1. Sequence structure: In the sequence structure, instructions are executed in the order in which they are encounterd.
2. Loop/Iteration structure: The loop (or iteration) structure provides for the repetition of one or more instructions for as long as a given situation, referred to as a condition, exists.
3. Selection structure: A condition is tested, and one of two alternative courses of action is selected depending on whether the condition is ture or false.

A group of instructions that performs a limited processing test, such as printing a portion of a report, reading an input record, or calculating a square root.
subroutine can be classified into two types: 

1. Internal subroutines: An internal subroutine is part of the program that uses it.
2. External subroutines: External subroutines are used for tasks that more than one program is likely to want performed.

In modular programming, the program is broken down into modules (pieces), each of which performs a single, limited function and is written and debugged separately from other modules.

The person or group who whome will use the output produced by the computer.

Programming without the use of branch instruction that is called GOTOless programming.