functions intro to computer programming

7/23/2019 Functions Intro to Computer Programming

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also called subroutines, subprograms

allow complicated programs to be divided

into small blocks divide and conquer

a named sequence of statements thatperforms some useful procedure

is a complete and independent program


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A Function must have:

1. Return type (void if function does not return anything)

2. Name followed by a pair of ()

3. Names follow rules in writing identifiers

4. 0 or more parameters to be placed inside the pair of ()

What is a parameter? - A parameter is a local variable. It has a data typeand a name. It is a special kind of variable that refers to data that asubroutine receives on which to operate

5. Pair of curly braces {} (inside the brackets is the function body)

6. A return value


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Function Syntax:

functionName( )

{

return ;

}

Note that:

If return-type is omitted, C defaults to int. The return-value mustbe of the declared return-type.

functionName follows rules in writing identifiers and is used incalling the function

To use a function, simply call it using the functionName


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A Function may belong to any of the followingtypes:

1. Functions with no parameter and no return

type

2. Functions with parameters and no returntype

3. Functions with parameters and return types


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Function with no parameter and no return type

void drawSquare()

{

// prints a 3x3 square

printf(***\n);

printf(***\n);printf(***\n);

}

Note that:

Function has no return type it is VOID. Function Name is drawSquare No Parameters drawSquare prints / displays a 3x3 square


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Code A: Without usingFunctions

main()

{

printf(***\n);printf(***\n);

printf(***\n);

}

Code B: Using Functions

void drawSquare()

{

// prints a 3x3

squareprintf(***\n);

printf(***\n);

printf(***\n);

}

int main(){

drawSquare();

return 0;

}


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Looking at the comparison you can observethat:

Code A and Code B produces the same output

Code B has 2 functions namely main() and

drawSquare()

Code B uses a function (drawSquare()) toprint the 3 x 3 square


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Functions with parameters and no return type

void addition(int a, int b)

{

// compute for the sum of a & b

int sum;

sum = a + b;

printf(The sum of is %d, sum);

}

Note that:

Function has no return type it is VOID. Function Name is addition Two Parameters a and b both of the type int addition will display the sum of two integers


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Functions with parameters and return type

int addition(int a, int b)

{


int sum;

sum = a + b;

return sum;

}

Note that:

Function has no return type int. Function Name is addition Two Parameters a and b both of the type int addition will return the sum of two integers


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CODE A: Function with parameters andno return type

void addition(int a,int b)

{


int sum;

sum = a + b;

printf(The sum of is %d,

sum);

}

int main()

{

int x = 5 , y = 3;

addition(x, y);return 0;

}

CODE B: Function with parameters andreturn type

int addition(int a,int b)

{


int sum;

sum = a + b;

return sum;

}

int main()

{

int sum, x = 5 , y = 3;

sum = addition(x, y);printf(The sum of is %d, sum);

return 0;

}


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Parameters vs Arguments

int addition(int a,int b)

{


int sum;

sum = a + b;

return sum;

}

int main()

{

int sum, a = 5 , b = 3;

sum = addition(a, b);

printf(The sum of is %d, sum);return 0;

}

Here a & b are calledparameters

Here a & b are called

arguments

So whats the difference?


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Parameter

A piece of information you provide in order to

call a function.

Parameters are like variables in the sense that

they contain values and have types

rgument

A value that you provide when you call a

function. This value must have the same type as the

corresponding parameter.


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functions intro to computer programming

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