Presentation is loading. Please wait.

Presentation is loading. Please wait.

CSE 251 Dr. Charles B. Owen Programming in C1 Pointers, Arrays, Multidimensional Arrays Pointers versus arrays – Lots of similarities How to deal with.

Published byBuck Farmer Modified over 8 years ago

Similar presentations

Presentation on theme: "CSE 251 Dr. Charles B. Owen Programming in C1 Pointers, Arrays, Multidimensional Arrays Pointers versus arrays – Lots of similarities How to deal with."— Presentation transcript:

1 CSE 251 Dr. Charles B. Owen Programming in C1 Pointers, Arrays, Multidimensional Arrays Pointers versus arrays – Lots of similarities How to deal with 2D, 3D, multidimensional arrays (for storing matrices and other 2D or 3D data!)

2 CSE 251 Dr. Charles B. Owen Programming in C2 Review: Pointers Pointers are variables that store memory addresses int a = 15; int *b = &a; printf(“%x %x %d\n”, b, &b, *b); // prints effffa94 effffa98 15 AddressMemory 0xeffffa94 0xeffffa98 Name a b 15 0xeffffa94

3 CSE 251 Dr. Charles B. Owen Programming in C3 int number; int *ptr = &number; printf(“Enter an integer: ”); scanf(“%d”, &number); printf(“Enter another integer: “); scanf(“%d”, ptr); printf(“Number = %d, *ptr = %d\n”, number, *ptr); Using pointers in scanf function Read & as “at” Don’t have to put & before ptr. It’s already an “at”. Example output:

4 CSE 251 Dr. Charles B. Owen Programming in C4 int multiply( int *, int); int main() { int number = 3; int *ptr = &number; printf(“1: %d\n”, multiply( &number, 2 ) ); printf(“2: %d\n”, multiply( ptr, 3 ) ); } int multiply (int *a, int factor) { return (*a) * factor; } Passing pointers (addresses) to functions

5 CSE 251 Dr. Charles B. Owen Programming in C5 Review: Arrays An array is a contiguous chunk of memory to store multiple values int grades[]={74,59,95,85,71,45,99,82,76}; grades 745995857145998276 0xeffffa000xeffffa040xeffffa080xeffffa0c0xeffffa100xeffffa140xeffffa18 0xeffffa1c 0xeffffa20 index012345678 A

6 CSE 251 Dr. Charles B. Owen Programming in C6 int sumArray( int [], int); int main() { int list[] = {1, 2, 3, 4}; printf(“Sum = %d\n”, sumArray( list, 4 )); } int sumArray (int list[], int arraySize) { int sumvalue = 0; for (int i=0; i<arraySize; i++) sumvalue += list[i]; return sumvalue; } Passing arrays to functions

7 CSE 251 Dr. Charles B. Owen Programming in C7 Array Name The array name is a pointer to the first element of the array 1234 [1][2][3][0] list ffe2de0cffe2de10ffe2de14ffe2de18 Output: ffe2de0c ffe2de0c 1 int list[]={1,2,3,4}; printf(“%x, %x, %d”, list, &list[0], *list);

8 CSE 251 Dr. Charles B. Owen Programming in C8 Pointers and Arrays int *p, int list[]={1,2,3,4}; p = list; /* equivalent to p = &list[0] */ printf(“%d\n”, *p); /* prints the value “1” */ 1234 [1][2][3][0] list p You can use a pointer to access the array

9 CSE 251 Dr. Charles B. Owen Programming in C9 Pointer and [] Any pointer to a block of memory can use the [] syntax, even if it is not declared as an array! 1234 [1][2][3][0] List P int *p, int list[]={1,2,3,4}; p = list; printf(“%d\n”, p[2]); // prints 3 int *v; and int v[]; /* Mean the same thing */

10 CSE 251 Dr. Charles B. Owen Programming in C10 Array indexing [] Indexing an array is just a way of finding a particular address in that block 1234 [1][2][3][0] list ffe2de0cffe2de10ffe2de14ffe2de18 list + 2 int list[] = {1,2,3,4}// array of 4 ints printf(“%d”, list[2]); This is equivalent to printf(“%d”,*(list+2)); *list – Contents pointed to by list *(list + 2) – Contents at list[2] B

