Data Structure and C Part-6. Naming a Function Any valid variable-name can be given to the...
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Transcript of Data Structure and C Part-6. Naming a Function Any valid variable-name can be given to the...
Naming a Function
• Any valid variable-name can be given to the user-defined function.
• The main program itself is considered as a function in C.
• Whenever a C program is executed, execution starts from the function.
• So there should be only one main function.
Example of Code Program# include <stdio.h>main( ){
------ Calling
------Function
------}
------}calculation()int…….;{
------ Called
------Function------}
Structure of a Function
The general structure is return type function name (list of parameters)
Syntax:
parameter declaration.{ Statements :}
Body of the Function
• The body of the function contains a variable declaration part, processing and a return statement.
• The variables declared within the body of a function are called ‘local variables’.
• These variables can be used or referred to only within the body of that function and hence the name.
• These variables have no meaning outside the body of that function.
• The body of the function is given within braces.
Example:cube ( int x ){ int cubes; cubes = x*x*x;
return (cubes); }
The Return-Statement
• The calculation part can contain either assignment statement or any valid arithmetic logic expressions.
• If there is a value that has to be returned to the calling function
• The return statement is used.
The general syntax is :return [value];
Example:# include <stdio.h>main( ){
int a ;a = retfun( );printf(“a = %d”,a)getch( );
}
retfun( ){
return(1);}
The output is a = 1
Example of Code Program
Function Declaration
• Any C function by default returns an int value.
• If a function should return a value other than integer.
• then it is necessary to explicitly mention so in the calling function declaration or function prototype.
# include <stdio.h>main ( ){float x, y ;
float div (float a, float b);
printf (“enter 2 number”);
scanf (“%f%f”,&x,&y);
printf (“The div value is %f” ,div (x,y);
getch ( );}Float div (a,b)Float a,b;{
Return(a/b);}
Void Function Type •If the function returns no value then it is called void function.
•Such function must be declared as a void function.
•In general void is an empty data type.General form •Void function name ( )
Example-1
#include<Stdio.h>#include<Conio.h>void welcome (char name [ ]);{Printf (“ Welcome % s” name);}
Example-2
# include <stdio.h>void fun1 (void);void fun2 (viod);main ( ){
clrscr ( ) ;fun1 ( ) ;getch ( ) ;
}
void fun2(void){
Printf (“C Programming”);}
Parameter in FunctionsA function is called by specifying its name followed by a list of arguments.
When a function is invoked, the formal parameters are initialized to the actual parameters used in the function call operator .
The corresponding arguments in the function Program are called actual parameter.
Declarationmain ( ){
a = area (l,b);}{
area (x,y)
……}
main ( ){
int a,b;result = mul (a,b):
……
} mul(i,j); int i,j;{
…… }
LIBRARY FUNCTIONS
C offers a rich collection of library functions.
Any of these functions can be called from any
C program.
To invoke these functions we have to include
the appropriate header file in the program.
Utility Functions
• Utility Functions is symbol by<stdlib.h>.
• It is an header file.
• Utility Functions has servral types. Following are given below
atof ( )• This is used to convert a string into a floating-point value. • The general format is atof (string);Example:main ( ){
char a [20] = “222.33”;float c;C = atof (a);
} The output will be C = 222.33
atoi ( )This function is used to convert a string into an integer value..The general form is: atoi (string);Example:main ( ){
char a[20] = “2233”;int c;c = atof(a) + 5;
}The output is C= 2238
Mathematical Functions
• Mathematical Functions Symbol <math.h> • It has several types. Following are given
below;-
floor ( )• This function is used to find the floor of a
value x.
• The floor of x is the first smaller integer. The general format is:
• Floor (x);• Example:-• floor (2,9) = 2• floor (-2.1) = 3
ceil ( )
This function returns the round value of the nearest highest integer. The general format is:
ceil (x);Example:ceil(2.6) = 3 ceil(5.2) = 6 ceil(-4.3) = -4
pow ( )
This function is used to find xy. The general format is:
Pow (x,y);Example:pow (2.3);The output is 8.
String Function
• String Function is symbol <string.h>
• It also using character and words.
• These functions are for string manipulations.
These functions can be classified according to
their performance as follows:-
Joining of two strings
1) strcat 2) strncati.strcat: This function is used to add two strings. The result is stored in the destination string that is the first string. The general form is: strcat(string 1, string 2);
ii. strncat: This function is similar to ‘strcat()’ except. That it binds only n characters of string 2 with string 1. The general form is: strncat(string 1, string 2, n);
Conversion of Strings
1) strlur: This function is used to convert a string containing uppercase to lowercase. The general Format is: strlwr (string);
2) strupr: This function is used to convert a string containing lowercase to uppercase. The general format is: strupr (string);3) strrev: This function is used to reverse the string. The general format is strrev (string);
• 4) strset: This function is used to replace all
the characters in a string with a particular given character.
The general format is: strset(string, char);
where the string will be replaced by the character.
5) strnset: This function is similar to strset ( ). The only difference is that we can specify the number of characters to be replaced in the given string. The general format is: strnset (string, char , n);
Comparison of string
1) strcmp This function is used to compare the
two strings. The function is case sensitive. The general format is:• strcmp (string 1, string2);• Example:• string 1 = “Canada”• string 2 = “Africa”
2) strncmp :
This function will compare just n
characters of string 2 with string 1.
This is case sensitive.
The general format is:
stricmp(string 1, string 2, n);
3) stricmp : This function is similar to strcmp(). It is an except that this is non-case sensitive. The general format is: stricmp(string 1, string 2);
Other String Functions
1) Strlen This function is used to find the
length of the string. This function will not count null-
terminating character. The general format is: strlen(string);
2) strcpy This function is used to copy string 2 to string 1 including the null terminating character of string. The general format is: strcpy (string1, string2); Here string 1 is the destination where the string 2 will be copied. After the execution the old characters in string 1 will be completely erased.
3) Strncpy This function is similar to strcpy(), except that it copies n characters on string 2 to string 1. The general format is: strncpy(string1, string, n);
Character Class Test Functions Character class test functions is symbol by <ctype.h>.
1)isalnum ( ) Tests whether a character is an alphabet or a number. Isalnum(int c);
• 2. islower ( )• Test whether a charcter is a lower case or
not.• Islower (int c);• 3. isupper ( )• Tests whether the charcter is a uppercase.• Isupper(int c);
2. islower ( ) Test whether a character is a lower case or not. Islower (int c);
3. isupper ( ) Tests whether the charcter is a uppercase. Isupper(int c);