Fortran has six data types and six corresponding declaration statements: (i.e., using the same name in two declaration statements) is A variable name can be declared only once withinĪ program unit. Declaration statements are nonexecutable therefore, they must precede all executable statements. These data types are specified by means of dec Examples of valid variable namesĮxamples of invalid variable names declaring variables, several data types are used Special characters currency symbol $ and underscore _ as Through Z), and is limited to a maximum of 31 letters orĭigits (0 through 9). A valid variable name must begin with a letter (A Value currently stored in that variable's storage location.Ī variable name identifies a variable within a program At any time, the value of a variable is the Used to explicitly provide initial values for variables.ĭuring execution, values can be changed at any time andĪs many times as needed, simply by assigning a new value Some processors assign initial values to variables, so that all variables are defined at the start of program execution. (32 bits) to store a real variable is referred to as having aĪ variable defines a storage location in the computer's For instance, a computer that uses 4 bytes Computers can store data using either 2, 4, 8, or 16īytes per value. Representation, which is capable of storing only the digits 0 A bit (short for binary digit) is a binary numeric A byte is a unit of storage consisting ofĨ bits. A computer stores data (e.g., the values of variables) in
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