11 CSE 251 Dr. Charles B. Owen Programming in C11 Pointer Arithmetic When we add to a pointer, such as (p + 1), we don’t literally add 1 to the pointer address Instead we add one “address” to the pointer

12 CSE 251 Dr. Charles B. Owen Programming in C12 Pointer Arithmetic p int list[] = {1, 2, 3, 4}; int *p = list; /* same as p = &list[0] */ printf(“%x”,p); /* prints ffe2de0c */ 1234 ffe2de0cffe2de10ffe2de14ffe2de18

13 CSE 251 Dr. Charles B. Owen Programming in C13 Pointer Arithmetic p int list[] = {1, 2, 3, 4}; int *p = list; /* same as p = &list[0] */ printf(“%x”,p); /* prints ffe2de0c */ p = p + 1; /* p increases by 4 */ printf(“%x”,p); /* prints ffe2de10 */ 1234 ffe2de0cffe2de10ffe2de14ffe2de18 Think of pointer arithmetic as add 1 “location” instead of one byte or address.

14 CSE 251 Dr. Charles B. Owen Programming in C14 Pointer Arithmetic p double list2[] = {1.0, 2.0, 3.0}; double *p = list2; /* same as p = &list2[0] */ printf(“%x”, p); /* prints ffe2de0c */ 1.0 ffe2de0cffe2de10ffe2de14ffe2de18 2.03.0 ffe2de1cffe2de20 C

15 CSE 251 Dr. Charles B. Owen Programming in C15 Pointer Arithmetic P double list2[] = {1.0, 2.0, 3.0}; double *p = list2; /* same as p = &list2[0] */ printf(“%x”,p); /* prints ffe2de0c */ p = p + 1; /* P increases by 8 bytes */ printf(“%x”,p); /* prints ffe2de14 */ 1.0 ffe2de0cffe2de10ffe2de14ffe2de18 2.03.0 ffe2de1cffe2de20

16 CSE 251 Dr. Charles B. Owen Programming in C16 Pointer Arithmetic on Arrays *(list+1) references the next element in the array (equivalent to list[1]) Be careful: *(++list) works too but now we have lost our pointer to the beginning of the array!!! – Equivalent to: list = list + 1; *list;

17 CSE 251 Dr. Charles B. Owen Programming in C17 sizeof() operator int i; int *ptr4i = &i; int IntArray[] = {1, 2, 3, 4, 5}; double j; double *ptr4j = &j; double doubleArray[] = {1.0, 2.0, 3.0, 4.0,5.0}; printf("Sizeof integer is %d bytes\n", sizeof(int)); printf("Sizeof double is %d bytes\n", sizeof(double)); printf("Sizeof i is %d bytes\n", sizeof(i)); printf("Sizeof pointer for i is %d bytes\n", sizeof(ptr4i)); printf("Sizeof j is %d bytes\n", sizeof(j)); printf("Sizeof pointer for j is %d bytes\n", sizeof(ptr4j)); printf("Sizeof intArray is %d bytes\n", sizeof(intArray)); printf("Sizeof doubleArray is %d bytes\n", sizeof(doubleArray)); Returns the number of bytes needed to store a variable or a data type

18 CSE 251 Dr. Charles B. Owen Programming in C18 sizeof() operator

19 CSE 251 Dr. Charles B. Owen Programming in C19 When we pass an array When we pass an array, we are passing the array address int sumArray( int [ ], int); int main() { int list[] = {1, 2,3, 4); … sumArray( list, 4 ); …

20 CSE 251 Dr. Charles B. Owen Programming in C20 When we pass an array This will work too (because array name is a pointer to the beginning of the array) int sumArray( int *, int); int main() { int list[] = {1, 2,3, 4); … sumArray( list, 4 ); …

21 CSE 251 Dr. Charles B. Owen Programming in C21 When we pass an array But this DOES NOT work! int sumArray( int *, int); int main() { int *list = {1, 2, 3, 4); … sumArray( list, 4 ); …

22 CSE 251 Dr. Charles B. Owen Programming in C22 Pointers 1 Indexing an array is just a way of finding a particular address in that block 1234 [1][2][3][0] list ffe2de0cffe2de10ffe2de14ffe2de18 list + 2 int list[] = {1,2,3,4}// array of 4 ints printf(“%d”, list[2]); This is equivalent to printf(“%d”,*(list+2)); *list – Contents pointed to by list *(list + 2) – Contents at list[2]

