Function Part 1 PDF

Learning Outcomes Modular Programming  Complex problems can be broken down into sub tasks, each of...

Learning Outcomes Modular Programming  Complex problems can be broken down into sub tasks, each of which is easy to implement in C++. At the end of this lecture, you should be able to:  Modular programming: breaking a program up into smaller,  explain the benefits of modular programming manageable functions or modules. Function  describe the concept of a function  Function: a block of statements in a program to perform a specific task.  identify types of function Part 1  define function, declare function and call function  Motivation for modular programming: Multiple programmers : each sub task, is easy to be implemented  use actual parameter and formal parameter by a programmer.  differentiate function that returns a value and Easier readability, testing and maintenance : program is read, function that does not return a value tested and maintained based on its specific function.  identify local and global variables and their scope Reduce duplication of code : functions can be called/used repeatedly in a program, simplifies the process of writing programs. 2 LECTURE 6 3 LECTURE 6 4 LECTURE 6 Function Concept Function Concept Types of Function Functions in a C++ program A function is to :  There are 2 types of function : ✓ receive zero or more data Standard Library (or Pre-defined) Function Programmer defined Function ✓ operate on the data; or just produce side effect (output); or both  In C++, a program contains numerous functions : ✓ return at most one data value. main() : is a programmer defined function; it is a must and Function definition: statements in program that describe can only be one in a program. how a function will do its task. main() often call/use standard library functions. Function call: statement in program that causes a function main() can also call/use other programmer defined to execute, in order to get its task done. functions. A programmer defined function, can also call other programmer defined functions. 5 LECTURE 6 6 LECTURE 6 7 LECTURE 6 8 LECTURE 6 Standard library / Pre-defined function Standard Library Function Standard Library Function Some functions defined in : Pre-defined Functions – Program eg.  Example : some of the pre-defined mathematical Function Explanation Example #include  Its function definition has been coded and kept in a file functions in are: log( x ) Natural logarithm of x (base log( 2.718282 ) is 1.0 #include called header file. of e) ✓ The power function, pow(x,y) using namespace std;  Programmer just need to know: ✓ The square root function, sqrt(x) log10( x ) Logarithm for x (based of 10) log10( 100.0 ) is 2.0 int main() ✓ what the pre-defined function will do, ✓ The floor function, floor(x) pow( x, y ) x raised to the power y pow(2.0,7) is 128 { pow(9, 0.5) is 3 double angle; ✓ how to call it,  To make use of the function, programmer has to include the sin( x ) Trigonometric value of sine sin(0.0) is 0 cout > angle; example : #include sqrt( x ) Non-negative square root of x sqrt(400.00) is 20.0 cout