2.2 - programming techniques

2.2 - programming techniques

1. variables

   • Variables are named locations in memory that are used to store temporary values that can change as the program is run
   • In some programming languages, variables need to be declared before they can be used to store data. Declaring a variable means to state its name (identifier) and the type of data that it will contain

2. constants

   • Constants are named locations in memory that are used to store values that do not change throughout the program's execution
   • Constants are very useful for representing values that you don't want to have to re-type throughout the program, either because they are awkward or because you would have to replace many instances of a fixed value if you were to change this value during your design of the program.
   • Constants are very much like variables, except that their assigned values do not change during the execution (running) of a program.

3. arrays

   • arrays is a a data structure, that stores multiple values , under a single identifier
   • Arrays are really useful when you have lots of related data that you don't want to store in multiple variables.
   • Arrays are made up of multiple slots (elements), each of which can contains an item of data.
   • Each array is made up of a number of elements
   • Arrays are fixed sized data structures
   • You must specify the size of the array when you declare it
   • Sufficient memory is reserved for the array to store its data when it is declared

4. selection

   • controls the flow of an algorithm by checking whether a condition is met or not before determining which steps should follow.

5. sequence

   • each step is executed in the order that it is written. All algorithms are made up of at least a basic sequence of instructions.

6. iteration

   • controls the flow of an algorithm by repeating a set of instructions either for a fixed number of times or whilst a set condition is met.
   • Indefinite iteration - a block of code that will repeat whilst a specified condition is true. This is often called condition-controlled iteration and is done with WHILE and DO...WHILE loops.
   • Definite iteration - a block of code that will repeat a known number of times. This is often called count-controlled iteration and is done with FOR loops.

7. The value stored by variable or constant can be set or recalled by using the identifier name of the variable. The process of setting a value to a variable or constant is called assignment