23 CSE 251 Dr. Charles B. Owen Programming in C23 2-D Arrays int cave[ArraySize][ArraySize]; 1234 5678 9101112 13141516 0 1 2 3 0123 Row Column

24 CSE 251 Dr. Charles B. Owen Programming in C24 2D Arrays int myMatrix[3][4] = { {1,2,3,4},{5,6,7,8},{9,10,11,12} }; 1234 5678 9101112 myMatrix[0][1]  2 myMatrix[2][3]  12 myMatrix[row][col] 0123 Column 0 1 2 Row

25 CSE 251 Dr. Charles B. Owen Programming in C25 Physically, in one block of memory int myMatrix[2][4] = { {1,2,3,4},{5,6,7,8} }; 12345678 Array elements are stored in row major order Row 1 first, followed by row2, row3, and so on ffe2de0cffe2de10ffe2de14ffe2de18ffe2de1cffe2de20ffe2de24ffe2de28 row 1row 2

26 CSE 251 Dr. Charles B. Owen Programming in C26 2D Array Name and Addresses 12345678 myMatrix: pointer to the first element of the 2D array myMatrix[0]: pointer to the first row of the 2D array myMatrix[1]: pointer to the second row of the 2D array *myMatrix[1] is the address of element myMatrix[1][0] ffe2de0cffe2de10ffe2de14ffe2de18ffe2de1cffe2de20ffe2de24ffe2de28 int myMatrix[2][4] = { {1,2,3,4},{5,6,7,8} };

27 CSE 251 Dr. Charles B. Owen Programming in C27 Accessing 2D Array Elements int myMatrix[2][4] = { {1,2,3,4}, {5,6,7,8} }; 12345678 Indexing: myMatrix[i][j] is same as *(myMatrix[i] + j) (*(myMatrix + i))[j] *((*(myMatrix + i)) + j) *(&myMatrix[0][0] + 4*i + j)

28 CSE 251 Dr. Charles B. Owen Programming in C28 Declaration #define ROWS 3 #define COLS 5 int table[ROWS][COLS]; void display (table);

29 CSE 251 Dr. Charles B. Owen Programming in C29 void display( int x[ROWS][COLS] ) { for (int i=0; i < ROWS; i++) { for (int j=0; j < COLS; j++ ) { printf(" x[%d][%d]: %d", i, j, x[i][j]); } printf("\n"); } printf("\n"); } 2D Arrays often require nested loops – two variables

30 CSE 251 Dr. Charles B. Owen Programming in C30 Table A = { {13, 22, 9, 23}, {17, 5, 24, 31, 55}, {4, 19, 29, 41, 61} }; Table B = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 }; 1322923? 175243155 419294161 12345 678910 11121314?

31 CSE 251 Dr. Charles B. Owen Programming in C31 passing 2d arrays In passing a multi-dimensional array, the first array size does not have to be specified. The second (and any subsequent) dimensions must be given! int myFun(int list[][10]);

32 CSE 251 Dr. Charles B. Owen Programming in C32 #define ROWS 3 #define COLS 5 int addMatrix( int [ ][COLS] ); int main() { int a[][COLS] = { {13, 22, 9, 23, 12}, {17, 5, 24, 31, 55}, {4, 19, 29, 41, 61} }; printf(“Sum = %d\n”, addMatrix( a ) ); } int addMatrix( int t[ ][COLS] ) { int i, j, sum = 0; for (i=0; i<ROWS; i++) for (j=0; j<COLS; j++) sum += t[i][j]; return sum; } 1

Download ppt "CSE 251 Dr. Charles B. Owen Programming in C1 Pointers, Arrays, Multidimensional Arrays Pointers versus arrays – Lots of similarities How to deal with."

Similar presentations

A Short Review Arrays, Pointers and Structures. What is an Array? An array is a collection of variables of the same type and placed in memory contiguously.

A Short Review Arrays, Pointers and Structures. What is an Array? An array is a collection of variables of the same type and placed in memory contiguously.
Programming and Data Structure

Programming and Data Structure
Kernighan/Ritchie: Kelley/Pohl:

Kernighan/Ritchie: Kelley/Pohl:
ICS103: Programming in C Searching, Sorting, 2D Arrays

ICS103: Programming in C Searching, Sorting, 2D Arrays
1 ICS103 Programming in C Lecture 16: 2-Dimensional Arrays.

