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CHAPTER 5FUNCTIONS
Predefined functions
Independent Functions
Functions data type
Functions with parameter
Value
Reference
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a mini-program containing algorithms to do a
specific task
a function could be invoked (called) many timesthrough its name (to execute its task), by the
main function or other functions
when a function is invoked, the computer will
execute all the instructions in the function from
start to end, and then it goes to the instruction
after the function call
What is a Function?
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2 types of functions :-
1. Predefined function or built-in or library
function2. Independent function or user-defined function
Function Classification
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PREDEFINED FUNCTION
Functions that are ready-made by the producer of a compiler
and stored in the header files (.h) called libraries
To use the predefined function, the appropriate library file must
be included in the preprocessor directive (# include)Common header files are :-
a) iostream.h b) iomanip.h c) string.h
d) char.h e) math.h f) stdlib.h
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Independent Function
functions written by the programmer
the way the functions are used (called) is the same
as library functions
to use a function, only the prototype and adescription on what the function does is sufficient
3 requirements to use the independent function :-
a) Function prototype declaration
b) Function callc) Function definition
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Types of Functions1. Function with no return value and no parameter
Function Prototype Function Call Function Definition
void display(); { .
..
display();
..
}
void display()
{
cout radius;
area = radius * radius * 3.142;
cout
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2. Function with no return value and has a parameter
Function Prototype Function Call Function Definition
void average(int, int); { int x, y;
cin >> x >> y;
average(x, y);..
}
void average(int a, int b)
{ int avg;
avg = (a + b)/2
;cout
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3. Function with return value and no parameter
Function Prototype Function Call Function Definition
float areaCircle(); { double area;
area =
areaCircle();
cout radius;A = 3.142 * radius * radius;
return A;
}
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4. Function with return value and has a parameter
Function Prototype Function Call Function Definition
int factorial(int); { int x, fac;
cin >> x;
fac = factorial(x);cout 0){ result = result * a;
a = a 1;
}
return result;
}
int average(int, int); { int x, y;
cin >> x >>y;
cout
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Function Prototype Function Call Function Definition
void swap(int &, int
&);
{ int x, y;
cin >> x >>y;
swap(x, y);
}
void swap(int &a, int &b)
{ int temp;
temp = a;
a = b;
b = temp;}
void calc(int, int, int
&, float &);
{ int x, y, total;
float avg;
cin >> x >>y;
calc(x, y, total,
avg);
}
void calc(int a, int b, int &jum, float &purata)
{
jum = a + b;
purata = jum/2;
}
5. Function with return value and has a reference
parameter reference parameter used to return values as a return output to
called function.
it is used where more than one value or variable need to be returned to
the called function.