Coded in TurboC
in easy steps.
by “Md. Farrukh Asif”
Dear viewers, you will learn
in detail about
“Functions and its type”
in C/C++.
This topic will cover about the “Functions”. Details are below:
|
·
What is Function? |
|
·
How to Define a Function? |
|
·
What is the Built-in / Library Function? |
|
·
What is User Defined Function? |
|
·
What is Void Function? |
|
·
What is Called by value Function? |
|
·
What is Call by Reference Function? |
|
·
What are Multi-call by value/reference Functions? |
|
·
What are Multi File (separate file) Functions? |
C Language:
C Language:
C for the
beginner 's by Md Farrukh Asif
Operators
in C by Md. Farrukh Asif
C's
Control Flow by Md. Farrukh Asif
String handling in C by Md Farrukh Asif
The
Function of C Language by Md. Farrukh Asif
File Handling
with various statements/syntaxes in Programming and their output in C Language.
C
for beginner's programming with output. Course Code – 106 [‘C’]) TMBU,BGP
BCA
SOLVED EXAMINATION QUESTIONS WITH ANSWERS Course Code – 106 [‘C’]) TMBU,BGP
Now come to the “Topic”….
A function is a self-contained program segment
that carries out some specific, well-defined task.
· How to define
a Function?
A function definition has three
principal components.
a. The First
Line.
b. The
Argument declared.
c. The Body of
the function.
We can define a function using data type. Like void, int, float, char, etc…
The first line of a function definition contains the type
specification of the value returned by the function, followed by the function
name, and (optional) a set of arguments, separated by a comma and enclosed in
parenthesis.
In general terms, the first line can be written as,
Data-Type Name_of_Function(format argument 1, format argument
2, format argument 3,…… format argument
n)
Where the data type represents the data type of the value
that is returned and the name represents the function name that can be defined by
the user.
The format arguments allow information to be transferred from
the calling portion of the program to the function. They are also known as
parameters formal parenthesis.
The identifiers used as formal arguments are “Local”. in the sense
that they are not recognized outside of the function.
Hence, the name of the formal arguments may be the same as
the names of other identifiers that appear outside the function definition.
· What are
Built-in / Library Functions?
As we know there are a lot of built-in functions for the
users and these are defined in the header files.
Suppose, if you are calling/using a clear screen, colors, wait
for press any key, are the parts of <conio.h> header file.
For example:
clrscr(),
getch(), textcolor() etc.
All types of string functions like string comparing, copying,
making upper case, lower case, etc are the parts of <string.h> header
file.
upper(),
lower(),strcmp(), strcmpi(), strcpy(), strcat() etc.
All mathematics type of functions may be called by including
<math.h> header file.
sqrt(),
sin(), cos(), log() etc.
· What is
User Defined Function?
When we define a function to perform a particular task by
defining a set of identifiers, with a specific data type, the returned value
as per user wish is called UDF (User Define Function).
It may be of two types, (1) No returned value( void type), and
with returned value (prototype).
Example:
To convert an uppercase
to lowercase with the help of user-defined function.
1.
// This User Define Program is coded in
2.
//Turbo for best performance...
3.
#include<stdio.h>
4.
#include<conio.h>
5.
main()
6.
{
7.
char lower, upper;
8.
char utolow(char upper); // This is Declaration part...
9.
clrscr();
10.
printf("enter a upper case character");
11.
scarf("%c",&upper);
12.
lower=utolow(upper);
13.
printf("The Lower case is : %c",lower);
14.
getch(); //pausing screen
15.
}
16.
char utolow(char c1) //This is Definition part...
17.
{
18.
char c2;
19.
c2=(c1>='A' && c1<='Z')?(c1+32):c1;
20.
return(c2);
21.
}
22.
// Code ends here…
Many compilers support a more Comprehensive System for
handling argument specification in function declaration and function
definition. In particular, the proposed ANSI standard permits each of the
argument data types within a function declaration to be followed by the
argument's name that is …
Data-type name(type 1
argument 1, type 2 argument 2, type 3 argument 3, …… type n argument n)
Function declarations in this form are called function
prototypes.
Their use is not mandatory in ‘C’ Function prototypes are
desirable however because they further facilitate error checking between the
calls to a function and the corresponding function definition.
|
Older Method |
Newer Method |
|
Int sample(int, int); Float add(float, float); Void myfunc(char, long, double); Void demo(void); |
Int sample(int a, int b); Float add(float x, float y); Void myfunc(char c1, long n, double d); Void demo(void); |
· What is Void
Function?
In this type of function, there is
no need for a data type and argument in parenthesis. Function Declaration is a void
type meaning no argument and no data type is declared and the function definition
part also is a void type.
1.
#include<stdio.h>
2.
#include<conio.h>
3.
main()
4.
{
5.
clrscr();
6.
add(); // Function declared here as void (no data type
& argument)…
7.
getche();
8.
