Program structure and layout

Program structure

Example

----------------------------------
--      sum_prod -      sum and product
----------------------------------

with ...;
use  ...;

procedure program_name  is

    declare I/O packages
    
    declare constants & variables used

begin --        program_name  

    statements

end program_name ;

Structure

header:

• identifying comments
• what does this procedure depend on

declarations:

• name
• libraries needed
• variables, constants, procedures

statements:

• program instructions

reserved words have special meaning

Layout Conventions

Common layout convention makes programs easier for others to read, understand, maintain (and mark!)

Basic conventions:

• one statement (one thought) per line
• break long lines into readable segments
• indent lines to show different parts of program
• blank lines separate parts of the program
• comments help readers understand program