Question

Suppose that account identification numbers are written using nine digits, for example, 972-54-5990. What C variable type should be used to store these? Why?

Answer 1

we can use "int" or "unsigned int" or "long" data type because range of integer lies between -2,147,483,648 to 2,147,483,647.

size of data types depend on compiler which one you are using. If OS is 32 bit or 64 bit then it will take 4 bytes and if OS is 16 bit then size will be 2 bytes.

int            2 or 4 bytes   -32,768 to 32,767 or-2,147,483,648 to 2,147,483,647
unsigned int    2 or 4 bytes    0 to 65,535 or 0 to 4,294,967,295
long             4 bytes        -2,147,483,648 to 2,147,483,647
unsigned long    4 bytes    0 to 4,294,967,295

So use any of above data types for storing 9 digits number.