In Sequence - the order of these must be the same in both lists. The scope of an identifier is the program or subprogram in which it is declared. An identifier is available in subprograms unless a local identifier of the same name has been declared. An identifier cannot be referenced before it has been declared. Blocks for subprograms - The trick is to think of these blocks as nested.
Subprograms occur within programs.
Using global variables and constants Generally, don't use global variables . In subprograms, deal only with parameters and local variables. This will reduce sideeffects. It also makes tracing problems much simplier, as you do not have to watch a variable throughout the run of a program to know what is happening to it. Global variables will only be altered by the main program.