Function
Large program broken down into smallest unit as function.
A
function is a subprogram that acts on data and often returns a value.
Function in C++
Type of function
There are broadly two types of functions
1. Built-in (or library) function
2. User -defined function
1. Built -in function
These functions are part of compiler
package. These are part of standard library mode available by the compiler.
For eg. exit (), sqrt(), pow(), strlen()
etc.
Header File Categorization
|
Header File
|
Function
|
Standard input/output function
|
stdio.h
|
gets(),puts()
|
String function
|
string.h
|
strcpy(),strcat(),strlen(),
strcmp(),strcmpi(),strrev(),
strupr(),strlwr()
|
Character function
|
ctype.h
|
isalnum(),isalpha(),isdigit(),
islower(),isupper(),tolower(),
toupper()
|
Mathematical function
|
math.h
|
fabs(),pow(),sqrt(),sin(),cos(),
abs()
|
Other function
|
stdlib.h
|
randomize(),random()
|
2.
User -defined function
The user defined functions are created by
you i.e. programmer. These functions are created as per the requirements of the
program.
Ex.
int absval(int a)
{
return (a<0? -a: a);
}
Standard Input/output Function (stdio.h)
1.gets()
The gets() function accept a string of characters entered
from the keyboard and placed them in the string variable mentioned with it.
Ex. char name[21];
gets(name);
The string name stores 20 valid character and one extra for
null character ‘\0’.
2.puts()
The function puts() write a string on the screen and
advances the
cursor to the newline. For this, stdio.h header file is used.
Character function
1.isalnum()
This function returns non zero if its argument is a letter
or a digit otherwise return zero.
Syntax
int isalnum(int c);
Ex. char ch;
cin>>ch;
if(isalnum(ch))
{
cout<<”alphanumeric”;
}
2.isalpha
This function is used to check whether the given argument is
an alphabet. Ii returns zero when the argument does not have any of them.
Syntax
int isalpha( int c);
Ex.
char ch;
if(isalpha (c))
{
cout<<”it is
alphabetic”;
}
3.isdigit()
This function is used to check the character whether it is
between 0-9 or a decimal. It returns zero when argument is not a decimal or an
integer in the given range.
Syntax
int isdigit(int c);
Ex.
char ch;
if(isdigit (ch))
{
cout<< “It is
digit”;
}
4.islower()
This is used to check the function arguments for lowercase
letters (a-z). It returns zero if lowercase letters are not found.
Syntax
int islower(int c);
Ex.
if( islower(ch))
{
cout<<”lowercase letter”;
}
5.isupper()
isupper() character function is used to check if the
argument contains uppercase letters(A-Z) ,if not this functions returns zero.
Syntax
int isupper(int c);
Ex.
if (isupper(ch))
{
cout<<”uppercase character”;
}
6.toupper()
This function returns
the uppercase of the parameter if it’s a letter, otherwise returns the same parameter without
any change.
Syntax
int toupper(int ch);
Ex.
#include<iostream.h>
#include<ctype.h>
main()
{
char ch=’a’;
cout<<toupper(ch);
}
7.tolower()
This function returns the lowercase of the parameter if it’s
a letter, otherwise returns the same parameter without any change.
Syntax
int
tolower(int ch);
Ex.
char ch=’A’;
cout<<tolower(ch);
String Function(string.h)
1.strcpy()
strcpy() manipulates function is used to copy the characters
of one string to another.
Syntax
char*strcpy(char*destination,
const char*source);
Ex. #include<iosream.h>
#include<string.h>
void main()
{
char *s1=”ace”;
char *s2=”bag”;
char *s2=”bag”;
strcpy(s1, s2);
cout<<s1;
}
2.strcat()
This function concatenates a copy of s2 to s1 and terminates
s1 with a null.s1 should be large enough to hold both original contents and
those of s2.
Syntax
char
*strcat(char *str1, const char *str2);
Ex.
char *s1=”one”;
char *s2=”two”;
strcat(s2, s1);
cout<<s2;
3.strlen()
It is used to find the length of a string between starting
character and the terminating null character. The null is not counted.
