External Procedures

External procedures

• are parametrised blocks of code that perform a specific task; this section of code is written once, and can be reffered to as many times as needed;
• are ``independent'' units which may be compiled separately;
• communicate with other program units via arguments, returned values (functions only), and global variables (to be discussed another lecture);
• can be used as arguments in other procedure calls.

Advantages

• avoid code duplication (when same task appears several times in our program);
• lead to modularization of programs. The general principle of dividing the problem into subproblems, and managing the subproblems separately, can be naturally implemented using procedures;
• make software reusable (pieces can be used later in a different context);

In F95 there are 2 types of external procedures,

1. functions, and
2. subroutines.