Lecture 2: arrays and pointers
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This document provides an introduction to arrays and pointers for beginner programmers. It explains what arrays and pointers are, how to declare and initialize them, and includes examples of common operations like accessing element values, taking addresses, and dereferencing pointers. Demo code is provided to illustrate summing array elements, finding maximum values, reversing an array, and printing two-dimensional arrays and pointers. The document aims to explain basic array and pointer concepts without advanced mathematics to help beginners learn programming fundamentals.
![Arrays - 1D
● int test[10]; // space for 10 ints
● 0-based indexing
● Index from 0 to (size - 1)](https://image.slidesharecdn.com/placementprep-arraysandpointers-140904065659-phpapp01/85/Lecture-2-arrays-and-pointers-6-320.jpg)
![Demo #4
Reverse the contents of an array.
int arr[10]={1,2,3,4,5,6,7,8,9,10};](https://image.slidesharecdn.com/placementprep-arraysandpointers-140904065659-phpapp01/85/Lecture-2-arrays-and-pointers-11-320.jpg)
![Arrays - 2D (Matrix)
● int test_score[x][y]
Row Index
Column Index
int test_score[10][4]](https://image.slidesharecdn.com/placementprep-arraysandpointers-140904065659-phpapp01/85/Lecture-2-arrays-and-pointers-12-320.jpg)
![Demo #6
char mat[6][3];
0 1 2
0 e o e
1 o e o
2 e o e
3 o e o
4 e o e
5 o e o](https://image.slidesharecdn.com/placementprep-arraysandpointers-140904065659-phpapp01/85/Lecture-2-arrays-and-pointers-14-320.jpg)
![Arrays as pointers
int arr[7];
Array Index
Data
arr
0 1 2 3 4 5 6
- 22 - 33 - 44 - 55 - 66 - 77 - 88
0014 0018 0022 0026 0030 0034 0038
arr + 1 arr +2 arr + 6
Address](https://image.slidesharecdn.com/placementprep-arraysandpointers-140904065659-phpapp01/85/Lecture-2-arrays-and-pointers-27-320.jpg)
![0 1 2 3 4 5 6
- 22 - 33 - 44 - 55 - 66 - 77 - 88
0014 0018 0022 0026 0030 0034 0038
arr[0] is same as *(arr + 0) is same as -22
&(arr[0]) is same as (arr + 0) is same as 0014
arr[1] is same as *(arr + 1) is same as -33
&(arr[1]) is same as (arr + 1) is same as 0018
arr[5] is same as *(arr + 5) is same as -77
&(arr[5]) is same as (arr + 5) is same as 0034
Array Index
int arr[7]
Address
arr](https://image.slidesharecdn.com/placementprep-arraysandpointers-140904065659-phpapp01/85/Lecture-2-arrays-and-pointers-28-320.jpg)
Lecture 2: arrays and pointers
- 1. Placement Preparation Arrays & Pointers Shobhit Chaurasia B.Tech, CSE
- 2. Target Audience People who have no prior coding experience, didn’t take CS101 seriously but want to learn some basics of coding quickly. If you know how write a program to sum up numbers in an array, and you DO NOT faint on seeing int ***ptr, then please don’t your waste time here; this tutorial is not for you.
- 3. Data types ● int : -1000, -5, 0, 10, 2014 ● char : a, @, + ● float : -10.35, 2.578 ● bool : True/False
- 4. More Data types ● Array - {1,2,3,4} ● String - “Ghissu” ● Pointers
- 5. Arrays ● Array is a collection of objects.
- 6. Arrays - 1D ● int test[10]; // space for 10 ints ● 0-based indexing ● Index from 0 to (size - 1)
- 7. Array - initialization 1D 2D
- 8. Demo #1 Store first 10 +ve integers in an array and print them.
- 9. Demo #2 Sum up all the numbers in an array.
- 10. Demo #3 Find the max. number in an array.
- 11. Demo #4 Reverse the contents of an array. int arr[10]={1,2,3,4,5,6,7,8,9,10};
- 12. Arrays - 2D (Matrix) ● int test_score[x][y] Row Index Column Index int test_score[10][4]
- 13. Demo #5 Output contents of a 2D int array.
- 14. Demo #6 char mat[6][3]; 0 1 2 0 e o e 1 o e o 2 e o e 3 o e o 4 e o e 5 o e o
- 15. Arrays - 3D
- 16. Address of Variables ● int x = 10; //value of x is 10 ● address of variable x is &x x 10 0x7fff4d84231c Variable Name Data/Content Address of variable
- 17. Demo #7 Print the value and address of a float
- 18. Pointers Pointer is a variable that contains memory address. ptr 0x7fff4d84231c p 0x7fff01f8239c f 0x00abcd12209
- 19. ptr 0x7fff4d84231c p f 0x243f01f8239a 0x00abcd12209 10 0x7fff4d84231c s 0x243f01f8239a 0.3 0x00abcd12209
- 21. Demo #8 &x returns the address of variable x
- 22. Pointer Dereferencing int *ptr; ptr = &x; cout<<ptr; cout<<*ptr; Pointer Declaration Making ptr point to x (x MUST be int) Will print address of x Will print the value stored at x 6 0x7fff4d84231c ptr x
- 23. Pointer Dereferencing *ptr returns the value stored at the memory location pointed to by ptr
- 24. Demo #9 ➔ Show and explain 9.cpp ➔ Ask them to reproduce the code without looking
- 25. NULL Pointer int *ptr = NULL; //good coding practice ptr
- 26. Pointer to Pointer int x = 10; int *p = &x; int **q = &p; q 0x32 0x74 p 0x66 0x32 x 10 0x66
- 27. Arrays as pointers int arr[7]; Array Index Data arr 0 1 2 3 4 5 6 - 22 - 33 - 44 - 55 - 66 - 77 - 88 0014 0018 0022 0026 0030 0034 0038 arr + 1 arr +2 arr + 6 Address
- 28. 0 1 2 3 4 5 6 - 22 - 33 - 44 - 55 - 66 - 77 - 88 0014 0018 0022 0026 0030 0034 0038 arr[0] is same as *(arr + 0) is same as -22 &(arr[0]) is same as (arr + 0) is same as 0014 arr[1] is same as *(arr + 1) is same as -33 &(arr[1]) is same as (arr + 1) is same as 0018 arr[5] is same as *(arr + 5) is same as -77 &(arr[5]) is same as (arr + 5) is same as 0034 Array Index int arr[7] Address arr
- 29. To be continued ... ● Dynamic memory allocation ● C-style strings. ● strcmp, strcat etc.