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FUNCTIONS
A function groups a number of program
statements into a unit and gives it a name. This
unit can then be invoked from other parts of the
program.
The most important reason to use functions is
to aid in the conceptual organization of a
program.
FUNCTIONS
Another reason to use functions (and the
reason they were invented, long ago) is to
reduce program size. Any sequence of
instructions that appears in a program more
than once is a candidate for being made into a
function. The function’s code is stored in only
one place in memory, even though the function
is executed many times in the course of the
program.
#include //for cout, etc. void star_line(void); using namespace std; int main() { star_line(); cout<<”Wellcome to My Program”<<endl; star_line(); return 0; } void star_line(void) { for(int i = 0; i < 45 ; i++) cout<<”*”; cout<<endl; }
FUNCTIONS
Function contains three parts
The Function Declaration
Just as you can’t use a variable without first
telling the compiler what it is, you also can’t use
a function without telling the compiler about it.
e.g void star_line(void);
Calling the Function
all we need to call the function is the function
name, followed by parentheses and a
semicolon.
e.g star_line();
FUNCTIONS
Void my_func(void);
Int my_func(void);
Void my_func(int , float);
Float my_func(int , char);
#include //for cout, etc. void star_line(char , int); using namespace std; int main() { star_line('-',45); cout<<”Wellcome to My Program”<<endl; star_line('*',23); return 0; } void star_line(char ch , int count) { for(int i = 0; i < count ; i++) cout<<ch; cout<<endl; }
RETURNING a Value
When a function completes its execution, it can
return a single value to the calling program.
Usually this return value consists of an answer
to the problem the function has solved. The
next example demonstrates a function that
returns a weight in kilograms after being given
a weight in pounds.
#include //for cout, etc. float lbs_to_kg(float); using namespace std; int main() { float lbs , kg; cout<<”Enter your weight in pounds : ”; cin>>lbs; kg = lbs_to_kg(lbs); cout<<”Your Weight in Kilograms is : “<<kg<<endl; return 0; } float lbs_to_kg(float pounds) { int kilogram; kilogram = 0.453592 * pounds; return kilogram; } docsity.com
LAB TASK 1
Write a function called circarea() that finds the
area of a circle in a similar way. It should take
an argument of type float and return an
argument of the same type. Write a main()
function that gets a radius value from the user,
calls circarea(), and displays the result.
LAB TASK 2
Raising a number n to a power p is the same as
multiplying n by itself p times. Write a function
called power() that takes a double value for n
and an int value for p, and returns the result as
a double value.
LAB TASK 4
Write a function called hms_to_secs() that
takes three int values—for hours, minutes, and
seconds—as arguments, and returns the
equivalent time in seconds (type long). Create a
program that exercises this function by
repeatedly obtaining a time value in hours,
minutes, and seconds from the user (format
12:59:59), calling the function, and displaying
the value of seconds it returns.
