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# CS201-15 - Introduction to Programming Lecture 15 In...

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Unformatted text preview: Introduction to Programming Lecture 15 In Today’s Lecture Pointers and Arrays Manipulations Pointers Expression Pointers Arithmetic Multidimensional Arrays Pointer String and Array Pointers and Arrays int y [ 10 ] ; Starting Address of Array y 0 1 2 3 4 5 6 7 8 9 [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] The name of the array is like a pointer which contain the address of the first element. Declaration of a Pointer Variable int y [ 10 ] ; int *yptr ; yptr is a pointer to integer yptr = y ; Declaration of a Pointer Variable 0 1 2 y[3] 3 4 5 6 7 8 9 [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] int y [ 10 ] ; int *yptr ; yptr = y ; yptr ++ ; location 3000 3004 3008 3012 3016 y[0] y[1] y[2] y[3] y[4] pointer variable yPtr In this case yptr is a pointer to integer so now when we increment yptr it points to the next integer Example 1 #include<iostream.h> main ( ) { int y [ 10 ] ; int *yptr = y ; yptr = y ; cout << yptr ; yptr ++ ; cout << yptr ; } yptr = y ; is same as yptr = &y [ 0 ] ; …….. yptr = &y [ 2 ] ; #include<iostream.h> main ( ) { int y [ 10 ] ; int *yptr ; yptr = y ; cout << yptr ; yptr ++ ; cout << *yptr ; } Example 2 Example 3 main ( ) { int x = 10 ; int *yptr ; yptr = &x ; cout << yptr ; cout << *yptr ; *yptr ++ ; increment whatever yptr points to } Pointer Arithmetic *yptr + 3 ; This Is an Expression cout << *yptr ; *yptr += 3 ; Pointer Arithmetic yptr = &x ; yptr ++ ; Pointer Arithmetic int x =10 ; int *yptr ; yptr = &x ; *yptr += 3 ; yptr += 3 ; Decrementing *yptr ­­ Pointer Arithmetic int *p1 ,*p2; ….. p1 + p2 ; Error Pointer Arithmetic int y [ 10 ] , *y1 , *y2 ; y1 = &y [ 0 ] ; y2 = &y [ 3 ] ; cout << y2 ­ y1 ; Pointer Arithmetic int y [ 10 ] ; int *yptr ; yptr = y [ 5 ] ; cout << *( yptr + 5 ) ; Pointer Comparison if ( y1 > y2 ) if ( y1 >= y2 ) if ( y1 == y2 ) Pointer Comparison if ( *y1 > *y2 ) Example int y [ 10 ] ; int *yptr ; yptr = y ; cout << y [ 5 ] ; cout << ( yptr + 5 ) ; cout << *( yptr + 5 ) ; int que [ 10 ] ; int y [ 10 ]; int *yptr ; yptr = y ; yptr = que ; Example location 3000 3004 3008 3012 3016 v[0] v[1] v[2] v[3] v[4] pointer variable vPtr Strings String Initialization char name [ 20 ] ; name [ 0 ] = ‘A’ ; name [ 1 ] = ‘m’ ; name [ 2 ] = ‘i’ ; name [ 3 ] = ‘r’ ; name [ 4 ] = ‘\0’ ; String Initialization Strings is always terminated with \0 String Initialization Array must be one character char name [ 20 ] = “Amir” ; space larger than the number of printable character which are to be stored. Example 4 char string1 [ 20 ] = “Amir”; char string2 [ 20 ] ; char *ptrA, *ptrB ; prtA = string1 ; prtB = string2 ; while ( *ptrA != ‘\0’ ) { *ptrB++ = *ptrA++; } *ptrB = ‘\0’ ; String Copy Function myStringCopy ( char *destination , const char *source ) { while ( *source != ‘\0’ ) { *destination++ = *source++ ; } *destination = ‘\0’ ; } In Today’s Lecture Pointers and Arrays Pointer Arithmetic String Arrays Manipulation of Arrays ...
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