Syntax
int strlen(const char *str);
Ex. char s1[50];
strcpy(s1, “My
name is Alex”);
cout<<strlen(s1);
output-15
4.strcmp()
This function alphabetically compares two strings and
returns -ve value is s1 is less than s2; 0 if s1 is equal to s2, and >0 (+ve
value) if s1 is greater than s2.
Syntax
int strcmp(cont char*str1, const
char *str2);
ex. char *s1=”Ace”
;char *s2=”Bag”;
cout<<strcmp(s2,s1); (>0)
cout<<strcmp(s1,s2); (<0)
5.strcmpi()
Compare string without case sensitivity.
Syntax
int strcmpi(const char *s1, const char *s2);
ex.
if
(0==strcmpi(“hello”, “HELLO”))
cout<<”this string are equivalent”;
else
cout<<”this
string are not equivalent”;
6.strrev()
This function reverses all the characters in string(except
for the terminating null).
Syntax
char
*strrev(char *str);
Ex. char *str1=”Ace”;
cout<<strrev(str1);
7.strupr()
This function will convert all the lower case characters in
the string to uppercase.
Syntax
char
*strlwr(char *str);
Ex. char *s1=”HELLO”;
cout<<strlwr(s1);
Mathematical function (math.h)
1.fabs()
fabs() is a mathematical function that returns the absolute
value of the given argument(real number)
Syntax
float fabs(float num);
output
Ex. cout<<fabs(2.5426); 2.542600
cout<<fabs(-8.6); 8.600000
2.pow()
This function returns the “base” value raised to the “exp”
power. A domain error is triggered if the “base” value is “zero” and the
exponent is less than or equal to zero.
Syntax
float pow(float base, float exp);
float pow(float base, int exp);
Ex.
#include<iostream.h>
#include<math.h>
int main()
{
cout<<”2 to
the power of 2 is:”<<pow(2,2)<<endl;
cout<<”4 to the power of 2
is:”<<pow(4,2)<<endl;
}
3.sqrt()
This Mathematical function that returns the square root of
the given “num” value.
Syntax
float
sqrt(float num);
double
sqrt(double num);
long
double sqrt(long double num);
Ex.
#include<iostream.h>
#include<math.h>
int main()
{
float r;
r=sqrt(4);
cout<<”square root of 4:”<<r;
return();
}
4.sin()
This function that returns sin value of the given argument
represented in radian.
Syntax
float sin(float arg);
Ex.
#include<iostream.h>
#include<math.h>
int main()
{
cout<<”The sine
value of 60 degree is:”<<sin(60)<<endl;
cout<<”The sine
value of 90 degree is”<<sin(90)<<endl;
return 0;
}
Result
The sine value of 60
degree is: -0.304811
The sine value of 90
degree is: 0.893997
5.cos()
This mathematical function returns the cosine value for the given
radians.
Syntax
float cos (float arg);
double cos(double arg);
long double cos(long double arg);
Ex.
#include<math.h>
const double
PI=3.14159265
int main()
{
cout<<”The
cosine value of 0 is:”<<cos(0)<<endl;
cout<<”the cosine value of PI is:”<<cos(PI)<<endl;
return 0;
}
6.abs()
This function
represents the absolute value of integer number.
Syntax
int abs(int n);
Ex.
int c=-15;
cout<<abs(c);
Other Function (stdlib.h)
random() and randomize() function is just like rand() and
srand() to generate random no.
In order to generate in user’s specified range we can use
two more macros, also defined in stdlib.h they are random() and randomize().
To generate a random number between 0 to 9
you can write
random(10);
Because random() function generate random number maximum up
to n-1 and between L-U.
So.
random(U-L+1) +L
Ex.
#include<iostream.h>
#include<stdlib.h>
#include<conio.h>
#include<time.h>
main()
{
int num, i;
randomize();
for (i=0; i<5;
++i)
{
num=random(14-5+1)
+5;
cout<<num<< ‘ ‘;
}
getch();
}
Output: 1st
run 7 8
8 14 5
2nd run 13 6
13 9 6
3rd run 9 9
6 7 10
4th
run 5 13
11 12 5
This post is about function in c++. In the next post we will discuss the topic User -Defined Function.
This post is about function in c++. In the next post we will discuss the topic User -Defined Function.
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