Algorithmic Constucts

Algorithmic Constucts

1. Selection & Condition

   • A selection statement uses a condition to select, or determine, the next line of the program that is to be executed.
     • IF
       • The 'if' statement is one of the most basic and simplest controls flow statements. We can use the ‘if’ statement when we want to execute a group of one or more script statements only when a particular condition is met.
     • IF ELSE
       • As we know, the ‘if’ statement allows us to execute a set of statements only when a particular condition is true. However, if we want to execute another set of statements when the condition is false, then we can use the ‘if / else’ statement.

2. Modularisation

   • Modularisation is used to reduce the complexity of a system by deconstructing it into independent units or modules.
   • Pseudocode example
     • FUNCTION delivery_charge CALCULATE totalCost IF (totalCost > $10)  THEN OUTPUT  ‘no delivery charge’ ELSE OUTPUT  ‘$5 delivery charge’ ENDIF OUTPUT  ‘thankyou’ END FUNCTION

3. Iteration

   • A FOR loop is used when it is known exactly how many times to go round the loop
     • Iteration is also called repetition and is used when something is repeated over and over again, so anything where the program goes round in a loop. Typically programmed using code such as WHILE, REPEAT and FOR statements. See the example of Pseudocode using a FOR loop to write out numbers 1 to 10

4. Sequence

   • A sequence is a number of instructions that are processed one after the other.
     • Each step is an instruction to be performed. Sequencing is the order in which the steps are carried out.

5. Assignment

   • Assignment is used to store the value of an expression into a variable.
     • Assignment is the way that a variable is told to remember a certain value.