1 ICS103 Programming in C Lecture 16: 2-Dimensional Arrays.
©2004 Brooks/Cole Chapter 8 Arrays. Figures ©2004 Brooks/Cole CS 119: Intro to JavaFall 2005 Sometimes we have lists of data values that all need to be.

©2004 Brooks/Cole Chapter 8 Arrays. Figures ©2004 Brooks/Cole CS 119: Intro to JavaFall 2005 Sometimes we have lists of data values that all need to be.
1 Arrays In many cases we need a group of nearly identical variables. Example: make one variable for the grade of each student in the class This results.

1 Arrays In many cases we need a group of nearly identical variables. Example: make one variable for the grade of each student in the class This results.
1 Chapter 9 Arrays and Pointers. 2  One-dimensional arrays  The Relationship between Arrays and Pointers  Pointer Arithmetic and Element Size  Passing.

1 Chapter 9 Arrays and Pointers. 2  One-dimensional arrays  The Relationship between Arrays and Pointers  Pointer Arithmetic and Element Size  Passing.
1 CS 201 Array Debzani Deb. 2 Having trouble linking math.h? Link with the following option gcc –lm –o test test.o.

1 CS 201 Array Debzani Deb. 2 Having trouble linking math.h? Link with the following option gcc –lm –o test test.o.
Pointers Example Use int main() { int *x; int y; int z; y = 10; x = &y; y = 11; *x = 12; z = 15; x = &z; *x = 5; z = 8; printf(“%d %d %d\n”, *x, y, z);

Pointers Example Use int main() { int *x; int y; int z; y = 10; x = &y; y = 11; *x = 12; z = 15; x = &z; *x = 5; z = 8; printf(“%d %d %d\n”, *x, y, z);
Chapter 8 Multidimensional Arrays C Programming for Scientists & Engineers with Applications by Reddy & Ziegler.

Chapter 8 Multidimensional Arrays C Programming for Scientists & Engineers with Applications by Reddy & Ziegler.
Pointers CSE 2451 Rong Shi.

Pointers CSE 2451 Rong Shi.
C Static Arrays Pepper. What is an array? Memory locations – same type – next to each other (contiguous) – Same name – Indexed by position number of type.

C Static Arrays Pepper. What is an array? Memory locations – same type – next to each other (contiguous) – Same name – Indexed by position number of type.
CSEB114: PRINCIPLE OF PROGRAMMING Chapter 8: Arrays.

CSEB114: PRINCIPLE OF PROGRAMMING Chapter 8: Arrays.
ARRAY Prepared by MMD, Edited by MSY1.  Introduction to arrays  Declaring arrays  Initializing arrays  Examples using arrays  Relationship with pointers.

ARRAY Prepared by MMD, Edited by MSY1.  Introduction to arrays  Declaring arrays  Initializing arrays  Examples using arrays  Relationship with pointers.
1 Pointers and Arrays. 2 When an array is declared,  The compiler allocates sufficient amount of storage to contain all the elements of the array in.

1 Pointers and Arrays. 2 When an array is declared,  The compiler allocates sufficient amount of storage to contain all the elements of the array in.
 2000 Prentice Hall, Inc. All rights reserved. 1 6.2Arrays Array –Group of consecutive memory locations –Same name and type To refer to an element, specify.

 2000 Prentice Hall, Inc. All rights reserved Arrays Array –Group of consecutive memory locations –Same name and type To refer to an element, specify.
Arrays Array –Group of consecutive memory locations –Same name and type To refer to an element, specify –Array name –Position number Format: arrayname.

Arrays Array –Group of consecutive memory locations –Same name and type To refer to an element, specify –Array name –Position number Format: arrayname.
Problem Solving and Program Design in C (5th Edition) by Jeri R. Hanly and Elliot B. Koffman Chapter 6 (Pointers) © CPCS 202 12-10-1429.

Problem Solving and Program Design in C (5th Edition) by Jeri R. Hanly and Elliot B. Koffman Chapter 6 (Pointers) © CPCS
Chapter 8: Arrays Introduction to arrays Declaring arrays Initializing arrays Examples using arrays Relationship with pointers Array passing to a function.

Chapter 8: Arrays Introduction to arrays Declaring arrays Initializing arrays Examples using arrays Relationship with pointers Array passing to a function.

Similar presentations

Ads by Google