1. CS-161 Computer Programming Lecture 14: Arrays I
Spring 2015 (Sections A & B)
Saqib Rasheed

2. Arrays They are special kind of data type In C++ each array has name
size
They occupy contagious area of memory

3. Storage of an array in memory
C[0]
C[1]
C[2]
C[3]
C[4]
C[5]
C[6]
C[7]
C[8]
C[9]
Name
... 35 59 24
memory
Index

4. Declaration of Arrays arrayType arrayName[numberOfElements ];
For example ,
int age [ 10 ] ;
More than one array can be declared on a line
int age [10] , height [10] , names [20] ;
Mix declaration of variables with declaration of arrays
int i , j , age [10] ;

5. Defining Arrays When defining arrays, specify Examples:
Name
Type of array
Number of elements
arrayType arrayName[ numberOfElements ];
Examples:
int week[ 10 ];
float myArray[ 3284 ];
Defining multiple arrays of same type
Format similar to regular variables
Example:
int b[ 100 ], x[ 27 ];

6. Arrays Array To refer to an element, specify Format:
Name of array (Note that all elements of this array have the same name, week)
Array
Group of consecutive memory locations
Same name and same type
To refer to an element, specify
Array name
Position number
Format:
arrayname[ position number ]
First element at position 0
n element array named week:
week[ 0 ], week[ 1 ]...week[ n–1]
Saturday temp
Sunday temp
Monday temp
Tuesday temp
Wednesday temp
Thursday temp
Friday temp
week[0]
week[1]
week[2]
week[3]
week[4]
week[5]
week[6]
Position number of the element within array week

7. Arrays Array elements are like normal variables
week[ 0 ] = 3;
cout << week[ 0 ];
Perform operations in subscript. If x equals 3
week[ ] = week[ 3 ] = week[ x ]
Static entry (same size throughout program execution)
Some arrays are dynamic (that can be shrink and increase at execution time) called Dynamic Array.

8. Initializers Initializers
int n[ 5 ] = { 1, 2, 3, 4, 5 };
If not enough initializers, rightmost elements become 0
int n[ 5 ] = { 0 }
If too many a syntax error is produced
If size omitted, initializers determine it
int n[ ] = { 1, 2, 3, 4, 5 };
5 initializers, therefore 5 element array

9. Referring to individual elements of a Array
We can refer the individual elements of an array using subscripts (the number in brackets following the array name).
The number specifies the element’s position in the array.
All the array elements are numbered, starting at 0 to size.
Example:
week [2].
cin >> week[2];
Saturday temp
Sunday temp
Monday temp
Tuesday temp
Wednesday temp
Thursday temp
Friday temp
week[0]
week[1]
week[2]
week[3]
week[4]
week[5]
week[6]
cout << “The temperature is “ << week [2];

10. Entering Data into the Array
Example:
for (int day = 0; day < 7; day ++ ) {
cout << “Enter temperature for day“ << day+1;
cin >> week [day]; }

11. Displaying Data from Array
Example:
for (int day = 0; day < 7; day ++ ) {
cout <<Week[day]; }

12. Reading Data from the Array
To calculate the average of the week’s temperature using array (here is the code).
int sum = 0;
for (int day = 0; day < 7; day++ ){
sum += week[day]; }
cout << “Average is “ << sum/7;

13. Example
#include<iostream.h> void main() { int marks [5]; int total=0,i; cout<< "Please enter marks of five students:\n"; for (i=0; i<5; i++) { cin >> marks[i]; } total + = marks[i]; float classavg = total/5; for(int j=0; j<5; j++) { cout<< "Students # "<< j+1<< “ scored "<<marks[j]<<" marks"; cout<< "Class average is "<<classavg<<endl;

14. Class Task
Write a program to store and display the mathematical table of given number using arrays.
Write a program to reverse elements in an array of size 10.
Write a program that reads 10 integers from user and then print the largest and smallest integer using arrays.