Variables and Data Types in Programming

Study Notes

Data types describe what values can be held by an item, how the item is stored in memory, and what operations can be performed on it.
Variables are named memory locations whose contents can change over time; they need to be declared with a data type and identifier.
Data types include numeric, string, and integer; numeric types can be either integers or floating-point numbers.
Constants are values that do not change during program execution; they can be literal constants, string constants, or unnamed constants.
Initializing a variable means giving it a starting value.
A variable not yet initialized contains an unknown value called garbage.

Modules are subunits of a programming problem, also known as subroutines, procedures, functions, or methods.
Modularization is the process of breaking down a large program into modules, which allows for abstraction, easier division of work, and simpler code reuse.

Abstraction is the process of focusing on essential properties while ignoring nonessential details.
Modules allow programmers to work on a program by focusing on the specific function of their assigned module without needing to understand the details of other modules.

Modularization makes it easier to divide a large programming project among multiple programmers.
This allows for faster development as skilled professionals can work on specialized modules simultaneously.

Modules function as self-contained units that can easily be transported and reused in other programs, which increases code efficiency and speeds up development.

Modules can declare their own variables and constants, which are visible and usable within the module only.
Global variables and constants are declared at the program level and can be used by all modules in the program; their use should be minimized to avoid errors.

The mainline logic of most procedural programs typically follows a general structure that includes global variable declarations, housekeeping tasks, a detail loop, and end-of-job tasks.

A hierarchy chart visually represents the relationships between modules in a program, showing how they call each other.
It helps plan the overall structure of a program before writing code and serve as documentation.

Use program comments: Comments are written explanations that clarify program logic and act as documentation for readers.
Choose identifiers carefully: Consider descriptive names, pronounceable names, and judicious use of abbreviations when selecting variable and module identifiers.
Design clear statements: Aim for readability and ease of understanding when writing statements within programs and modules.
Write clear prompts and echo input: Prompts inform users of the program's expectations, while echoing input confirms user input and avoids errors.
Maintain good programming habits: Follow best practices throughout the programming process, including planning, flowcharting or pseudocoding, desk-checking, and thoughtful variable naming.