Arrays are similar to ideas in mathematics
An array stores many values in memory using only one name.
"Array" in programming means approximately the same thing as
array, matrix, or vector does in math.
Unlike math, you must declare the array and allocate
a fixed amount of memory
for it.
Subscripts are enclosed in square brackets [].
xi in mathematics is
x[i] in C++.
Declaring an array
Declare the array arrays size and the type of elements.
All elements must be the same type. Write the
element type name, the name of the array variable, then the size
enclosed in square brackets ("[]").
int scores[100]; // array of 100 ints, scores[0] to scores[99]
char name[40]; // array of 40 chars, name[0] to name[39]
Subscripts start at zero
Subscript ranges always start at zero.
This is a bad idea because it isn't the way that
humans normally count, but it's the way that C, C++, Java
and many other languages do it.
Altho the an element with subscript zero is allocated,
there is no need to use it, so you can program using
subscripts from 1 up. However, most C++ programs use
subscripts starting at 0, and we'll use the convention
here.
Length of an array
There is no way to find the length of an array. You must keep the
size (both the maximum, and currently filled size) of the array in variables.
For example,
const int MAXSIZE = 366;
...
int temperature[MAXSIZE];
int numOfTemps = 0; // number of entries in temperature
Example -- adding all elements of an array
These statements read values into an array and sum them.
Assume fewer than 1000 input values.
int a[1000]; // Declare an array of 1000 ints
int n = 0; // number of values in a.
. . .
while (cin >> a[n]) {
n++;
}
. . .
int sum = 0; // Start the total sum at 0.
for (int i=0; i<n; i++) {
sum = sum + a[i]; // Add the next element to the total
}