CSE2031 Lecture 8

• When creating a struct no space is allocated
  
• typedef
  
  • Make a new type name
    
• Typedef double grade
  
  • "grade" is now a new type
    
  • grade g1 = 3.5
    
    • Grade can be used whenever double is used
      
  • Typedef unsigned int size_t;
    
  • Typedef void (*_sighandler_t)(int)
    
• Pointers to structs
  
  • Structpoint p1;
    
  • Structpoint* pp;
    
  • pp = &p1;
    
  • the name of a struct is not a pointer to the beginning of the variable
    
  • p1.x = 9
    
  • *pp.x = 9 //doesn't work
    
    • Because dot operator has precedence over *
      
  • (*pp).x = 9
    
    • // will properly dereference the struct
      
  • ppàx = 9
    
    • same as (*pp).x =9 only this is proper
      
• self referential structures
  
• if you don't use malloc calloc etc it is put on the stack not the heap
  
• look in back of the book under IO
  
  • c library IO(buffered)
    
  • this is the buffer which input and output is written to
    
  • int getChar(void)
    
  • int putchar(int)
    
  • scanf
    
  • printf
    
• file access
  
  • FILE
    
    • The way you create one is
      
      • FILE * fp
        
      • fp = fopen("filename", mode);
        
      • mode is
        
        • read write and append
          
        • a 2 character string
          
        • char*
          
      • instead of filename you can use
        
        • "rb"
          
        • "wb"
          
        • Ab"
          
        • "rt"
          
        • "wt"
          
        • "at"
          

 

 

 

//creating a structpoint//

--------------------

structpoint{

    int x;

    int y;

 

    }

---------------------------

 

structpoint p1;

p1.x = 5;

p1.y = 6;

------------

or

 

structpoint p1 = {5,6};

----------------------------------

or

structpoint{

int x;

int y;

}

p1;

p1.x = 5

p1.y = 6;

//you can make a new struct doing it this way

--------------------------------------

struct{

int x;

int y;

}

p1.x = 5;

p1.y = 6;

//cannot make a second struct doing it this way

---------------------------------------

typef unsigned int size_t;

typedef void (*_sighandler_t)(int)

--------------------------------------

typedef structpoint {

int x;

int y;

}

point;

/*now "point" is the name of a type

* it can have pint p1;

*instead of structpoint p1

*/

--------------------------------

/* self referential structures*/

struct listNode{

int value;

struct listNode* next;

}

--------------------------------

struct treeNode{

int value;

struct treeNode* left;

struct treeNode* right;

}

------------------------------------

or

--------------------------------------

typedef structTNode* TreePtr

typedef structTNode{

int value;

TreePtr left;

TreePtr right;

}TreeNode

 

-----------------------------------------

TreePtr root = (TreePtr)malloc(sizeof(TreeNode));         // - do not do this instead - sizeof(int) + 2*sizeof(TreePtr)

root->value = 5;

root -> right = (TreePtr)malloc(sizeof(TreeNode));

root -> right ->value=2;

root -> right->right =null;

root -> right ->left = null;

/*creates a binaryTree with root starting point at 5 pointing to a 2 on its right side that has no strings after it*/

--------------------

struct item{

double price;

char name[50];

}

item x1;

strcpy(x1,name, "Notebook");

---------------------------

struct item{

double price;

char* name;

}

item x1;

x1.name = "notebook";

-----------------------------------

fprintf(fp,...);

fscanf(fp,...);

fclose(fp);

ferror(fp);

intfeof(fp); //if you reached end of file on that file

fflush(fp);

fseek(fp,...);

fsetpos(fp,...);

--------buffered standard output under this line--

stdin

stdont

stderr

---------unbuffered under this line---

 

STDIN_FILENO         0

STDOUT_FILENO        1

STDERR_FILENO        2

--------------------------------------------------

#include <stdio.h>

#include <unistd.h>

int main(void)

{

printf("a");

write(1, "X", 1);

fprintf(stdout, "B");

write (1,"Y", 1);

printf("C");

write(1, "Z\n", 2);

printf("\n");

return 0;

/*output is

XYZ

ABC

this is becuase it's buffered

/*

}