Functions That Convert strings to Integral Types

Consider an example of converting a string to an integral value. Assuming the string:

the following statement converts the beginning of the string to the int value 100 and stores that value in convertedInt:

Each function that converts a string to an integral type actually receives three parameters—the last two have default arguments. The parameters are:

• A string containing the characters to convert.

• A pointer to a size_t variable. The function uses this pointer to store the index of the first character that was not converted. The default argument is a null pointer, in which case the function does not store the index.

• An int from 2 to 36 representing the number’s base—the default is base 10.

So, the preceding statement is equivalent to

Given a size_t variable named index, the statement:

converts the binary number "100" (base 2) to an int (100 in binary is the int value 4) and stores in index the location of the string’s letter "h" (the first character that was not converted).