“n”); } 4 void printHexa(int n) 5 { printf("Number in Hexa-Decimal form : %x n",n); }
4. 4. /* Program demonstrates function calls */ Function-It’s Terminology#include<stdio.h>int add ( int n1, int n2 ) ; Function Nameint main(void){ Declaration (proto type) of Function int a, b, sum; printf(“Enter two integers : ”); Formal Parameters scanf(“%d %d”, &a, &b); Function Call sum = add ( a , b ) ; printf(“%d + %d = %dn”, a, b, sum); return 0; Actual Arguments} Return Type/* adds two numbers and return the sum */ Definition of Functionint add ( int x , int y ){ Parameter List used in the Function int s; s = x + y; Return statement of the Function return ( s );} Return Value
5. 5. Categories of Functions/* using different functions */ void printMyLine() Function with No parametersint main() { and No return value int i;{ for(i=1; i<=35;i++) printf(“%c”, ‘-’); float radius, area; printf(“n”); printMyLine(); } printf(“ntUsage of functionsn”); printYourLine(‘-’,35); void printYourLine(char ch, int n) radius = readRadius(); { Function with parameters area = calcArea ( radius ); and No return value printf(“Area of Circle = %f”, int i; for(i=1; i<=n ;i++) printf(“%c”, ch);area); printf(“n”);} } float calcArea(float r) float readRadius() Function with return { Function with return { value & No parameters float r; float a; value and parameters printf(“Enter the radius : “); a = 3.14 * r * r ; scanf(“%f”, &r); return ( a ) ; return ( r ); } } Note: ‘void’ means “Containing nothing”