CompTIA A+ Certification All-in-One Exam Guide

A way to think of a string is as a sequence of characters, like c – o – w.
Most programming languages require that you identify a string with ‘single’
or “double” quotes, so ‘cow’ or “cow” in this example. While only some
characters are valid integers, all characters can be valid in a string. Every
programming language dictates actions that the computer can perform on
strings (like joining two strings together, breaking one string into pieces,
checking how many characters are in a string, and so on). While arithmetic
dictates that you can’t add 3 + cow (probably because it would upset the
cow), you can combine “brown” + “cow” and create a “brown cow” (and
have a happier cow).
EXAM TIP The CompTIA A+ objectives mention only two basic data
types—strings and integers. Some languages have additional data types for
more specific circumstances (like a special type for dates, or fractional
numbers), but you won’t need to know them for the exam.
Here’s the next cool concept. Numbers are characters too, just like words.
Numbers, therefore, can show up in strings—and programming languages
have to treat number characters differently when quoted or not quoted. A
programming language determines what to do with a telephone number
without quotes and with quotes, for example, like these:
In the first case, a computer wouldn’t have any choice but to compute the
result of 281 minus 922 minus 4166, which results in –4807 (an integer data
type). In the second case, a computer would keep intact a string containing
the phone number to my office. Yes, our refrigerator is running.
Variables
As soon as the computer thinks it’s done with this value (whether it’s –4807
or “281-922-4166”), it will forget it. If you need to use it more than once, you
have to tell the computer to save it. Most programming languages tell the