}
9.
add() //
Function definition with no data type and argument…
10.
{
11.
int a,b;
12.
printf("Enter a value for a : ");
13.
scanf("%d",&a);
14.
printf("Enter a value for b : ");
15.
scanf("%d",&b);
16.
printf("The Sum is : %d",a+b);
17.
//add();
18.
}
· What is
Call by value Function?
This is
older model declaration and definition of a function. This is an example of
also called by value function.
Example 1:
Write a program for Addition by
UDF.
int add(int, int); // Function
declared here…
#include<stdio.h>
#include<conio.h>
main()
{
int a,b,s=0;
clrscr();
printf("Enter a value for a :
");
scanf("%d",&a);
printf("Enter a value for b :
");
scanf("%d",&b);
s=add(a,b); // values are passed here to process…
printf("the Sum is : %d
",s);
getche();
}
int add(int a, int b) // Definition of function that
returns value
{ //
to the function called section.
return (a+b);
}
Example 2:
Write a program for Addition by
UDF.
// This is an illustration of call
by values function(Prototype)
int add(int, int); // Function Declaration....
#include<stdio.h>
#include<conio.h>
int add(int x, int y)
{
// Here X and Y is local variables
for the called function of Prototype.
// and referenced by A and B.
return (x+y);
}
main()
{
int a,b,s=0;
clrscr();
printf("Enter a value for a :
");
scanf("%d",&a);
printf("Enter a value for b :
");
scanf("%d",&b);
s= add(a,b); // Function Definition...
// Here A and B is local variable
for Prototype...
printf("the Sum is : %d
",s);
getche();
}
// Code ends here…
This is an example of multi
variables called by reference.
You can call the function either in
a variable;e called ‘S’ and then print the sum, or you can be called it directly in
printf() as mentioned in the program.
Example 3:
Write a program for Addition by UDF
for multi variables that has to be called in the program.
1.
// Programm Coded in Turboc3 (Dos Box)
2.
// This is an illustration of call by values
function(Prototype)
3.
int add(int*, int*, int*); // Function Declaration for three
variables....
4.
#include<stdio.h>
5.
#include<conio.h>
6.
int add(int *a, int *b, int *c)
7.
{
8.
// Here X and Y is local variables for called function
of Prototype.
9.
// and referenced by A and B.
10.
return (*a+*b+*c);
11.
}
12.
main()
13.
{
14.
int a,b,c;
15.
clrscr();
16.
printf("Enter a value for a : ");
17.
scanf("%d",&a);
18.
printf("Enter a value for b : ");
19.
scanf("%d",&b);
20.
printf("Enter a value for c : ");
21.
scanf("%d",&c);
22.
//add(&a,&b,&c); // Function Definition...
23.
// Here A ,B and C are local variable for Prototype ...
24.
printf("the Sum is : %d
",add(&a,&b,&c)); //
Function Definition...
25.
// you can use this statement directly…
26.
getche();
27.
}
28.
// Code ends here…
· What are
Multi File (separate file) Functions?
There is a type of Function which can be stored in separate
file and called it as per requirement, is known as “Multi File Function”.
You can write the declarative part in a file called “File1.c”
and definition part in a separate file called “File2.c” now compile and call it
together with.
Here we will use an “extern” keyword for both the stored/saved files.
When it is executed, it shows the result.
Write a program for Addition by UDF for multi variables that
has to be called in the prigram.
Example 1:
First file is saved with the name “ F1.c”
1.
// Code written
for the Turboc
2. // Multi file calling function…
3. #include<stdio.h>
4. /* Simple Multifile
program to write "Hello, My dear viewers!" */
5. extern void
output(void);
6. /* External
Function Declaration */
7. main()
8. {
9. output();
10.
return;
11.
}
12.
// Code ends here…
Second file is saved with the name
“ F2.c”
1.
//Code written
for the Turboc
2. // Multi file calling function…
3. #include<stdio.h>
4. extern void
output(void)
5. /* External
Function Definition */
6. {
7. printf("Hello,
My Dear Viewers!/n you are watching me.");
8. return;
9. }
10.
//Code ends here…
How to compile and run together with...?
Answer is here:
Follow these steps if you are in
Turboc (DosBox) for Windows.
1. Open TC.exe.
2. From project select Open Project.
3. Enter the name of project eg: MyProj. prj and Press ok.
4. From project select Add item.
5. Locate all the source files and add them.
6. compile and build.
Yes, you have dun it.
Follow these steps if you are using
Unix OS.
1. Write a program and save it “f1.c” & “f2.c”on the Desktop using (Dos Shell)
command prompt of TC.
- Then type gcc f1.c f2.c
- Then use the command, “Combine” to make and executable
file, like this
Combine f1 f2 <output mode> <new file name>
4. Combine f1 f2 -o
f1_f2
5. -o creates a new file called f1_f2 which is an executable file.
- Now, type the file name only to execute the program.
From the project select Add
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