CS 192
Lecture 13
Winter 2003
January 5-6, 2004
Dr. Shafay Shamail
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Pointers Part 2-Introduction to Computer Programming-Lecture Slides, Slides of Computer Programming
Dr. Mehandi Nandakumar delivered this lecture at Baddi University of Emerging Sciences and Technologies for Introduction to Computer Programming course. Its main points are: Void, Pointer, Pointers, Multidimensional, Arrays, String, Dynamic, Allocation, Memory, Leak
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CS 192Lecture 13Winter 2003
January 5-6, 2004Dr. Shafay Shamail
Void Pointer
int age = 20;int *ageptr = &age;void *vptr = (void *)ageptr;int *newptr = (int *)vptr;Can’t do:vptr++vptr—vptr + 2As the base type of vptr is not known
Initializing Multi-Dimentional Arrays
static int example[5][3] ={
static int example[5][3] ={
Initializing Multi-Dimensional Arraysstatic int example[][3][2] ={
}; 4-by-3-by-2 array
Arrays of Pointers …
-^ Two dimensional string pointers e.g. C++ dictionary^ char
*keyword[][2]
=
{ "for",
"for(initialization;
condition;
increment)",
"if",
"if(condition)
...^
else^
...",
"switch",
"switch(value)
{^ case-list
}",
"while",
"while(condition)
...",
//^ add
the^
rest^
of^ the
C++^
keywords
here
"",^ ""
//^
terminate
the^
list^
with^
nulls
}; int main(){ char
str[80];int i;cout <<^ "Enter
keyword:
";
cin^ >>
str; for(i=0;
*keyword[i][0];
i++)
if(!strcmp(keyword[i][0],
str))
cout^
<<^ keyword[i][1]; return
0; }
Array of Strings vs. Array of Pointers
^ char
movies[5][20]
{“Godfather”,“Maula
Jatt”, “A^ Fish
Called
Wanda”,
“Blade
Runner”, “Spiderman”}; ^ char
*movies[5]
{“Godfather”,“Maula
Jatt”, “A^ Fish
Called
Wanda”,
“Blade
Runner”, “Spiderman”};
- each column is 20characters wide due tothe longest moviename• wasted space• the strings are placedcontiguously inmemory withoutwasting space• pointers in the array^ movie
point to them
int xptr=new int;xptr = 73;int x2ptr = new int;x2ptr = 65;
Dynamic Allocation
What is wrong here?int xptr = new int;xptr = 73;int x2ptr;x2ptr=65;
Dynamic Allocation
//What is wrong here?int xptr = new int;xptr
int *x2ptr = new int;x2ptr
= xptr;
*x2ptr
//memory leak
Dynamic Allocation
int *myptr = new int(73);cout << *myptr;delete myptr;
Dynamic Allocation
Array of Pointers
const int RSIZE = 4;const int CSIZE = 6;int * iarray[RSIZE];for(int k=0; k<RSIZE; k++){ iarray[k] = new int [CSIZE];if (iarray[k] == NULL){
cerr << “Memory Allocation Error…\n”;cerr << “Exiting …\n”;exit(-1); } }
A two dimensional
array ofRSIZE*CSIZE
iarray 0 1 2 3
Double and Tripple Pointers
int a = 20;int *ip = &a;int **ipp = &ip;int ***ippp = &ipp;cout << a << endl;cout << ip << *ip << endl;cout << ipp << *ipp << **ipp << endl;cout << ippp << *ippp << **ippp << ***ippp << endl;