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Function Introduction

Function Introduction . Lesson xx. Objectives. Why use functions Program that needs a function Function header Function body Program rewritten using a function. Why Use Functions. Functions allow you to repeat a body of code without having to physically rewrite it many times .

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Function Introduction

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  1. Function Introduction Lesson xx

  2. Objectives Why use functions Program that needs a function Function header Function body Program rewritten using a function

  3. Why Use Functions • Functions allow you to repeat a body of code without having to physically rewrite it many times. • Functions allow you to modularize code. This means that you can break down your problems into small blocks and each block can be put into a function. This makes a program easier to work with and debug. • Functions allow many people to work on one program at the same time. Each person writes a different function.

  4. Program Definition Write a program that: • Prints a row of 45 ‘*’s • Prints the contents of the variable a • Prints a row of 45 ‘*’s • Prints the contents of the variable b • Prints a row of 45 ‘*’s • Prints the contents of the variable c • Prints 2 rows of 45 ‘*’s

  5. Program Output

  6. Program Listing #include "stdafx.h" #include <iostream> using std::cout; using std::endl; int main() { int a = 5, i; float b = 17.345; char c = 'q'; cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; cout << " a = " << a; /************************************************/ cout << endl ; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; cout << " b = " << b; /************************************************/ cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; cout << " c = " << c; /************************************************/ cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; system ("pause"); return 0; }

  7. cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; cout << " a = " << a; Code to Print 45 ‘*’s & Variable a (1) (2) (3) (4)

  8. cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; cout << " b = " << b; Code to Print 45 ‘*’s & Variable b

  9. cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; Code to Print 45 ‘*’s

  10. void funName ( ) ///function header { Body of code } Function Setup

  11. Function Header void funName( ) Function name Return type Argument list

  12. Program Rewritten Using Functions #include "stdafx.h" #include <iostream> using std::cout; using std::endl; void prtStar ( ); ///function prototype int main() { int a = 5,; float b = 17.345; char c = 'q'; prtStar ( ); cout << " a = " << a; /************************************************/ prtStar (); cout << " b = " << b; /************************************************/ prtStar (); cout << " c = " << c; /************************************************/ prtStar (); prtStar (); return 0; } void prtStar ( ) { int i; cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; }

  13. Function prtStar ( ) void prtStar ( ) { int i; cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; }

  14. Variable Declaration in prtStar ( ) void prtStar ( ) { int i; cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; }

  15. Function prtStar ( ) void prtStar ( ) { int i; cout << endl; for (i = 0; i < 45; i++) { cout << "*"; } cout << endl; }

  16. Function Prototype / Declaration #include "stdafx.h" #include <iostream> using std::cout; using std::endl; void prtStar ( ); ///function prototype int main() { int a = 5,; float b = 17.345; char c = 'q'; prtStar ( ); cout << " a = " << a; /************************************************/ prtStar (); cout << " b = " << b; /************************************************/ prtStar (); cout << " c = " << c; /************************************************/ prtStar (); prtStar (); return 0; }

  17. Function Call / Invocation #include "stdafx.h" #include <iostream> using std::cout; using std::endl; void prtStar ( ); ///function prototype int main() { int a = 5,; float b = 17.345; char c = 'q'; prtStar ( ); cout << " a = " << a; /************************************************/ prtStar (); cout << " b = " << b; /************************************************/ prtStar (); cout << " c = " << c; /************************************************/ prtStar (); prtStar (); return 0; }

  18. Function Review How to write a function function header { // body } void fun ( ) { //code goes here } How to call a function 1. function prototype / declaration 2. function call / invocation void fun ( ) ; ///function declaration void main ( ) { . . . fun ( ) ; ///function call . . . return 0; }

  19. Summary Why use functions Program that needs a function Function header Function body Program rewritten using a function

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