C-Strings (Character Arrays) in C++
STRING: It is an array of type char.
Syntax for declaration
char <array/string name> [max. number of characters to be stored +1];
- The number of elements that can be stored in a string shall always be n-1, if the specified array size is n.
- This is because the NULL character ' \0 ' is reserved for 1 bit, i.e. a backslash zero.
- A string with the character NULL is always terminated.
 |
| C++ String |
Example:
char str[80]; - In the above example, str can be used to store a string with 79 characters.
Initializing a string
- A string can be initialized to a constant value when it is declared.
char str[ ] = "Good";
Or
char str[]={'G','o','o','d','\0'};
Here. 'G' will be stored in str[0], 'o' in str[1] and so on.
Note: If the value is allocated to the entire string at once, the program adds the NULL character automatically at the end of the string. But, if character by character is done, then at the end of the string, we have to insert it.
Reading strings with/without embedded blanks
To read a string without blanks cin can be used
cin>>str;
To read a string with blanks cin.getline() or gets() can be used.
cin.getline(str,80);
-Or-
gets(str);Printing strings
cout and puts() can be used to print a string.
cout<<str:
Or
puts(str);
Note: For gets( ) and puts(), the header file stdio.h has to be included. puts() can be used to display only strings. It takes a line feed after printing the string.
cin
|
gets()
|
| It can be used to take input of a value of any data type. | It can be used to take input of a string. |
| It takes the white space i.e. a blank, a tab, or a new line character as a string terminator. | It does not take the white space i.e. a blank, a tab, or a new line character, as a string terminator. |
| It requires header file iostream.h | It requires the header file stdio.h |
| Example: char S[80]; cout<<"Enter a string:”; cin>>S; | Example: char S[80]; cout<<"Enter a string:"; gets(S); |
cout
|
puts()
|
| It can be used to display the value of any data type. | It can be used to display the value of a string. |
| It does not take a line feed after displaying the string. | It takes a line feed after displaying the string. |
| It requires the header file iostream.h | It requires the header file stdio.h |
| Example: char S[80]="Computers"; cout<<S<<S; Output: ComputersComputers | Example: char S[80]="Computers"; puts(S); puts(S); Output: Computers Computers |
Counting the number of characters in a string and printing it backwards.
#include<iostream.h>
#include<stdio.h>
int main( )
{
char str[80];
cout<<"Enter a string:";
gets(str);
for(int l=0; str[l]!='\0';l++); //Loop to find length
cout<<"The length of the string is : "<<l<<endl ;
for(int i=l-1;i>=0;i--) //Loop to display the string backwards
cout<<str[i];
return 0;
}
Function to count the number of words in a string.
void count(char S[])
{
int words=0;
for(int i=0;S[i]!='\0';i++)
{
if (S[i]==' ')
words++; //Checking for spaces
}
cout<<"The number of words="<<words+1<<endl;
}
Function to find the length of a string.
int length(char S[ ])
{
for(int i=0;S[i]!='\0';i++);
return i;
}
Function to copy the contents of string S2 to S1.
void copy(char S1[ ], char S2[ ])
{
for(int i=0;S2[i]!='\0';i++)
S1[i]=S2[i];
S1[i]='\0';
}
Function to concatenate the contents of string S2 to S1.
void concat(char S1[ ], char S2[ ])
{
for(int l=0;S1[l]!='\0';l++);
for(int i=0;S2[i]!='\0';i++)
S1[l++]=S2[i];
S1[l]='\0';
}
Function to compare strings STR1 to STR2.
The function returns a value>0 if //STR1>STR2, a value<0 if STR1<STR2, and value 0 if STR1=STR2
int compare(char STR1[ ],char STR2[])
{
for(int I=0;STR1[I]==STR2[I] && STR1[I]!='\0'&&STR2[I]!='\0'; I++);
return STR1[I]-STR2[I];
}
To reverse the contents of string S and store it in string Rev
void Reverse(char S[], char Rev[])
{
for(int C1=0; S[C1]!='\0'; C1++);
C1--;
for(int C2=0;C1>=0;C2++,C1--)
Rev[C2]=S[C1];
Rev[C2]='\0';
}
Function to check whether a string S is a palindrome or not
int Palin(char S[])
{
for(int L=0;S[L]!='\0';L++); //To find length
for(int C=0;(C<L/2) && (S[C]==S[L-C-1]);C++);
return (C==L/2)?1:0; //Returns 1 if Palindrome else 0
}
Function to change the case of string S to uppercase
void Upper(char S[])
{
for(int i=0;S[i]!='\0';i++)
S[i] = (S[i]>='a' && S[i]<='z')?(S[i]-32):S[i];
}
Function to change the case of string S to lower case
void Lower(char S[])
{
for(int i=0;S[i]!='\0';i++)
S[i] = (S[i]>='A' && S[i]<='Z')?(S[i]+32):S[i];
}
Function to extract n characters from left side of the string and store it in a different string.
Example: 4 characters from ENVIRONMENT=ENVI
int SLeft(char S[ ], int n, char result[ ])
{
for(int l=0;S[l]!='\0';l++);
if(n<=I) //characters extracted should be <=length
{
for(int i=0;i<n;i++)
result[i]=S[i];
result[i]='\0';
return 1;
}
else
return 0;
}
Function to extract n characters from right side of the string and store it in a different string.
Example: 4 characters from ENVIRONMENT=MENT
int SRight(char S[ ], int n, char result[ ])
{
for(int l=0;S[l]!='\0';l++);
if(n<=I) //characters extracted should be <=length
{
for(int j=0;i=l-n;S[i]!=’/0’;i++,j++)
result[j]=S[i];
result[j]='\0';
return 1;
}
else
return 0;
}
Function to extract n characters from specified location loc of the string and store it in a different string.
Example: 4 characters from third location in string ENVIRONMENT= VIRO
int substring(char S[ ], int n, int loc, char result[ ])
{
for(int l=0;S[l]!='\0';l++);
if(n<=I) //characters extracted should be <=length
{
for(int j=0;i=l-n;S[i]!=’/0’;i++,j++)
result[j]=S[i];
result[j]='\0';
return 1;
}
else
return 0;
}
Some string functions and their uses
#include <stdio.h>
#include <string.h>
int main () {
char str1[12] = "Hello";
char str2[12] = "World";
char str3[12];
int len ;
/* copy str1 into str3 */
strcpy(str3, str1);
printf("strcpy( str3, str1) : %s\n", str3 );
/* concatenates str1 and str2 */
strcat( str1, str2);
printf("strcat( str1, str2): %s\n", str1 );
/* total lenghth of str1 after concatenation */
len = strlen(str1);
printf("strlen(str1) : %d\n", len );
return 0;
}
Expected Output:-
strcpy( str3, str1) : Hello
strcat( str1, str2): HelloWorld
strlen(str1) : 10