A computer programs instructions and data have to be in the computers memory for the program to work. There are three principal memory locations on your computer: the central processing unit (CPU), random access memory (RAM), and persistent storage. Computer programs usually use RAM to store instructions and data.
Instructions and data are stored at addresses, represented by a sequential series of numbers . A computer stores information in a series of ones and zeroes. Each one or zero is a bit. However, a computer cannot process information as small as a single bit. Eight bits, or one byte, is the smallest unit of information that a computer can process. Therefore, each address stores one byte of information.
Some information is numeric; other data is textual. Each type of information is referred to as a data type. The principal data type categories are whole numbers, floating-point numbers, and text. However, all data types have in common a characteristic of size, which is the number of bytes required to store information of that data type. A data types size also determines its range, which is the highest and lowest number that can be stored by that data type.
The size of a data type varies depending on the compiler and operating system. You may use the sizeof operator to determine the size of a data type on your particular system.