Strctures,strings,pointers
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Transcript of Strctures,strings,pointers
STRUCTURE, POINTER, STRING
Nikhil Dev S.B
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Disclaimer: This presentation is prepared by trainees ofbaabtra.com as a part of mentoring program. This is notofficial document of baabtra.com – Mentoring Partner
OVER VIEW
1.STRUCTURES
2.POINTERS
3.STRING
STRUCTURES
Collection of data items of different types using a single name,user defined datatype.
Grouping several pieces of related information together, array canstore only single type data.
E.g1. It can handle student_name,roll_number and marks under asingle name student.
E.g2. book: author ,price ,year. customer: name, telephone, city, category.
DEFINING A STRUCTUREstruct tag-name{
datatype member1;datatype member2;. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
};
E.g. struct book_bank{
char title[20];char author[15];int pages;float price;
};
DEFINING STRUCTURE TYPE
VARIABLE• Declare a variable of type structure to access the members of structure.• struct book_bank
{char title[20];char author[15];int pages;float price;
}; struct book_bank book1,book2,book3;
• arrays of strucctures: struct book_bank book[3];
Another type of declaration:
• struct book_bank{
char title[20];char author[15];int pages;float price;
} book1,book2,book3;
ACCESSING STRUCTURE MEMBERS
• We access and assign values to structure members.
• Access can be done by member operator ‘ . ’ also known as dot operator period operator or by -> (pointer to structure)
•E.g. book1.price=250; book1.pages=300;scanf(“%s”,book.title);
STRUCTURE INITIALIZATION• struct
{int weight;float height;
} student ={60,180.75};
• struct st_record{
int weight;float height;
} ;struct st_record student1={60,180.75};
POINTERS
• Derived data type in C.
• Contain memory address as their values. i.e. It stores memory address of another variable.
• Pointers reduce length of program.• Declare as int *ptr• Initialize pointer as null int *ptr=0 or int *ptr=NULL
& (address operator)Returns address of operand
int y = 5;
int *yPtr;
yPtr = &y; //yPtr gets address of y
yPtr “points to” y
yPtr
y
5
yptr
500000 600000
y
600000 5
Address of yis value of yptr
• Declare an array int b[5] and a pointer int * bPtrbPtr = b; Array name actually a address of first element
ORbPtr = &b[0].
C uses two pointer operators,
Indirection operator (*) – to get the value belongs to the address.Address-of-operator (&) – ampersand symbol, means return the address of a variable.
When & operator is placed before the name of a variable, it will returns the memory address of the variable instead of stored value.
#include<stdio.h>#include<conio.h>void main(){
int x,*p,y;
x=10;
p=&x;
y=*p; // accessing x through p OUTPUT
*p=20; // assigning 20 to x P: 2686734 (Address of x)
printf("\n\tp:%d",p); *p: 20
printf("\n\t*p:%d",*p); y: 10
printf("\n\ty:%d",y);
getch();
}
STRING• Sequence of characters treated as single data item
• There is no string type, we implement strings as arrays of characters in C.
• E.g. “Welcome”;
DECLARE A STRING
• char str[10]; // str is an array of 10 chars or a string
• char str[10]=“Welcome” // Declare and initialize a string.
• char str[10]= { ‘w’, ’e’ , ’l’ , ‘c’ , ‘o’ , ‘m’ , ‘e’ }
READING A STRING
• scanf(“%s”,str); // read a string, no need of & sign.
• gets(str); // read a string with white spaces.
• scanf(“%5s”, str); // read only five characters even str can hold 10.
• for(i=0;i<10;i++){
scanf(“%c”,&str[i]) // read by character-by character;}
Writing string to screen
• printf(“%s”, str);• puts(str);
STRING FUNCTION• strcpy(s1, s2) – copies s2 into s1 (including ‘\0’ as last char)
• strncpy(s1, s2, n) – same but only copies up to n chars of s2
• strcmp(s1, s2) – returns a negative int if s1 < s2, 0 if s1 = = s2 and a
positive int if s1 > s2
• strcat(s1, s2) – concatenates s2 onto s1 (this changes s1, but not s2)
• strlen(s1) – returns the integer length of s1
Thank you...
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