Converting Bases

We would like to :

Integer 489 is $4x10^2 + 8x10^1 + 9x10^0$
Strings have two functions to access the characters in them
- char stringVar.at(size_t)
- char stringVar[size_t]
- at() does bounds checking and thows excptions for array index o ut of bounds error.
- [] does not.
The ascii characters set represents the characters we use
- These are 8 bit numbers
- Digits are numbered sequentially
  - '0' = 48
  - '1' = 49
  - '2' = 50
  - ...
  - '9' = 57
- So '3' - '0' = 3.
The size_t stringVar.size() function returns the number of characters in a string.

int sum{0};
string num{"489"}
size_t i;
for(i = 0; i < num.size(); ++i) {
    sum = sum * 10 + num[i] - '0';
}