1. Characters and Strings
A character constant is an integer value represented as a character in single quotes.
‘z’ represents the integer value of z (122 in ASCII code).
‘\n’ represents the integer value of z (10 in ASCII code).
characters and strings manipulation

2. characters and strings manipulation
A string is a series of characters treated as a single unit.
String literals (string constants) are written in double quotations.
“99 Main Street” (a street address literal)
A string in C++ is an array of characters ending with the null character (‘\0’).
A string is accessed via a pointer to the first character (like array).
characters and strings manipulation

3. characters and strings manipulation
String definition
char color[] = ”blue”;
char *colorptr = ”blue”;
char color[] = {‘b’, ‘l’, ‘u’, ‘e’, ‘\0’};
characters and strings manipulation

4. characters and strings manipulation
String definition
char word[20];
cin>>word;
Note that the string is no longer than 19 characters.
We can use cin.getline to read a line (more than one word).
characters and strings manipulation

5. characters and strings manipulation
String definition
char sentence[80];
cin.getline(sentence, 80, ‘\n’);
The cin.getline has ‘\n’ as a default value, so the preceding function call could have been written as:
cin.getline(sentence, 80);
characters and strings manipulation

6. characters and strings manipulation
String manipulation
Header file: <string.h>
char *strcpy( char *s1, const char *s2);
Copies s2 into s1, the value of s1 is returned.
char *strcat(char *s1, const char *s2);
Append the string s2 to the string s1, the value of s1 is returned.
characters and strings manipulation

7. characters and strings manipulation
String manipulation
int strcmp(const char *s1, const char *s2);
Compares s1 with s2, returns a value of zero, less than zero or greater than zero if s1 is equal to, less than or greater than s2, respectively.
int strlen(const char *s);
Determines the lengthof string s.
characters and strings manipulation

8. characters and strings manipulation
Lexical Analyzer
#include <iostream.h>
#include <string.h>
void main() {
char line[100], lexeme[20], ch;
strcpy(lexeme,""); //lexeme=nothing
strcpy(line,""); //line=nothing
cout<<"enter a sentence? ";
cin.getline(line, 100);
int i=0; //line counter
int k=0; //lexeme counter
ch=line[i];
characters and strings manipulation

9. characters and strings manipulation
while ( i<=strlen(line)) {
if (ch==' '|| ch==';'|| ch=='\0')
lexeme[k]='\0';
cout<<lexeme<<endl;
strcpy(lexeme,""); k=0; //reset lexeme
i++; }
else
lexeme[k]=ch; k++; //add ch to lexeme
ch=line[i];
characters and strings manipulation

10. characters and strings manipulation
Structure Definition
Structures are user defined data types built using elements of other types.
struct student {
long number;
char *name;
int mark[3];
float average; };
characters and strings manipulation

11. characters and strings manipulation
Structure Definition
Structures variables are declared like variables of other types:
student s, y; //one structure
student std[10]; //array of structures
student *studentptr; //point to a structure
characters and strings manipulation

12. Accessing Members of Structures
Members of a structure (or of a class) are accessed using the member access operator - or dot operator - (.), the arrow operator (->).
The dot operator accesses a structure member via the variable name for the object.
cin>>s.name;
cout<<std[1].average;
s.average=(s.mark[0]+s.mark[1]+s.mark[2])/3;
characters and strings manipulation

13. Accessing Members of Structures
The arrow operator accesses a structure member via a pointer to the object.
cin>>studentptr->name;
cout<<studentptr->average;
characters and strings manipulation

14. characters and strings manipulation
Example
Example: Write C++ program reads in the name, number and average of 10 students using array of structures then prints this list. The program contains 2 functions for reading and printing.
characters and strings manipulation

15. characters and strings manipulation
#include <iostream.h>
#include <string.h>
struct student {
char name[20];
long number;
float average; };
void reading(student *, const int);
void printing(student *, const int);
int main()
const int size=100;
student stud[size];
reading(stud, size);
printing(stud, size);
return 0; }
characters and strings manipulation

16. characters and strings manipulation
void reading(student *s, const int size) {
for (int i=0; i<=size-1; i++)
cout<<"Enter Name,Number and Average\n";
cin>>s[i].name>>s[i].number>>s[i].average; }
void printing(student *s, const int size)
cout<<s[i].name<<"\t"<<s[i].number<<"\t“
<<s[i].average<<endl;
characters and strings manipulation