TABLE OF CONTENTS 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.
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.
<b class="bold"> START ....... ....... END</b>
For normal sequencing in a program, write the statements as short English text as if you are describing the program.
Turn on the LED Wait 1 second Turn off the LED
Use IF, THEN, ELSE, and ENDIF keywords to describe the flow of control in a program.
<span class="beginpage"> pagenum="289"><a name="746"></a><a name="page289"></a></span><b class="bold"> IF</b> switch = 1 <b class="bold">THEN</b> Turn on LED 1 <b class="bold">ELSE</b> Turn on LED 2 ...
