Program Description Language (PDL)
Program description language (PDL) is free-format English-like text which describes the flow of control in a program. PDL is not a programming language but rather is
a tool which helps the programmer to think about the logic of the program before the program has been developed. Commonly used PDL keywords are described as follows.
START-END
Every PDL program description (or subprogram) should begin with a START keyword and terminate with an END keyword. The keywords in a PDL code should be highlighted in bold to make the code more clear. It is also a good practice to indent program statements between PDL keywords in order to enhance the readability of the code.
Use IF, THEN, ELSE, and ENDIF keywords to describe the flow of control in a program.
Notice that the REPEAT-UNTIL loop is always executed at least once, and more than once if the condition at the end of the loop is not met.